CAT 3126E SCHEMATIC

SCHEMATIC FEATURES AND TIPS

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Vol 1 - Cab Wiring

032 (Red) (Battery Power)

640 (Blue) (Key Power)

021 (Orange) (Starting)

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640 (Blue) (Key Power) CIRCUIT ISOLATED

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CORNER OF EVERY MACHINE VIEW PAGE.

CLICK HERE TO VIEW THE SCHEMATIC

SYMBOLS AND DEFINITIONS PAGE

ELECTRICAL SYMBOLS

Pressure

Switch

T

Temperature

Switch

Level

Switch

Circuit Breaker

BASIC HYDRAULIC SYMBOLS

Fluid

Conditioner

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Pump

or Motor

HOTKEYS (Keyboard Shortcuts)

FUNCTION

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Fit to Page

Hand Tool

Find

Search

Spring

(Adjustable)

“CTRL” / “+”

“CTRL” / “-”

“CTRL” / “0” (zero)

“SPACEBAR” (hold down)

“CTRL” / “F”

“CTRL” / “SHIFT” / “F”

Variability

KEYS

© 2022 Caterpillar. All Rights Reserved. CAT, CATERPILLAR, LET’S DO THE
WORK, their respective logos, “Caterpillar Corporate Yellow”, the “Power Edge”
and Cat “Modern Hex” trade dress as well as corporate and product identity used
herein, are trademarks of Caterpillar and may not be used without permission.

SCHEMATIC SYMBOLS AND DEFINITIONS

One Position

Two-way

A B

P T

Normal Position

Basic

Symbol

VALVES

ENVELOPES

Two Position

PORTS

Three-Way

CONTROL

A B

P T

Shifted Position

CHECK

Spring

Loaded

Shuttle

Three Position

Four-Way

Infinite Position

Pilot

Controlled

PILOT CONTROL

RELEASED PRESSURE

INTERNAL PASSAGEWAYS

FLOW IN ONE

DIRECTION

Infinite

Positioning

FLOW ALLOWED IN
EITHER DIRECTION

Two

Position

CYLINDERS

Single Acting

Double Acting

ACCUMULATORS

Spring Loaded

Gas Charged

PARALLEL

FLOW

Three

Position

CROSS

FLOW

PUMPS

FIXED DISPLACEMENT

Unidirectional

Bidirectional

VARIABLE DISPLACEMENT

NON- COMPENSATED

Unidirectional

Bidirectional

MOTORS

FIXED DISPLACEMENT

Unidirectional

Bidirectional

VARIABLE DISPLACEMENT

NON- COMPENSATED

Unidirectional

Bidirectional

ROTATING SHAFTS

BASIC HYDRAULIC

COMPONENT SYMBOLS

Pump

or Motor

Fluid

Conditioner

Spring

Control

Valves

Restriction

Line Restriction

Variable and Pressure

Compensated

Variability

Spring

(Adjustable)

Pressure

Compensation

Line Restriction

(Variable)

Line Restriction

(Fixed)

AUX.

MAIN

2-Section

Pump

External Return

Simplified

Solenoid

Push-pull Lever PedalGeneral Manual Push Button SpringManual Shutoff

Solenoid

or Manual

Solenoid
and Pilot

HYDRAULIC SYMBOLS - ELECTRICAL

Internal Return

REMOTE SUPPLY PRESSURE

Complete

Internal

Supply Pressure

COMBINATION CONTROLS

Solenoid and

Pilot or Manual

Servo

MANUAL CONTROL

Thermal

Detent

Unidirectional

Bidirectional

Pump: Variable and

Pressure Compensated

MEASUREMENT

Temperature

Flow

Crossing

LINES

Joining

Attachment

Hydraulic Pneumatic

Energy Triangles

Pressure

FLUID STORAGE RESERVOIRS

Vented Pressurized Return Above Fluid Level Return Below Fluid Level

ELECTRICAL SYMBOLS

Transducer

(Fluid)

T

Transducer

(Gas / Air)

G

Generator

M

Electric

Motor

Pressure

Switch

Pressure Switch

(Adjustable)

Temperature

Switch

Electrical

Wire

BASIC ELECTRICAL COMPONENT SYMBOLS

Fuse: A component in an electrical circuit that will open the circuit if too much current flows through it.

