Honda Prelude 1997 2.2L DOHC MFI, Prelude 1997 2.2L DOHC Workshop Manual

honda :: Honda Prelude Type-SH L4-2156cc 2.2L
DOHC (VTEC) MFI (1997)

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Information on the Immobilizer System

Technical Service Bulletin # 96-051

Antitheft - Information on the Immobilizer System

Bulletin No. 96-051

Issue Date NOV 4, 1996

Model 1997 PRELUDE

Applicable To ALL

File Under ELECTRICAL
Information on the Immobilizer System

The 1997 Prelude is equipped with a theft deterrent feature called the immobilizer system. When the correct key is used in the ignition switch, atransponder inside the key sends an identification (ID) code to the immobilizer receiver. The receiver then sends the code to the immobilizer control unit,allowing the engine to start. If an incorrect key is used in the ignition switch, the engine's fuel delivery and starter circuits are disabled.

This bulletin gives you information on system components, adding or replacing keys, replacing components, and emergency starting procedures.Additional information on the immobilizer system is in section 23 of the 1997 Prelude Service Manual and in the PROformance 1997 PreludeTechnician's Information Guide.
WARRANTY CLAIM INFORMATION

None. This Service Bulletin is for information only.

Immobilizer System Components

The immobilizer system has five main components:
^ Engine control module (ECM)
^ Immobilizer control unit
^ Immobilizer receiver
^ Immobilizer indicator light
^ keys: 2 master keys (black grip), 1 valet key (gray grip), and 1 learning key (red grip)

Engine Control Module (ECM)

The ECM is on the floor of the passenger compartment. When it receives the correct signal from the immobilizer control unit, the ECM enables the fuelsupply system.

Immobilizer Control Unit

The immobilizer control unit is below the dashboard, on the left side of the steeling column. When the ignition switch is turned on, the control unit sendspower to the transponder through the immobilizer receiver. When the control unit receives the ID code from the transponder, it compares it with the onein its memory.

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If the codes match, the control unit sends an enable signal to the ECM and connects the starter circuit. If the codes do not match, the control unit disablesthe starter circuit, and does not send an enable signal to the ECM. The control unit can accept up to five keys (not including the learning key).

Immobilizer Receiver

The immobilizer receiver is in the bezel surrounding the ignition switch. It supplies power to the transponder inside the key using electromagneticinduction. There is no physical connection between the key and the receiver. Once the transponder is powered up, it sends its ID code to the receiver,which then sends the code to the immobilizer control unit.

Immobilizer Indicator Light

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The immobilizer indicator light is on the right side of the instrument panel. When you turn the ignition switch on with the correct master key or valet key,the light goes on for two seconds, then it goes off. When you remove the key from the ignition switch, the light blinks for five seconds, then it goes off.

If you insert an incorrect key into the ignition switch, the indicator light goes on for two seconds, then it blinks continuously. When you remove the key,the light goes off immediately.

Immobilizer System Keys

The car comes with two master keys (black grip), one valet key (gray grip), and one learning key (red grip). All keys have a transponder inside them thatoutputs an ID code used by the immobilizer control unit to start the car. Keys have no batteries or serviceable parts inside them.

The master key operates the ignition switch, the doors, the trunk, the trunk release handle, the rear seat trunk access, and the glove box, When the correctmaster key is used in the ignition switch, its transponder sends an ID code to the immobilizer control unit, allowing the engine to start.
The valet key works like the master key, except it does not open the trunk, the trunk release handle, the rear seat trunk access, or the glove box.

The learning key has a unique ID code that is matched to the car's immobilizer control unit. It allows you to recode or replace a key, but it will not startthe engine. If you try to start the engine with the learning key, it may disable the fuel supply system and the starter system. If this happens, you will needto do the procedure in ADDING OR REPLACING KEYS.

The learning key is given to the customer, sealed in its plastic case. The customer should be advised that the learning key is a tool for the dealer to usewhen adding or replacing keys; it cannot be used to start the engine. The customer should keep the learning key sealed in its case and stored in a safeplace.

Adding or Replacing Keys

Since the car comes with three keys, and the immobilizer control unit can accept up to five codes, two more keys can be added to the system. Whenadding or replacing keys, you need these items:
^ Master Key Blank: P/N 35113-SZ3-Q01, H/C 5202502 or Valet Key Blank: P/N 35114-SZ3-Q01, H/C 5202510
^ Learning Key
^

All existing master keys and valet keys for the car (They need to be programmed along with the new key. If you do not have at least one master keyor valet key, refer to page 3 for REPLACING COMPONENTS.)
^ PGM Tester with SN 701 (or higher) software on a 4 MB program card
^

Password code for the PGM Tester program card (If you do not know the password code, ask your Service Manager for it, or find it on theHONDANET 2000 VIN Status Inquiry display.)

