Bendix Commercial Vehicle Systems ET-2 User Manual

Bendix® ET-2™ Electronic Treadle

SD-15-4106

TREADLE

COVER

POTENTIOMETER

PIVOT SPRING

MOUNTING BASE

CONNECTOR

FIGURE 1 - ET-2™ ELECTRONIC TREADLE

DOUBLE RETURN

SPRING

ROLLER

CABLE ASSEMBLY

DESCRIPTION

The ET-2™ is an electronic throttle. On electronically controlled diesel engines, the ET-2™ treadle fulfills the same function as a conventional mechanical throttle. The ET -2 treadle controls engine speed by interacting with an electronic fuel management controller on the engine, rather than transmitting a mechanical force from the throttle pedal to the engine governor.

The main components of the ET-2™ throttle are a cast aluminum mounting base and treadle, a rubber treadle cover, a potentiometer (variable resistor), and a roller assembly. The potentiometer is specific to each engine application.

OPERATION

The ET-2™ treadle provides smooth, graduated throttle control through the function of its variable resistor , or potentiometer. The ET-2™ treadle receives its supply voltage from the engine control unit. The lever shaft connects the roller assembly to the potentiometer, so that any movement of the treadle rotates the potentiometer. As the potentiometer rotates, its resistance changes. This way, the potentiometer communicates the throttle position to the fuel control

system by changing resistance, returning more or less of the supplied voltage back to the electronic engine controller.

If the driver does not request engine power, the throttle is in the idle (or “closed throttle”) position. In this state, the potentiometer significantly reduces the amount of supply voltage returned to the engine control unit (See Figure 2).

As the driver depresses the ET-2™ treadle, output voltage increases (see Figure 3). The potentiometer allows an increased amount of its supply voltage to return to the engine control unit, which in turn increases the engine’s speed.

In the full (or “open throttle”) position, the driver has fully depressed the ET-2™ treadle. This is the state of least potentiometer resistance. The ET-2™ treadle returns the maximum percentage of supply voltage to the engine control unit (see Figure 2).

Engine Idle Throttle Full Throttle

Manufacturer (Closed) (Open)

CAT 13 - 21% 79 - 89%

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Cummins 8 - 18% 70 - 80%

Detroit Diesel 6 - 14% 86 - 94%

Mack 10 - 20% 70 - 85%

FIGURE 2 - ET-2™ TREADLE OUTPUT VOLTAGE, AS A PERCENTAGE OF SUPPLY VOL TAGE

7 6

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ET-2

TREADLE

OUTPUT

VOLTAGE

FIGURE 3 - ET-2

5 4 3 2 1

CLOSED THROTTLE OPEN THROTTLE

○○○○○○○○○○○○○○○○○○○○○○○○○○○○

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TREADLE OUTPUT VOL TAGE

DETROIT

DIESEL

CAT

CUMMINS

MACK

Figure 3 illustrates the relationship between throttle position and engine RPM. Potentiometer performance will vary for each engine application, therefore potentiometers must not be interchanged.

WARNING! PLEASE READ AND FOLLOW THESE INSTRUCTIONS TO AVOID PERSONAL INJURY OR DEATH:

When working on or around a vehicle, the following general precautions should be observed at all times.

1. Park the vehicle on a level surface, apply the parking brakes, and always block the wheels. Always wear safety glasses.

2. Stop the engine and remove ignition key when working under or around the vehicle. When working in the engine compartment, the engine should be shut off and the ignition key should be removed. Where circumstances require that the engine be in operation, EXTREME CAUTION should be used to prevent personal injury resulting from contact with moving, rotating, leaking, heated or electrically charged components.

3. Do not attempt to install, remove, disassemble or assemble a component until you have read and thoroughly understand the recommended procedures. Use only the proper tools and observe all precautions pertaining to use of those tools.

4. If the work is being performed on the vehicle’s air brake system, or any auxiliary pressurized air systems, make certain to drain the air pressure from all reservoirs before beginning ANY work on the vehicle. If the vehicle is equipped with an AD-IS air dryer system or a dryer reservoir module, be sure to drain the purge reservoir.

5. Following the vehicle manufacturer’s recommended procedures, deactivate the electrical system in a manner that safely removes all electrical power from the vehicle.

6. Never exceed manufacturer’s recommended pressures.

7. Never connect or disconnect a hose or line containing pressure; it may whip. Never remove a component or plug unless you are certain all system pressure has been depleted.

8. Use only genuine Bendix® replacement parts, components and kits. Replacement hardware, tubing, hose, fittings, etc. must be of equivalent size, type and strength as original equipment and be designed specifically for such applications and systems.