Switch (Normally Open): A switch that will close at a specified point (temp, press, etc.). The circle indicates

Switch (Normally Closed): A switch that will open at a specified point (temp, press, etc.).

Ground (Wired): This indicates that the component is connected to a grounded wire.

The grounded wire is fastened to the machine.

Ground (Case): This indicates that the component does not haveawire connected to ground.

It is grounded by being fastened to the machine.

Reed Switch: A switch whose contacts are controlled by a magnet. A magnet closes the contacts of

a normally open reed switch; it opens the contacts of a normally closed reed switch.

Sender: A component that is used with a temperature or pressure gauge.

The sender measures the temperature or pressure.
Its resistance changes to give an indication to the gauge of the temperature or pressure.

Relay (Magnetic Switch): A relay is an electrical component that is activated by electricity.

Solenoid: A solenoid is an electrical component that is activated by electricity.

It has a coil that makes an electromagnet when current flows through it.
The electromagnet can open or close a valve or move a piece of metal that can do work.

Magnetic Latch Solenoid: An electrical component that is activated by electricity and held latched by a

that the component has screw terminals and a wire can be disconnected from it.

No circle indicates that the wire cannot be disconnected from the component.

It has a coil that makes an electromagnet when current flows through it.
The electromagnet can open or close the switch part of the relay.

permanent magnet. It has two coils (latch and unlatch) that make electromagnet
when current flows through them. It also has an internal switch that places
the latch coil circuit open at the time the coil latches.

Pressure

Switch

T

Temperature

Switch

Switch

HARNESS AND WIRE SYMBOLS

Wire, Cable, or Harness Assembly Identification:

Includes Harness Identification Letters and Harness
Connector Serialization Codes (see sample).

AG-C4

Part Number: for
Connector Plug

Harness Identification Letter(s): (A, B, C, AA, AB, AC, ...)
Harness Connector Serialization Code: The "C" stands for

"Connector" and the number indicates which connector in the
harness (C1, C2, C3, ...)

L-C12
3E-5179

Fuse (5 Amps)

Harness identification code:

This example indicates wire group 325,

wire 135 in harness "AG".

1
2

1
2

111-7898

Plug

5A

*Wire gauge is shown in AWG (American Wire Gauge)
but could also be shown in metric denoted with mm

Deutsch connector: Typical representation
of a Deutsch connector. The plug contains all
sockets and the recept

Sure-Seal connector: Typical representation
of a Sure-Seal connector. The plug and receptacle
contain both pins and sockets.

Level

Flow

Switch

L-C12
3E-5179

1

2

9X-1123

325-AG135 PK-14

acle contains all pins.

Circuit Breaker

Receptacle
Pin or Socket Number

Component
Part Number

Wire Gauge*
Wire Color

© 2022 Caterpillar. All Rights Reserved. CAT, CATERPILLAR, LET’S DO THE
WORK, their respective logos, “Caterpillar Corporate Yellow”, the “Power Edge”
and Cat “Modern Hex” trade dress as well as corporate and product identity used
herein, are trademarks of Caterpillar and may not be used without permission.

RENR1368-06

April 2022

3126B and 3126E Off-Highway Engine
Electrical System

3126B:
BKD1-UP
1AJ1-UP
8YL1-UP
8SZ1-UP

3126E:
G3E1-UP
CKM1-UP
CRP1-UP
7AS1-UP
9SZ1-UP

PUBLICATIONS.CAT.COM

© 2022 Caterpillar. All Rights Reserved. CAT, CATERPILLAR, LET’S DO THE WORK, their respective logos, “Caterpillar Corporate Yellow”, the “Power Edge”
and Cat “Modern Hex” trade dress as well as corporate and product identity used herein, are trademarks of Caterpillar and may not be used without permission.