Procedure

1. Cut the new key(s).

2. Gather up all the keys for the car. (The immobilizer control unit accepts up to five keys.)

3. Connect the PGM Tester, then turn the ignition switch ON (II) with the master key or valet key.

4. Go into the immobilizer menu. (Do not use the "Generic OBD II" mode.)

5. Select REWRITE on the tester screen to bring up the rewriting menu.

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6. From the rewriting menu, select IMMOBI (Immobilizer unit). Follow all screen prompts until you return to the rewriting menu.

7. From the rewriting menu, select ECM, and follow the screen prompts. (You will need the password code for this step.)

8.

Start the engine with all master keys and valet keys. If any of the keys do not start the engine, you will have to repeat steps 3 through 8 for all ofthe keys.

9. When you are finished, put the learning key back into its plastic case, and return it to the customer.

Replacing Components

Use the chart, along with the information on the right, to find which immobilizer system component(s) you need to replace. For component testing andreplacement, refer to section 23 of the Service Manual. You will also need a PGM Tester with SN 701 (or higher) software on a 4 MB program card andthe password code for the card. If the repair involves the immobilizer control unit, lost keys, or improper use of the learning key in the ignition switch,the customer should supply you with the learning key, any available master keys and valet keys, and key numbers.

:NOTE

If you replace the immobilizer control unit, the ECM, or any keys, the immobilizer system must relearn the transponder ID code for the keys. (SeeADDING OR REPLACING KEYS.)
* If you know how to re-key locks, use D and re-key the rest of the locks to match the new ignition key lock. If you do not know how to re-key locks,

and the customer does not mind needing more than one key for the car, you can still use D. But if the customer wants all the lock cylinders to matchand you do not know how to re-key locks, use E.
Depending on what is wrong (lost keys, damaged ignition switch, faulty ECM, etc.), you may need one or more of these parts:
A Master Key Blank,

P/N 35113-SZ3-Q01, H/C 5202502 and

Valet Key Blank,

P/N 35114-SZ3-Q01, H/C 5202510

B Immobilizer Unit Set, ** P/N 04809-S30-A01

H/C 5198866

(Includes master key blank, valet key blank, learning key blank, and immobilizer control unit.)

C

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Engine Control Module(Refer to the Parts catalog for the part number.)

D Steering Lock Assembly P/N 35100-S30-A01, H/C 5202452

(Includes contents of A and B, plus the immobilizer receiver, the receiver harness, the steering lock, the steering lock wire harness, and the ignition key cylinder.)

E Key Cylinder Set

(Includes contents of 0, plus the lock cylinders for the doors, the glove box, the trunk, the trunk release handle, and the rear seat trunk access. (Refer

**After you replace the immobilizer control unit, program the keys that come with it using the procedure, ADDING OR REPLACING KEYS. Forprogramming, you must use the learning key that comes with the new control unit. (Keep the old learning key with the old control unit, for warrantypurposes).

When the PGM Tester refers to "original" keys, it means the keys that come with the new control unit. The keys used with the old control unit are now"new" keys that must be relearned by the new control unit.

Emergency Starting Procedures

If all of the keys are lost, you can still get the engine started in either of two ways: without the PGM Tester or with the PGM Tester. These proceduresare only a temporary repair; for a permanent repair, you may need to replace some or all of the immobilizer system components as described inREPLACING COMPONENTS.

Starting Engine Without PGM Tester

To start the engine without the PGM Tester, you need these items:
^ Regular key blank, P/N 35117-SM4-901, H/C 4225462, or equivalent
^ The five-digit immobilizer brake code from the HONDANET 2000 VIN Status Inquiry display. (The code is VIN-specific.)

:NOTE

^ After the engine is started with this procedure, you must repeat the procedure if the engine is turned off for more than ten minutes.
^ While the engine is running, the immobilizer indicator light on the instrument panel remains on.
^ Use this procedure only if the customer plans to drive the car directly to a Honda dealership for repair.

1. Cut a temporary key using a regular key blank.

2. Find the car's five-digit immobilizer brake code using the HONDANET 2000 VIN Status Inquiry display.

3. Turn the ignition switch ON (II) with the temporary key.

4.

Enter the first digit of the code by setting and releasing the parking brake lever the same number of times as the first digit. For example, if the firstdigit is 3, set and release the lever three times. (This step can be done faster if you press and hold the parking brake release button while you setand release the lever.)

: NOTE

While entering the code, the brake system indicator light stays on even when you release the parking brake lever.

5. Turn off the ignition switch. This enters the code into the immobilizer control unit.

6. Repeat steps 3, 4, and 5 using the second, third, fourth, and fifth digits of the code. You need to enter each digit of the code within thirty seconds.

