3512C Engine Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the signal from the fuel position multiplier or if the diagnostic code in Table 1 is active or easily repeated.

The fuel position multiplier is an external input to the ECM. The input reduces the available fuel rack according to the magnitude of the signal. The fuel position multiplier can be considered as an external derating of engine power. Typically, the input is a means for reducing the engine power without changing the throttle signal.

The ECM reads a Pulse Width Modulated signal (PWM) that is similar to the throttle signal. Usually, a converter is used to change the signal from the torque limit control into a PWM signal. An increase in the duty cycle reduces the available fuel. For example, if the engine power output is 100 percent and the signal from the fuel position multiplier is set to 75 percent, the engine power output is reduced by 25 percent.

The fuel position multiplier affects the available fuel rack instantly. The signal is applied in addition to any active derating of the engine power. For example, if the engine is presently derated by 10 percent due to high exhaust temperature and the signal from the fuel position multiplier has a duty cycle of 50 percent, the engine power output is reduced by a total of 60 percent. If the signal has a duty cycle that is between 0 and 10 percent or between 96 and 100 percent, the multiplier is 1.0 (100 percent). If the signal has a duty cycle that is between 90 and 95 percent, the multiplier is 0.0 (0 percent).

Illustration 1	g01382929
Typical schematic

Illustration 2	g01214513
P2 ECM connector (P2-69) Fuel position multiplier

Illustration 3	g01382931
Customer connector (Terminal 1) Fuel position multiplier

Illustration 4	g01234146
Location of ECM connectors

Test Step 1. INSPECT THE ELECTRICAL CONNECTORS AND THE WIRING

1. Turn the main disconnect switch to the OFF position.

2. Thoroughly inspect the ECM connector J2/P2. Inspect all of the other connectors. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" for details.

3. Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

4. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.

5. Check the harness and the wiring for abrasion and pinch points.

Expected Result:

All connectors, pins and sockets are completely coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion and of pinch points.

Results:

• OK - The harness and connectors appear to be OK. Proceed to Test Step 2.

• Not OK - There is a problem with the connectors and/or wiring.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring.

  STOP

Test Step 2. CHECK THE WIRING FROM THE FUEL POSITION MULTIPLIER

1. Disconnect the fuel position multiplier.

2. Connect a throttle position sensor or a device that will generate a 500 Hz PWM signal. Connect the attachment directly to the wiring that sends the PWM signal to the ECM.

3. Turn the main disconnect switch to the ON position.

4. Start Caterpillar Electronic Technician (ET).

5. Observe the fuel position multiplier and the throttle signal on Cat ET. Set the fuel position multiplier to 0.0. Adjust the throttle from the minimum to the maximum throttle. Record the results.

6. Observe the fuel position multiplier and the throttle on Cat ET. Set the fuel position multiplier to 0.5. Adjust the throttle from the minimum to the maximum throttle. Record the results.

7. Observe the fuel position multiplier and the throttle on Cat ET. Set the fuel position multiplier to 1.0. Adjust the throttle from the minimum to the maximum throttle. Record the results.

8. Turn the main disconnect switch to the OFF position.

9. Restore the wiring to the original configuration.

Expected Result:

The throttle on Cat ET varies from 0 percent to 100 percent when the fuel position multiplier is set at 0.0.

The throttle on Cat ET varies from 0 percent to 50 percent when the fuel position multiplier is set at 0.5.

The throttle on Cat ET is 0 percent when the fuel position multiplier is set at 1.0.

Results:

• OK - The ECM is reading the fuel position multiplier correctly. The wiring between the fuel position multiplier and the ECM is OK.

  Repair: The problem appears to be the fuel position multiplier or the connector for the fuel position multiplier. Refer to the OEM manual.

  STOP

• Not OK - The ECM is not reading the fuel position multiplier correctly. There is a problem in the wiring between the fuel position multiplier and the ECM. Proceed to Test Step 3.

Test Step 3. CHECK THE SIGNAL INPUT TO THE ECM

1. Remove wire F722-BK(Black) from ECM connector P2-69.

2. Connect a throttle position sensor or a device that will generate a 500 Hz PWM signal. Connect the attachment directly to ECM connector P2-69.

3. Reconnect the ECM connector J2/P2.

4. Turn the main disconnect switch to the ON position.

5. Start Cat ET.

6. Observe the fuel position multiplier and the throttle signal on Cat ET. Set the fuel position multiplier to 0.0. Adjust the throttle from the minimum to the maximum throttle. Record the results.

7. Observe the fuel position multiplier and the throttle on Cat ET. Set the fuel position multiplier to 0.5. Adjust the throttle from the minimum to the maximum throttle. Record the results.

8. Observe the fuel position multiplier and the throttle on Cat ET. Set the fuel position multiplier to 1.0. Adjust the throttle from the minimum to the maximum throttle. Record the results.

9. Remove electrical power from the ECM.

10. Restore the wiring to the original configuration.

Expected Result:

The throttle on Cat ET varies from 0 percent to 100 percent when the fuel position multiplier is set at 0.0.

The throttle on Cat ET varies from 0 percent to 50 percent when the fuel position multiplier is set at 0.5.

The throttle on Cat ET is 0 percent when the fuel position multiplier is set at 1.0.

Results:

• OK - The ECM is reading the fuel position multiplier correctly.

  Repair: The problem is in the wiring and/or connectors between the ECM and the fuel position multiplier. Repair the connector and/or wiring or replace the connector and/or wiring.

  STOP

• PWM Reading NOT OK - The reading for the fuel position multiplier is not correct on Cat ET.

  Repair: The problem appears to be in the ECM. Replace the ECM. Refer to Troubleshooting, "ECM - Replace".

  STOP