DIAGNOSTIC CODE LISTING

PID-FMI Description

00-00 No Detected Faults 55 0105-03 Intake Manifold Air Temperature voltage high 38

0001-11 Cylinder #1 Injector current fault 72 0105-04 Intake Manifold Air Temperature voltage low 38

0002-11 Cylinder #2 Injector current fault 72 0105-11 Very High Intake Manifold Air Temperature 64

0003-11 Cylinder #3 Injector current fault 73 0108-03 Barometric Pressure voltage high 26

0004-11 Cylinder #4 Injector current fault 73 0108-04 Barometric Pressure voltage low 26

0005-11 Cylinder #5 Injector current fault 74 0110-00 High Coolant Temperature Warning 61

0006-11 Cylinder #6 Injector current fault 74 0110-03 Coolant Temperature voltage high 27

0022-11 Primary to Secondary Engine Speed Signal Calibration 42 0110-04 Coolant Temperature voltage low 27

0022-13 Engine Speed Signal Calibration Not Performed 42 0110-11 Very High Coolant Temperature 61

0030-08 PTO Throttle signal invalid 29 0111-01 Low Coolant Level Warning 62

0030-13 PTO Throttle out of calibration 29 0111-02 Coolant Level signal invalid 12

0041-03 8 Volt Supply voltage high 21 0111-03 Coolant Level voltage high 12

0041-04 8 Volt Supply voltage low 21 0111-04 Coolant Level voltage low 12

0042-11 Injection Actuation Pressure output fault 0111-11 Very Low Coolant Level 62

0043-02 Key Switch Fault 71 0128-03 Secondary Fuel Level voltage high

0064-02 Secondary Engine Speed loss of signal 34 0128-04 Secondary Fuel Level voltage low

0064-11 Secondary Engine Speed no pattern 34 0164-00 Excessive Injection Actuation Pressure 17

0070-05 Inlet Air Heater current low 0164-02 Injection Actuation Pressure Signal Erratic 15

0070-06 Inlet Air Heater current high 0164-03 Injection Actuation Pressure voltage high 15

0071-00 Idle Shutdown Override 01 0164-04 Injection Actuation Pressure voltage low 15

0071-01 Idle Shutdown 47 0164-11 Injection Actuation Pressure system fault 39

0071-14 PTO Shutdown 47 0168-02 ECM Battery Power Intermittent 51

0084-00 Vehicle Overspeed Warning 41 0186-14 PTO Engine Shutdown Switch Occurrence 47

0084-01 Vehicle Speed loss of signal 31 0190-00 Engine Overspeed Warning 35

0084-02 Vehicle Speed signal invalid 36 0190-02 Primary Engine Speed Loss of Signal 34

0084-08 Vehicle Speed signal out of range 0190-11 Primary Engine Speed no pattern

0084-10 Vehicle Speed signal rate of change 36 0224-11 Theft Deterrent Active

0091-08 Throttle Position Invalid 32 0224-14 Theft Deterrent Active with Engine Cranking

0091-13 Throttle Position out of calibration 28 0231-02 J1939 Data Incorrect 58

0096-03 Fuel Level voltage high 0231-11 J1939 Data Link Fault 58

0096-04 Fuel Level voltage low 0231-12 J1939 Device Not Responding

0100-03 Oil Pressure voltage high 24 0232-03 5 Volt Supply voltage high 21

0100-04 Oil Pressure voltage low 24 0232-04 5 Volt Supply voltage low 21

0100-11 Very Low Oil Pressure 46 0246-11 Brake Pedal Switch #1 Fault

0102-03 Boost Pressure voltage high 25 0247-11 Brake Pedal Switch #2 Fault

0102-04 Boost Pressure voltage low 25 0252-11 Engine Software Incorrect 59

0102-07 Boost Pressure not responding 0253-02 Check Customer or System Parameters 56