7.

After you enter the fifth digit and turn off the ignition, the immobilizer indicator light will flash five times, then go off. This means the engine cannow be started with the new key that you made in step 1.

Starting Engine With PGM Tester

To start the engine with the PGM Tester, you need these items:
^ Regular key blank, P/N 3511 7-5M4-901, H/C 4225462, or equivalent
^ The four-digit ECM code (The code is VIN-specific.)
^ PGM Tester with SN 701 or later software on a 4 MB program card
^ Immobilizer jumper connector, T/N 07TAZ-SZ3010A
^

key tag, T/N 07TAZ-SZ3020A"IMPORTANT REMINDER"

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: NOTE

This procedure disables the immobilizer system, allowing the car to start 50 times. While the system is disabled, the immobilizer indicator light willremain on.

1. Cut a temporary key using a regular key blank.

2.

Find the car's four-digit ECM code using the HONDANET 2000 VIN Status Inquiry display. (The ECM code is called the IMMOBI DISABLECODE on the display.)

3. Connect the PGM Tester, then turn the ignition switch ON (11) with the temporary key, and go into the immobilizer menu.

4. From the immobilizer menu, select
CANCELLATION to bring up the cancellation menu.

5. From the cancellation menu, select CANCELLATION.

6. Enter the four-digit ECM code.

7.

Follow the screen prompts on the PGM Tester. When you successfully disable the immobilizer system, the last screen indicates "Immobilizer hasbeen cancelled."

8.

Disconnect the 8P wire harness connector from the immobilizer control unit, and plug the immobilizer jumper connector into it. (The engine willnot crank without the jumper connector.)

9.

"IMPORTANT REMINDER

Attach an key tag to the temporary key. This alerts the customer that the car must be repaired soon; the engine willstart only 50 times with the temporary key.

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Security Control Unit: Locations

Above Accelerator Pedal (Dealer Installed Option)

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Security Control Unit: DiagramsSecurity Control Unit

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Antitheft Relay: Locations

Left Side Of Dash (Dealer Installed Option)

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General Module: Diagram Information and Instructions

Circuit Schematics

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Each schematic represents one circuit. A circuit's wires and components are arranged to show current flow, from power at the top of the image, toground, at the bottom.

Shared Circuits

Other circuits may share power or ground terminals or wiring with the circuit shown. A wire that connects one circuit to another, for example, iscut short and has an arrowhead at the end of it pointing in the direction of current flow. Next to the arrowhead is the name of the circuit orcomponent which shares that wiring. To quickly check shared wiring, check the operation of a component it serves. If that component works, youknow the shared wiring is OK.

Connectors

All in-line and fuse box connectors are numbered (C725, C416, etc.). Component connectors are not numbered but are identified by the name ofthe component if the component only has one connector, or by a capital letter (A, B, C, etc.) if the component has more than one connector. Belowmost connector numbers and component names are PHOTO and VIEW numbers. The PHOTO number refers to a photo in the image that showsthe connector's location on the car. The VIEW number refers to an illustration in the image that shows the connector face, wire colors, connector

cavity numbers and other details. The connector cavity numbering sequence begins at the top left corner of the connector as seen from either of theviewpoints. Disregard any numbers molded into the connector housing.

Wires

Wires are identified by the abbreviated names of their colors; the second color is the color of the stripe. Wires are also identified by their locationin a connector. The number "2" next to the male and female wire terminals at C416, for example, means those terminals join in cavity 2 ofconnector C416.

A complete description of schematic symbols is given under wire color abbreviation.Symbols

Component Locations

To see where a component or connector is located on the car, look up its photo number in the component location section. The photo will also tell youthe color of the connector, and how many cavities it has.

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If there is no photo number below or beside a component name or a connector, ground or terminal number, look up that name or number in appropriateconnector identification chart. The chart lists how many cavities a connector has, where it's located, and what it connects to. The related illustrationshows the connector's location on the harness & the harness routing.

Ground Distribution Schematics

This sample Ground Distribution schematic shows all of the components that share two ground points.

Inline Connector Circuit Identification

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To see the configuration of a connector's cavities, look up its view number in the connector view section. Each view includes the color of the connector,where it is located and what it connects to.

Use the connector views to help to locate the proper cavity when you need to probe a connector. It can be especially helpful if the connector has morethan one wire of the same color.

Connector views can also be used to help diagnose multiple symptoms in separate circuits which could be caused by a single problem in a connectorshared by those circuits. Here's how:

1. Pick one of the multiple symptoms and look up the schematic for that circuit.2. Make a list of all in-line and fuse box connectors in that schematic.3. Then, in this connector view section, look up each connector on your list to see if circuits related to the other symptoms run through one of them.
If they do, inspect that connector for the problem.