9. Components with stripped threads or damaged parts should be replaced rather than repaired. Do not attempt repairs requiring machining or welding unless specifically stated and approved by the vehicle and component manufacturer.

10. Prior to returning the vehicle to service, make certain all components and systems are restored to their proper operating condition.

FIGURE 4 - EXPLODED VIEW

PREVENTIVE MAINTENANCE

GENERAL

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Perform the following tests and inspections at the prescribed intervals. If the ET-2™ treadle does not function as described, repair it or replace it with a new unit, available at any authorized Bendix parts outlet. EVERY 3 MONTHS, 25,000 MILES, OR 900 OPERA TING HOURS:

1. Remove any accumulated contaminants and visually inspect the exterior of the ET-2™ treadle for physical damage or excessive corrosion.

2. Inspect electrical connections and cable assembly for signs of corrosion, wear, or physical damage. Replace as necessary.

3. Inspect springs (11, 12, 13) for signs of corrosion or pitting. Replace as necessary.

4. Inspect bearings (10), washer (7), and snap rings (8) for cracks or deterioration. Replace as necessary.

OPERATIONAL TEST Perform these tests only if the vehicle’s throttle does not

appear to operate as expected. Test 1: For Mack and DDC engines:

1. Unplug the cable assembly from the potentiometer’s integral connector by lifting the lock tab and pulling the connectors until they disengage. Inspect cable assembly for loose terminals, frayed wires, corrosion,

POWER

SUPPLY

(9-16 VDC)

DIGITAL

VOLT/

OHM

METER

A B C

PACKARD ELECTRIC

CONNECTOR 12010717

(CONNECTOR X)

PIN C

RESISTOR

TEST LOAD (47,000 OHM FOR DETROIT DIESEL,

300,000 OHM

FOR MACK)

POTENTIOMETER

PC. NO. ON THIS

SURFACE

FIGURE 5 - ET-2™ TREADLE ELECTRICAL TEST SCHEMATIC FOR THE DETROIT DIESEL CONNECTOR

GROUND

PIN B VOUT

(OUTPUT)

PIN A VREF

(INPUT)

wear, or physical damage. Check end-to-end electrical continuity at terminals. NOTE: Potentiometer pin locations will remain constant (see Figure 5). However, cable assembly connector pin out may vary from engine to engine.

2. Remove the ET-2™ treadle from the vehicle.

3. Secure the ET-2™ treadle to a smooth, flat surface in such a way that it does not twist the unit.

4. Connect the potentiometer to the volt meter and power supply as shown in Figure 5. NOTE: Power supply can be a 12 VDC vehicle battery in good condition and with known voltage output.

5. Verify that the closed throttle (idle) output voltage, as a percentage of supply voltage, is within the limits listed in Figure 2.

6. Depress the treadle to its full throttle position. The output voltage, as a percentage of supply voltage, should be within the limits listed in Figure 2, e.g. Testing a Detroit Diesel ET -2™ Treadle Potentiometer: Battery = 10 VDC. Full throttle = 9 VDC. 9/10 x 100 = 90%.

7. Make several full applications and record idle position voltage each time. Verify that idle position voltage does not vary by more than .4% (.02 volts). If the ET-2 treadle does not operate within its specified ranges, service the unit, or replace it with a new ET-2™ treadle, available at your nearest Bendix parts outlet.

INPUT PIN 3

OUTPUT PIN 2

GROUND PIN 1

PACKARD ELECTRIC

CONNECTOR 12015793

C B A

FIGURE 6 - ET-2

SCHEMATIC FOR THE CUMMINS CONNECTOR

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TREADLE ELECTRICAL TEST

(CONNECTOR Y)

Test 2: For Cummins engines (featuring a separate potentiometer and idle validation switch):

T o test the potentiometer on the vehicle, use steps 1 through

8. Alternatively, instructions for carrying out a “bench test” is covered in instructions 1 1 through 16.

1. First construct the “breakout” harness shown in Figure 6.

2. Insert connector X on the breakout harness into the connector leading from the potentiometer. Then insert connector Y on the breakout harness into the connector leading from the dashboard wire harness.

3. Next insert pin 1 into the ground position on a voltmeter. Then insert pin 2 into the positive position on a volt meter.

4. Disconnect the idle validation switch cable from the dashboard wire harness. Connect an ohmmeter to pins A and B on the connector leading from the idle validation switch. The positive lead should be connected to pin A and the negative lead should be connected to pin B.

5. Turn the vehicle’s ignition key to the “battery on”

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position. This supplies a 5 volt input to the potentiometer. Since the idle validation switch is no longer connected, a fault code may be triggered on some vehicles. This fault code will be reset at the end of this test.

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