0105-00 High Intake Manifold Air Temperature Warning 64 0253-14 Truck Manufacturer Parameter Not Programmed

Flash

Codes

PID-FMI Description

Flash

Codes

ECM CONNECTOR

ECM Connectors

ECM Side

ECM Side

ECM Connector P2

HarnesECM Connector P1

DT Connector Receptacle DT Connector Plug

Receptacle Wedge

Plug Wedge

s Side

Harness Side

6 HEUI Injectors

Injection Actuation Pressure Control Valve

(IAPCV)

Top Camshaft Speed/Timing Sensor

Bottom Camshaft Speed/Timing Sensor

Injection Actuation Pressure Sensor

Boost Pressure Sensor

Atmospheric Pressure Sensor

Engine
Control
Module

Caterpillar Installed

OEM Installed

Accelerator Pedal Position Sensor

Ignition Key Switch

Cruise Control On/Off &

Set/Resume Switches

Clutch and Service Brake Switches

Coolant Level Sensor

Check Engine Lamp

A/C High Pressure Switch

Cab Diagnostic Connector

- 12 V +

Batteries

Warning Lamp

Speedometer & Tachometer

45

35 55

25

65

15

5

0

85

MPH

15

20

10

75

5

30

RPM X 1000

Cooling Fan

25

Receptacle Wedge

Receptacle Wedge

HD Connector Receptacle

Pin Contact

Speed/Timing Sensor Connectors

150 Series Receptacle

Socket Contact

Plug Wedge

Plug Wedge

HD Connector Plug

Sealing Plug

IAPCV Connector

150 Series Plug

(Specific Ratings Only)

Oil Pressure Sensor

(Optional)

Oil Level Switch

(Optional)