Example:

The blower, rear window defogger, and the windshield wiper, don't work. List all in-line and fuse box connectors in the blower control circuitand then check the connector view section. You find that C324 is common to the rear window defogger circuit and wiper/washer circuit, so you inspectC324 and find the problem, bent terminals.

Power Distribution Schematics

Power Distribution schematics show how power is supplied from the positive battery terminal to various circuits in the car. Refer to the PowerDistribution section to get a more detailed picture of how power is supplied to the circuit you're working on.

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From Battery to Ignition Switch, Fuses and Relays

Individual circuit schematics begin with a fuse. The first half of Power Distribution, however, shows the wiring "upstream" between the batteryand the fuses.

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From Fuses to Relays and Components

The second half of Power Distribution shows the wiring "From Fuses to Relays and Components." This can speed your troubleshooting byshowing which circuits share fuses. If Power Distribution shows that an inoperative circuit and another circuit share a fuse, check a component inthe other circuit. If it works, you know the fuse is good and power is available to the inoperative circuit.

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Wire Color Abbreviations

The following abbreviations are used to identify wire colors in the circuit schematics:BLK ............................................................................................................................................................................................................................ blackBLU .............................................................................................................................................................................................................................. blueBRN .......................................................................................................................................................................................................................... brownGRN ........................................................................................................................................................................................................................... greenGRY ............................................................................................................................................................................................................................. grayLT BLU ................................................................................................................................................................................................................ light blueLT GRN ............................................................................................................................................................................................................. light greenORN ......................................................................................................................................................................................................................... orangePNK ............................................................................................................................................................................................................................. pinkPUR ........................................................................................................................................................................................................................... purpleRED ............................................................................................................................................................................................................................... redWHT ........................................................................................................................................................................................................................... whiteYEL .......................................................................................................................................................................................................................... yellow

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Wire Color Codes

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The following abbreviations are used to identify wire colors in the circuit schematics:

WHT White
YEL Yellow
BLK Black
BLU Blue
GRN Green
RED Red
ORN Orange
PNK Pink
BRN Brown
GRY Gray
PUR Purple

LT BLU Light BlueLT GRN Light Green

The wire insulation has one color or one color with another color stripe. The second color is the stripe.

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General Module: Diagnostic Aids

Five Step Troubleshooting

1. Verify The Complaint

Turn on all the components in the problem circuit to check the accuracy of the customer complaint. Note the symptoms. Do not begin disassemblyor testing until you have narrowed down the problem area.

2. Analyze The Schematic

Look up the schematic for the problem circuit. Determine how the circuit is supposed to work by tracing the current paths from the power sourcethrough the circuit components to ground. Also, trace circuits that share wiring with the problem circuit. The names of circuits that share the samefuse, ground, or switch, and so on, are referred to in each circuit schematic. Try to operate any shared circuits you didn't check in step 1. If theshared circuits work, the shared wiring is OK, and the cause must be in the wiring used only by the problem circuit. If several circuits fail at thesame time, the fuse or ground is a likely cause.
Based on the symptoms and your understanding of the circuit's operation, identify one or more possible causes.

3. Isolate The Problem By Testing The Circuit

Make circuit tests to check the diagnosis you made in step 2. Keep in mind that a logical, simple procedure is the key to efficient troubleshooting.Test for the most likely cause of failure first. Try to make tests at points that are easily accessible.

4. Fix The Problem

Once the specific problem is identified, make the repair. Be sure to use proper tools and safe procedures.

5. Make Sure The Circuit Works

Turn on all components in the repaired circuit in all modes to make sure you've fixed the entire problem. If the problem was a blown fuse, be sureto test all of the circuits on that fuse. Make sure no new problems turn up and the original problem does not recur.

Troubleshooting Precautions
Before Troubleshooting

1. Check the main fuse and the fuse box.2. Check the battery for damage, state of charge, and clean and tight connections.

CAUTION:

^ Do not quick-charge a battery unless the battery ground cable has been disconnected, or you will damage the alternator diodes.
^ Do not attempt to crank the engine with the ground cable disconnected or you will severely damage the wiring.

While You're Working

08798-9001

1. Make sure connectors are clean, and have no loose terminals or receptacles.2. Make sure multiple terminal connectors are packed with dielectric (silicone) grease. Part Number: .3. When connecting a connector, push it until it clicks into place.

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CAUTION:

^ Do not pull on the wires when disconnecting a connector. Pull only on the connector housings.
^

10-mega Ohm

Most circuits include solid-state devices. Test the voltages in these circuits only with a or higher impedance digital multimeter.Never use a test light or analog meter on circuits that contain solid-state devices. Damage to the devices may result.

Short to Ground With Self-Powered Test Light or DVOM

1. Remove the blown fuse and disconnect the battery and load.2. Connect one lead of a self-powered test light or (switched to the lowest "OHMS" range) to the fuse terminal onDigital Volt/Ohmmeter (DVOM)

the load side.

six inches

3. Connect the other lead to a known good ground.4. Beginning near the fuse box, wiggle the harness. Continue this at convenient points about apart while watching the test light or DVOM.5. If the self-powered test light goes on or the DVOM displays a low reading or no reading (ZERO), there is a short to ground in the wiring near that
point.

Testing For A Short to Ground With A Test Light or DVOM

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1. Remove the blown fuse and disconnect the load.2. Connect a test light or , switched to the appropriate DC Volts range, across the fuse terminals to make sureDigital Volt/Ohmmeter (DVOM)

voltage is present. You might have to turn the ignition switch to ; check the schematic to see.ON

six inches

3. Beginning near the fuse box, wiggle the harness. Continue this at convenient points about apart while watching the test light or DVOM.4. Where the test light goes , or the DVOM voltage drops to , there is a short to ground in the wiring near that point.OFF ZERO
Always use a DVOM on high impedance circuits. A test light may not glow (even with battery voltage present).NOTE:

Testing For a Short With a Short Circuit Locator (Short Finder)

1. Remove the blown fuse. Leave the battery connected.2. Connect the short finder across the battery terminals and the load (component) side of the fuse terminal.3. Close all switches in the circuit you're testing.4. Turn on the short finder. This creates a pulsing magnetic field around the wiring between the fuse box and the short.5. Beginning at the fuse box, slowly move the short finder along the circuit wiring. The meter will show current pulses through sheet metal and body
trim. As long as the meter is between the fuse and the short, the needle will move with each current pulse. Once you move the meter past the pointof the short, the needle will stop moving. Check the wiring and connectors in this area to locate the cause of the short.

Testing For Continuity

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When testing for continuity at a connector without wire seals, you do not have to separate the two halves of the connector. Instead, probe the connectorfrom the back. Always check both sides of the connector because dirty, corroded, and bent terminals can cause problems (no electrical contact = anopen).

Digital Volt/Ohmmeter (DVOM) "OHMS"

1. Disconnect the negative cable from the car battery. If you're using a , place it in the lowest range.2. Connect one lead of a self-powered test light or DVOM to one end of the part of the circuit you want to test.3. Connect the other lead to the other end.4. If the self-powered test light glows, there is continuity. If you're using a DVOM, a low reading or no reading (ZERO), means good continuity.

Testing For Voltage

When testing for voltage at a connector without wire seals, you do not have to separate the two halves of the connector. Instead, probe the connectorfrom the back. Always check both sides of the connector because dirty, corroded, and bent terminals can cause problems (no electrical contact = anopen).

1. Connect one lead of the test light to a known good ground, or, if you're using a , place it in the appropriate DCDigital Volt Ohmmeter (DVOM)

Volts range, and connect its negative lead to ground.

voltage.A loss of more than indicates a problem.one Volt

Always use a DVOM on high impedance circuits. A test light may not glow (even with battery voltage present).NOTE:

Testing For Voltage Drop

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Prelude Type-SH L4-2156cc 2.2L DOHC (VTEC) MFI (1997)

2. Connect the other lead of the test light or DVOM to the point you want to check.3. If the test light glows, there is voltage present. If you're using a DVOM, note the voltage reading. It should be within of measured batteryone Volt

one Volt

Wires, connectors, and switches are designed to conduct current with a minimum loss of voltage. A voltage drop of more than indicates aproblem.

1. Place the in the appropriate DC Volts range. Connect the positive lead to the end of the wire (or to theDigital Volt/Ohmmeter (DVOM)

connector or switch) closest to the battery.

2. Connect the negative lead to the other end of the wire (or the other side of the connector or switch).3. Turn on the components in the circuit.4. The DVOM will show the difference in voltage between the two points. A difference, or drop, of more than indicates a problem. Checkone Volt

the circuit for loose, dirty, or bent terminals.

> Relays and Modules > Relays and Modules - Accessories and Optional Equipment > General Module > Component Information > Diagrams > Diagram Information and Instructions > Page 41

> Relays and Modules > Relays and Modules - Accessories and Optional Equipment > General Module > Component Information > Description and Operation > Description

General Module: Description and OperationDescription

The multiplex control unit is composed of three control units (located in the driver's side kick panel, passenger's side kick panel, and driver's door).These three control units integrate the independent control units as usual and feature multiplex communication lines. The system reduces the number ofcontrol units and wire harness bulk, and improves the quality of electrical functions by means of the integrated circuits. This system has a built-inself-diagnosis function.