Coolant Temperature Sensor

Intake Manifold Air Temperature Sensor

Intake Air Heater Relay

Intake Air Heater

Vehicle Speed
Sensor

PTO Accelerator
Position Sensor

Fast Idle Enabled Lamp

Or Wait To Start Lamp

Fast Idle Enable Switch

PTO Switch On Lamp

PTO On/Off & PTO

Set/Resume Switches

Transmission Neutral Switch

AT/MT/HT Transmission Relay

Exhaust Brake On/Off Switch

Exhaust Brake

Intake Air Heater Lamp

A

RELATED ELECTRICAL SERVICE MANUALS

Title

Troubleshooting

Systems Operation / Testing and Adjusting

Form Number

RENR1367

RENR1271

67

3126B & 3126E ENGINE ELECTRICAL SCHEMATIC

INJECTOR HARNESS GROMMET

12345

F

E

D

L983-WH

J301 P301

B

F7 F6 F5 F4 F3 F2 F1

A

INJECTOR
CYLINDER
NO.1

ENGINE ATMOSPHERIC

ENGINE BOOST

PRESSURE

SENSOR

ENGINE INJECTION

ACTUATION

PRESSURE

SENSOR

PRESSURE

SENSOR

A701-GY

NOTE A

J302 P302

B
A

INJECTOR
CYLINDER
NO.2

E7

ENGINE OIL

PRESSURE

SENSOR

NOTE A

ENGINE OIL LEVEL

SWITCH

NOTE A

ENGINE COOLANT

TEMPERATURE

SENSOR

ENGINE INTAKE

MANIFOLD AIR

TEMPERATURE

SENSOR

D7

L983-WH

B
A

INJECTOR
CYLINDER
NO.3

A702-PU

ENGINE BOOST PRESSURE

ENGINE PRESSURE SENSOR RETURN

ENGINE PRESSURE SENSOR +5V

ENGINE INJECTION ACTUATION PRESSURE

ENGINE PRESSURE SENSOR RETURN

ENGINE PRESSURE SENSOR +5V

ENGINE ATMOSPHERIC PRESSURE

ENGINE PRESSURE SENSOR RETURN

ENGINE PRESSURE SENSOR +5V

E6

ENGINE OIL PRESSURE SENSOR

ENGINE OIL PRESSURE SENSOR RETURN

ENGINE OIL PRESSURE SENSOR +5V

ENGINE OIL LEVEL

ENGINE OIL LEVEL RETURN

ENGINE COOLANT TEMPERATURE

ENGINE TEMPERATURE SENSOR RETURN

ENGINE INTAKE MANIFOLD AIR TEMPERATURE

ENGINE TEMPERATURE SENSOR RETURN

D6

L984-OR

A703-BR

C
B
A

C200

C
B
A

C204

C203

C
B
A

C201

C
B
A

J304 P304J303 P303

B
A

INJECTOR
CYLINDER
NO.4

A746-PK
G829-GN
G828-WH

G849-BR
G829-GN
G828-WH

A747-GY
G829-GN
G828-WH

994-GY
G827-BU
G826-BR

1
2

J802 P802

1
2

J100 P100

1
2

J103 P103

G458-GY

�G829-GN

995-BU
G833-PK

C967-BU
G833-PK

L984-OR

B
A

INJECTOR
CYLINDER
NO.5

A704-GN

E5

TO ENGINE CYLINDER HEAD

(NOT CYLINDER HEAD GROUND STUD)

GROUND STUD

D5

L985-YL

J306 P306J305 P305

B
A

INJECTOR
CYLINDER
NO.6

A705-BU

TOP CAMSHAFT ENGINE
SPEED/TIMING SENSOR

BOTTOM CAMSHAFT ENGINE
SPEED/TIMING SENSOR

INTAKE AIR

L985-YL

A706-GY

INJECTION ACTUATION

PRESSURE CONTROL VALVE

TOP CAMSHAFT SPEED/TIMING­TOP CAMSHAFT SPEED/TIMING+

BOTTOM CAMSHAFT SPEED/TIMING­BOTTOM CAMSHAFT SPEED/TIMING+

ENGINE TIMING CALIBRATION PROBE+
ENGINE TIMING CALIBRATION PROBE-

K995-OR

HEATER

(IAPCV)

INTAKE AIR HEATER
RELAY

P300 J300

J501 P501

1
2

12
11
10

9
8
7

6
5
4
3
2
1

A
B

J500 P500

E4

A
B

J401 P401

A
B

J402 P402

A
B

J400 P400

C987-RD
G850-BU

ENGINE HARNESS CONNECTOR

L983-WH
L984-OR
L985-YL
A706-GY
A705-BU
A704-GN
A703-BR
A702-PU
A701-GY

G854-PK
G855-PU

A746-PK
G849-BR

A747-GY
G829-GN
G828-WH

994-GY
G827-BU
G826-BR

G883-GN
G458-GY

995-BU

C967-BU

G833-PK

E963-BK
E964-WH

E965-BU
E966-YL

G856-WH
G857-YL

NOTE A

G850-BU

D4

P648

G850-BU

B

C987-RD

A

P2 J2

INJECTOR RETURN CYLINDERS 1 & 2

44

INJECTOR RETURN CYLINDERS 3 & 4

45

INJECTOR RETURN CYLINDERS 5 & 6

46

INJECTOR CYLINDER 6

55

INJECTOR CYLINDER 5

54

INJECTOR CYLINDER 4

39

INJECTOR CYLINDER 3

38

INJECTOR CYLINDER 2

37

INJECTOR CYLINDER 1

36
47
67
68

1
63
64
4
5

IAP CONTROL VALVE

61

IAP CONTROL VALVE RETURN

62
70
40

ENGINE BOOST PRESSURE

27

ENGINE INJECTION ACTUATION PRESSURE
6
7

ENGINE ATMOSPHERIC PRESSURE

14

ENGINE PRESSURE SENSOR RETURN

3

ENGINE PRESSURE SENSOR +5V

2
15
16
17

ENGINE OIL PRESSURE SENSOR

24

ENGINE OIL PRESSURE SENSOR RETURN

42

41

ENGINE OIL PRESSURE SENSOR +5V

25
51
52

53

INPUT #16

60

ENGINE OIL LEVEL SWITCH

33
32

ENGINE COOLANT TEMPERATURE
35

ENGINE INTAKE MANIFOLD AIR TEMPERATURE
9
34
26
18

ENGINE TEMPERATURE SENSOR RETURN
10
11
12

TOP CAMSHAFT SPEED/TIMING-

49

TOP CAMSHAFT SPEED/TIMING+

48
13
50
19

BOTTOM CAMSHAFT SPEED/TIMING-

59

BOTTOM CAMSHAFT SPEED/TIMING+

58

28
29
30

31
43

ENGINE TIMING CALIBRATION PROBE+

22

ENGINE TIMING CALIBRATION PROBE-

23
56
57
65
66
69
20
21

INTAKE AIR HEATER RELAY

8

ENGINE CONTROL MODULE

ECM GROUND STRAP

TO ECM
MOUNTING
BOLT

E3

D3

E2

D2

E1

D1

F

E

D

C

B

(Dimensions: 25 inches x 24 inches)

RENR1368-06

12 Page,

A

CIRCUITS WITHIN THIS AREA ARE RECOMMENDATIONS

ENGINE

BLOCK

KEY SWITCH

ALTERNATOR

GROUND

NOTE A

NOTE A

NOTE A

NOTE A

NOTE A

NOTE A

NOTE A

C7

B7

COMPONENTS WITHIN THIS AREA ARE CATERPILLAR PROVIDED

A7

RELAY

OFF

ON

START

STARTER

MOTOR
(12V)

-

12V

BATTERY 3 BATTERY 1

NOTE A

(PEDAL RELEASED POSITION)

ACCELERATOR PEDAL SENSOR/SWITCH SENSOR RETURN

-

+ +

12V

BATTERY 2

H795-PK

CRUISE CONTROL ON/OFF SWITCH

CLUTCH PEDAL POSITION SWITCH N/C

H795-PK

A/C HIGH PRESSURE SWITCH N/C

H795-PK

ACCELERATOR PEDAL POSITION

SENSOR ACCELERATOR

PEDAL POSITION

C6

-

12V

TO ALLISON AT/MT/HT SHIFT
MODULATOR FOR AUTOMATIC
TRANSMISSIONS

B6

C975-WH

A6

3126B & 3126E OEM VEHICLE ELECTRICAL SCHEMATIC

N/O

+

(PEDAL RELEASED POSITION)

C977-BU

E971-GN

+8 V

100A WITH 130A PEAK AT 11V

K995-OR

C987-RD

H795-PK

SET/RESUME SWITCH

SERVICE BRAKE PEDAL POSITION SWITCH N/C

H795-PK

DIAGNOSTIC ENABLE SWITCH

H795-PK

N/O MOMENTARY SWITCH

B

BK
RD
WH

A
C

J403 P403

H795-PK
C985-BU
C986-BR

C992-PU

G844-PK

CHECK ENGINE

LAMP

WARNING LAMP

FAST IDLE

ENABLED LAMP

OR

WAIT TO

START LAMP

EXHAUST BRAKE

SOLENOID

J1939 SHIELD

C978-BR
C979-OR

INTAKE AIR

HEATER LAMP

C987-RD

L994-YL

659-PK

C5

G880-PK

FLYBACK
DIODE

9 PIN CAB

CONNECTOR

+BAT.

B

-BAT.

A
J
H

J1587 -

G

J1587 +

F
E

J1939 -

D

J1939 +

C

NOTE A

20A

B5

+BAT.

+BAT.