> Relays and Modules > Relays and Modules - Accessories and Optional Equipment > General Module > Component Information > Description and Operation > Description > Page 44

General Module: Description and OperationSystem Functions

^

Multiplex Control System-

Multiplex function

- Wake up/sleep function

- Fail-safe function

-

Self-diagnosis functionMode 1: Self-diagnosis for the multiplex control system.Mode 2: Failure diagnosis for the input line of each system.

^

Integrated Control System-

Seat Belt Reminder Circuit

- Lights-on Reminder Circuit

- Key-in Reminder Circuit

- Engine Oil Pressure Indicator Flasher Circuit

^ Dash Lights Brightness Control
^ Entry Light Control System
^ Power Door Locks
^ Power Window
^ Wiper/Washer
^ Interlock System
^ Rear Window Defogger

MULTIPLEX COMMUNICATION SYSTEM

^Multiplex Communication Functions

To reduce the number of wire harnesses, digital signals are sent via shared multiplex communication lines rather than sending normal electricalsignals through individual wires.

^

The input signals from each switch are converted to digital signals at the central processing unit (CPU). The digital signals are sent from thetransmitter unit to the receiver unit as serial signals.
^ The transmitted signal is converted to a switch signal at the receiver unit, and it operates the related component.
^

There are exclusive communication lines between each of the multiplex control units:-

Door -> Driver's (from the door to the driver's multiplex control units) Wire color: BRN

- Driver's -> Passenger's (from the driver's to the passenger's multiplex control units) Wire color: LT GRN

- Passenger's -> Driver's (from the passenger's to the driver's multiplex control units) Wire color: PNK

^ The control units always communicate via these lines when the system is operating, and they stop communicating when the system is OFF.

^Wake-up and Sleep Functions

The multiplex control system has "wake-up" and "sleep" functions to decrease parasitic draw on the battery when the ignition switch is OFF.

^

In the sleep mode, the multiplex control unit stops the functions (communication and CPU control) when it is not necessary for the system tooperate.
^

As soon as any operation is done (for example, a door is unlocked), the related control unit in the sleep mode wakes up and begins to functionat once. This control unit also sends a wake-up signal to the other control units via the communication lines.
^

OFF 10 second

When the ignition switch is turned , there is about a delay before the control units go from the wake-up mode to the sleepmode.
^ If any door is open, the sleep mode will not function.

^Fail-safe Functions

To prevent improper operation, the multiplex control system has a fail-safe function. In the fail-safe mode, the output signal is fixed when anypart of the system malfunctions (for example, a faulty control unit or communication line).

^

Each control unit has a hardware fail-safe function that fixes the output signal when there is any CPU malfunction and a software fail-safefunction that ignores the signal from the malfunctioning control unit and allows the system to operate normally.

> Relays and Modules > Relays and Modules - Accessories and Optional Equipment > General Module > Component Information > Testing and Inspection > Symptom Related Diagnostic Procedures

General Module: Symptom Related Diagnostic Procedures

Faulty Communication Line Symptoms
Open in the line:

If the is an open in a communication line, most of the systems do not operate because one of the control units cannot wake up the other control units.But the control unit that is not awake can wake up by operating a switch related to the control unit.All of the control units wake up by turning the ignition switch (II).ON

Short in the line:

^ Most of the systems do not operate because one of the control units cannot wake up the other control units.^ The control unit can wake up by a related switch operation, but the other control units cannot wake up.^ All of the control units wake up by turning the ignition switch (II).ON

> Relays and Modules > Relays and Modules - Accessories and Optional Equipment > General Module > Component Information > Testing and Inspection > Symptom Related Diagnostic Procedures > Page 47

General Module: Component Tests and General Diagnostics

Confirming The Function

1. Shifting to the sleep mode:

OFF

1. Turn the ignition switch .2. Cancel the key-off operation timer in the power window system by opening and closing one of the doors.3. Make sure that the exterior lights are off.4. If you do not operate the switches related to the multiplex control units more than after meeting the above conditions, the systemone minute

function shifts to the sleep mode.(All of the switches must be turned except door lock knob switches.)OFF

2. Confirming the sleep mode:

1. Check for voltage between the communication line.

There should be no voltage with the sleep mode ON.There should be standard voltage with the sleep mode OFF (see the voltage test table).

2. Check for voltage between each communication line and body ground while shifting to the sleep mode.

There should be no voltage.

3. Check the parasitic draw at the battery while shifting to the sleep mode. The ampere should change from about through to less than 70 80 mA
.10 mA

3. Confirming the wake up mode:

After confirming the sleep mode, turn the related switch ON, and wake up each control unit. If all of the operations works properly, the wake upmode is OK.(If any of the control units are faulty and cannot wake up, several parts of the system will not work at the same time.)