NOTE A

NOTE A

TACHOMETER

NOTE A

E793-BU
E794-YL
A249-BK
K990-GN
K900-YL

NOTE A

FAST IDLE ENABLE SWITCH

H795-PK

SERVICE BRAKE PEDAL POSITION SWITCH #2 N/O

TRANSMISSION NEUTRAL SWITCH N/O

PASSIVE MAGNETIC

VEHICLE SPEED

A5

COOLING FAN SOLENOID

B
A

J648

NOTE A

EXHAUST BRAKE ON/OFF SWITCH

SIGNAL+

NOTE A

SIGNAL-

450-YL

451-BR

N/O MOMENTARY SWITCH

NOTE A

(TRANSMISSION IN GEAR)

NOTE A

G808-BU
G809-GN

FLYBACK
DIODE

G882-WH

SENSOR

NOTE A

SPEEDOMETER

SIGNAL+

SIGNAL-

L902-GN

(PEDAL RELEASED POSITION)

409-OR

C974-PU

C973-GN

14 AWG GXL
14 AWG GXL
14 AWG GXL
14 AWG GXL

1
2

NOTE A: THIS IS AN OPTIONAL FEATURE NOT INSTALLED ON ALL VEHICLES.

659-PK

C4

NOTE A

NOTE A

B4

A4

L994-YL

K998-BU
G880-PK

E718-PK
E991-GY

G836-WH

C981-GY

C974-PU

C973-GN

NOTE A

993-BR
F713-OR

450-YL
451-BR

E793-BU
E794-YL
A249-BK
K990-GN
K900-YL

J906-BR

101-RD
101-RD
229-BK

229-BK
G838-BR
G839-BU

C978-BR
C979-OR
K999-GN
K980-PK
L902-GN
G840-PU
C975-WH
K982-YL
G841-GN

C992-PU

G842-GY
G882-WH
G843-OR
L901-GY
C977-BU

G879-OR

G844-PK
C983-WH
C984-YL
409-OR

E971-GN

G808-BU
G809-GN
G845-PU
H795-PK
C985-BU
C986-BR
G837-YL

P1 J1

MACHINE HARNESS CONNECTOR

NOTE A: THIS IS AN OPTIONAL FEATURE NOT INSTALLED ON ALL VEHICLES.

ENGINE CONTROL MODULE

29

WARNING LAMP

28

CHECK ENGINE LAMP

30

OUTPUT #1

31

OUTPUT #9
48
61
10

OUTPUT #2
12

OUTPUT #3
13

OUTPUT #4
15

EXHAUST BRAKE ON/OFF SWITCH

16
63
36

SPEEDOMETER POSITIVE
37

SPEEDOMETER NEGATIVE
27
26
3

INPUT SENSOR RETURN #2
17

INPUT #14

TACHOMETER POSITIVE

38

TACHOMETER NEGATIVE

39
57
43
9

J1587 DATA LINK NEGATIVE
8

J1587 DATA LINK POSITIVE
42

J1939 DATA LINK SHIELD
34

J1939 DATA LINK NEGATIVE
50

J1939 DATA LINK POSITIVE
1
14
70

IGNITION KEY SWITCH
25

52

UNSWITCHED +BATTERY
53

UNSWITCHED +BATTERY
65

-BATTERY

67

-BATTERY

19

OUTPUT #6
20

OUTPUT #7
51

SET

35

RESUME

44

INPUT #1 (PTO ON/OFF SWITCH)

56

INPUT #2

58

INPUT #18

40

OUTPUT #8

21

CRUISE CONTROL ON/OFF SWITCH

59

INPUT #3

60

INPUT #4

7

SERVICE BRAKE PEDAL POSITION SWITCH

45
55

INPUT #5

47

INPUT #13

64

INPUT #6

6

18

INPUT SENSOR RETURN #1
22

CLUTCH PEDAL POSITION SWITCH
23
2

+5V
46

INPUT #7
49

ENGINE COOLANT LEVEL NORMAL
54

ENGINE COOLANT LEVEL LOW
62

INPUT #12
24

INPUT #11

41
69

VEHICLE SPEED IN POSITIVE

32

VEHICLE SPEED IN NEGATIVE

33

INPUT #8 (REMOTE ACCELERATOR)