Multiplex Control System
Multiplex Control Unit (Door):

1. Remove the driver's door panel, and disconnect the 2OP connector from the door unit.

> Relays and Modules > Relays and Modules - Accessories and Optional Equipment > General Module > Component Information > Testing and Inspection > Symptom

Related Diagnostic Procedures > Page 48

Prelude Type-SH L4-2156cc 2.2L DOHC (VTEC) MFI (1997)

2. Inspect the connector and socket terminals to be sure they are all making good contact.
^ If the terminals are bent, loose or corroded, repair them as necessary, and recheck the system.
^

If the terminals look OK, make the following input tests at the connector.-

If a test indicates a problem, find and correct the cause, then recheck the system.

- If all the input tests prove OK, the control unit (power window master switch) must be faulty; replace it.

Multiplex Control Unit (Passenger's):

1. Remove the right kick panel.2. Disconnect the 14P and 20P connectors, then remove the passenger's unit.

> Relays and Modules > Relays and Modules - Accessories and Optional Equipment > General Module > Component Information > Testing and Inspection > Symptom

Related Diagnostic Procedures > Page 49

Prelude Type-SH L4-2156cc 2.2L DOHC (VTEC) MFI (1997)

3. Inspect the connector and socket terminals to be sure they are all making good contact.
^ If the terminals are bent, loose or corroded, repair them as necessary, and recheck the system.
^

If the terminals look OK, make the following input tests at the connector.-

If a test indicates a problem, find and correct the cause, then recheck the system.

- If all the input tests prove OK, the control unit must be faulty; replace it.

Multiplex Control Unit (Driver's):

1. Remove the under-dash fuse/relay box.2. Remove the driver's unit from the under-dash fuse/relay box.

> Relays and Modules > Relays and Modules - Accessories and Optional Equipment > General Module > Component Information > Testing and Inspection > Symptom

Related Diagnostic Procedures > Page 50

Prelude Type-SH L4-2156cc 2.2L DOHC (VTEC) MFI (1997)

3. Inspect the connector and socket terminals to be sure they are all making good contact.
^ If the terminals are bent, loose or corroded, repair them as necessary, and recheck the system.
^

If the terminals look OK, make the following input tests at the connector and the fuse/relay box socket.-

If any test indicates a problem, find and correct the cause, then recheck the system.

- If all the input tests prove OK, the control unit must be faulty; replace it.

Self-Diagnosis Function (Mode 1)

> Relays and Modules > Relays and Modules - Accessories and Optional Equipment > General Module > Component Information > Testing and Inspection > Symptom

Related Diagnostic Procedures > Page 51

Prelude Type-SH L4-2156cc 2.2L DOHC (VTEC) MFI (1997)

^

One second

after you go into self-diagnosis function mode 1, the function starts to indicate the diagnostic trouble code (DTC), and repeats theDTC every .three seconds

^

five ten seconds

From mode 1, disconnect the SCS service connector for to , then reconnect the SCS service connector, and the function goes frommode 1 to mode 2.

^ Make sure the ceiling light switch is in the middle position.

NOTE:

If no DTCs are indicated, but you know the system is abnormal, check these items:^

^ If only the lights or the buzzer indicates the DTC(s), the lights or buzzer is probably faulty.

Diagnostic Trouble Code (DTC) Table

The numbers in the table show the troubleshooting sequence.NOTE:

> Relays and Modules > Relays and Modules - Accessories and Optional Equipment > General Module > Component Information > Testing and Inspection > Symptom

Related Diagnostic Procedures > Page 52

Prelude Type-SH L4-2156cc 2.2L DOHC (VTEC) MFI (1997)

If the lights do not come on and buzzer does not beep, check the continuity between the BLK wire of the multiplex control inspection connectorand body ground, and check the continuity between the LT BLU wire of the multiplex control inspection connector and multiplex control unit(driver's).

Communication Line Test

1. Continuity Test
Check for continuity according to the table.^

If there is continuity, go to step 2.

^ If there is no continuity, check for an open in the wire.

2. Voltage Test

A. Turn the ignition switch (II).ON

B. Check for voltage between communication line and ground:

The voltage should match the table in the image.

^

If the voltage is too high:A. Check for short to another wire.B. Check for poor contact at the connector on the receiver side unit.C. Faulty circuit in the receiver side unit.

^

If the voltage is too low:A. Check for short to ground or to another wire.B. Check for poor contact at the connector on the transmit side unit.C. Faulty circuit in the transmitter side unit.

If any control unit appears to be faulty, select one control unit, substitute a known-good control unit, then recheck. If the system works properly, theoriginal control unit is faulty; replace it. If there is still a malfunction, substitute a known-good control unit for another control unit, then recheck. If thesystem works properly, that control unit is faulty; replace it.