68

AP SENSOR/SWITCH SENSOR RETURN

5

+8V

4

ACCELERATOR PEDAL POSITION

66

OUTPUT #5

11

C3

B3

A3

C2

B2

SYMBOL DESCRIPTION

CIRCUIT CONNECTED

CIRCUIT NOT CONNECTED

ELECTRICAL CONNECTION TO
MACHINE STRUCTURE

INTERNAL ELECTRICAL CONNECTION
TO SURFACE OF COMPONENT

CONNECTOR

H#

CIRCUIT GROUPING DESIGNATION

ATCH WIRE, CABLE, COMPONENT

/

SPLICE

BLADE, SPADE, RING OR SCREW
TERMINAL

A2

THIS SCHEMATIC IS FOR THE 3126B AND 3126E ON-HIGHWAY ENGINE
ELECTRICAL SYSTEM

MEDIA NUMBER: RENR1368-06

Components are shown installed on a fully operable engine in a non powered state.
Refer to the appropriate Service Manual for Troubleshooting, Specifications and Systems Operations.

Refer to the Parts Manual using a specific serial number prefix in SIS before ordering parts from this schematic.

ABBREV

RD

WH

OR

YL

PK

BK

GY

PU

BR

GN

BU

C1

WIRE GROUP COLOR DESCRIPTIONS

(+) BATTERY

(+) BATTERY SWITCHED

STARTING CIRCUIT

(-) BATTERY / SENSOR RETURN

SENSOR / ACTUATOR SUPPLY

SIGNAL TO ECM

CONTROL (POSITIVE) FROM ECM

CONTROL (RETURN) FROM ECM

J1587/J1939 DATA LINK

OTHER COLOR DESCRIPTIONS

HIGHWAYS

COLOR

RED

WHITE

ORANGE

YELLOW

PINK

BLACK

GRAY

PURPLE

BROWN

GREEN

BLUE

B1

ALL WIRES TO BE 18 AWG OR LARGER SAE J1560 TYPE TXL
OR EQUIVALENT. FOR TWISTED PAIR SPECIFICATION SEE J1708.

Do not operate or work on this product unless you have
read and understood the instruction and warnings in the
relevant Operation and Maintenance Manuals and
relevant service literature. Failure to follow the instruc­tions or heed the warnings could result in injury or
death. Proper care is your responsibility.

A1

C

B

A

67

12345

ENGINE

INJECTION ACTUATION

PRESSURE SENSOR

INJECTOR HARNESS

GROMMET

INTAKE AIR HEATER

TOP VIEW

INTAKE MANIFOLD AIR
TEMPERATURE
SENSOR

ATMOSPHERIC
PRESSURE
SENSOR

BOOST
PRESSURE
SENSOR

INJECTION ACTUATION

PRESSURE SENSOR

INJECTOR HARNESS

GROMMET

INTAKE AIR HEATER

INTAKE MANIFOLD

AIR

TEMPERATURE

SENSOR

ATMOSPHERIC

PRESSURE

SENSOR

(SELECT RATINGS ONLY)

BOOST
PRESSURE
SENSOR

ENGINE HARNESS
CONNECTOR
J2/P2

INJECTION ACTUATION

PRESSURE CONTROL

VALVE

INLET AIR
HEATER
RELAY

ENGINE GROUND
STUD CONNECTION

INJECTION ACTUATION

PRESSURE CONTROL

ENGINE SPEED/TIMING

ENGINE GROUND
STUD CONNECTION

MACHINE HARNESS
CONNECTOR
J1/P1

VALVE

(IAPCV)

SENSORS

COOLANT

TEMPERATURE

SENSOR

OIL PRESSURE

SENSOR

(OPTIONAL)

OIL LEVEL

SWITCH

(OPTIONAL)

ENGINE
CONTROL
MODULE

LEFT SIDE VIEW