Self-Diagnosis Function (Mode 2)

1. Operate the switches as shown in mode 2.2. If the related circuit line of the switch is OK, the function indicates this by the ignition key light and ceiling light blinking once and the beeper
sounding once.

> Relays and Modules > Relays and Modules - Accessories and Optional Equipment > General Module > Component Information > Testing and Inspection > Symptom

Related Diagnostic Procedures > Page 53

Prelude Type-SH L4-2156cc 2.2L DOHC (VTEC) MFI (1997)

five ten seconds

10 seconds

From mode 1, disconnect the SCS service connector from the multiplex control inspection connector for to , then reconnect the SCSservice connector again, and the function goes from mode 1 to mode 2.To cancel mode 2, disconnect the SCS service connector from the multiplex control inspection connector for more than or turn the ignitionswitch .OFF

If the line is faulty, there should be no indication. Refer to the tests for each system.NOTE:

Wake-Up Function Test
Description:

^

ON
ON

When the ignition switch is turned (II):When the ignition switch is (II), all of the multiplex control units wake up at the same time. In this case, the communication lines are notrelated for wake up function.

^

When a switch related to the multiplex control unit (door) is operated:First, the multiplex control unit (door) wakes up, then the control unit starts to communicate to the control unit (driver's). By this communication,the control unit (driver's) wakes up. The control unit (driver's) wakes the control unit (passenger's) up by the communication line, and all thecontrol units start to function.

^ When a switch related to the multiplex control unit (driver's or passenger's) is operated:

The control unit related to the operated switch wakes up, then the control unit wakes up the other unit. (In this case, the control unit (door) doesnot wake up.)

Related Switch (Input):

The switches and input signals that can wake up the multiplex control unit are shown:

Related Switch (Input) Table:

> Relays and Modules > Relays and Modules - Accessories and Optional Equipment > Keyless Entry Module > Component Information > Diagrams

> Relays and Modules > Relays and Modules - Accessories and Optional Equipment > Keyless Entry Module > Component Information > Diagrams > Page 57

Keyless Entry Module: Testing and Inspection

1. Remove the rear seat.2. Remove the left quarter trim panel.3. Disconnect the 8P connector from the keyless receiver unit.

4. Inspect the connector and socket terminals to be sure they are all making good contact.
^ If the terminals are bent, loose or corroded, repair them as necessary, and recheck the system.

^

If the terminals look OK, make the following input tests at the connector.-

If any test indicates a problem, find and correct the cause, then recheck the system.

- If all the input tests prove OK, the control unit must be faulty; replace it.

> Relays and Modules > Relays and Modules - Body and Frame > Door Lock Relay > Component Information > Diagrams

> Relays and Modules > Relays and Modules - Body and Frame > Door Lock Relay > Component Information > Diagrams > Page 62

Door Lock Relay: Testing and Inspection
Five-terminal type A:

1. Check for continuity between the terminals.
^ There should be continuity between the No.1 and No.2 terminals when power and ground are connected to the No.3 and No.5 terminals.
^ There should be continuity between the No.1 and No.4 terminals when power is disconnected.

^ Door lock relay

> Relays and Modules > Relays and Modules - Body and Frame > Keyless Entry Module > Component Information > Diagrams

> Relays and Modules > Relays and Modules - Body and Frame > Keyless Entry Module > Component Information > Diagrams > Page 66

Keyless Entry Module: Testing and Inspection

1. Remove the rear seat.2. Remove the left quarter trim panel.3. Disconnect the 8P connector from the keyless receiver unit.

4. Inspect the connector and socket terminals to be sure they are all making good contact.
^ If the terminals are bent, loose or corroded, repair them as necessary, and recheck the system.

^

If the terminals look OK, make the following input tests at the connector.-

If any test indicates a problem, find and correct the cause, then recheck the system.

- If all the input tests prove OK, the control unit must be faulty; replace it.

> Relays and Modules > Relays and Modules - Body and Frame > Power Door Lock Relay > Component Information > Locations

Power Door Lock Relay: Locations

Left Side Of Dash (Dealer Installed Option)

> Relays and Modules > Relays and Modules - Body and Frame > Power Door Lock Relay > Component Information > Locations > Page 70

Driver's Only Unlock Relay

> Relays and Modules > Relays and Modules - Body and Frame > Seat Heater Relay > Component Information > Locations

> Relays and Modules > Relays and Modules - Body and Frame > Seat Heater Relay > Component Information > Locations > Page 74

Seat Heater Relay: Testing and Inspection
Normally open type A:

1. Check for continuity between the terminals.
^ There should be continuity between the No. 1 and No.2 terminals when power and ground are connected to the No.3 and No.4 terminals.
^ There should be no continuity between the No.1 and No.2 terminals when power is disconnected.

^ Seat heater relay

Type 1:

Type 2:

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