3508B Engine for 854G Wheel Dozers and 992G Wheel Loaders Caterpillar

Depressing the right brake pedal will disable the throttle lock feature. The previous engine rpm that was set may be resumed by pressing the "Resume/Accel Switch".

The throttle lock feature eliminates fatigue from holding the throttle pedal down for extended periods of time. The throttle lock feature allows the operator to maintain a desired engine rpm without the use of the throttle pedal.

The engine's Electronic Control Module (ECM) will disable the throttle lock feature if the signals from the right brake switch are invalid. The throttle lock feature will remain disabled until the keyswitch is cycled from the OFF position to the ON position.

Illustration 1	g00910242

Test Step 1. Check for Connector Damage.

1. Turn the circuit breaker for the engine to the OFF position.

2. Turn the keyswitch to the OFF position.

3. Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" 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 ECM connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).

6. Check the customer connector (allen head screw) for the proper torque of 2.25 ± 0.25 N·m (20 ± 2 lb in).

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

Expected Result:

The connectors and wiring should be free of the following problems: damage, corrosion, abrasion and incorrect attachment.

Results:

• OK - The connectors and wiring are okay. Proceed to test step 2.

• Not OK - The connectors and/or wiring are not okay.

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

  Stop.

Test Step 2. Check the Right Brake Switch on the Caterpillar Electronic Technician (ET).

1. Install the Cat ET.

2. Turn the keyswitch to the ON position. The engine should be OFF.

3. Operate the right brake switch.

4. Observe the status of the right brake switch on the Cat ET.

Expected Result:

The right brake switch status should read "ON" when the right brake pedal is depressed. The right brake switch status should read "OFF" when the right brake pedal is released.

Results:

• OK - The right brake switch and all wiring is operating normally.

  Repair: If the problem is intermittent, perform the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".

  Stop.

• Not OK - The status of the right brake switch is incorrect on the Cat ET. Proceed to test step 3.

Test Step 3. Short the Wires at the Right Brake Switch.

Note: Record the position of the wires from the right brake switch before you remove the wires from the right brake switch.

1. Disconnect the wires from the right brake switch.

2. Connect a wire jumper between the wires F721-GY and 998-BR. Leave wire F722-OR open.

3. Turn the keyswitch to the OFF position.

4. Turn the keyswitch to the ON position. The engine should be OFF.

5. Observe the status of the right brake switch on the Cat ET.

6. Remove the wire jumper between wires F721-GY and 998-BR.

7. Connect a wire jumper between the wires F722-OR and 998-BR. Leave wire F721-GY open.

8. Turn the keyswitch to the OFF position.

9. Turn the keyswitch to the ON position. The engine should be OFF.

10. Observe the status of the right brake switch on the Cat ET.

11. Remove the wire jumper between wires F722-GY and 998-BR.

Expected Result:

The right brake switch status should read "OFF" when F721-GY and 998-BR are shorted together.

The right brake switch status should read "ON" when F722-OR and 998-BR are shorted together.

Results:

• OK - The ECM read the signal from the right brake switch correctly. The harness and the ECM are okay.

  Repair: Temporarily connect a new right brake switch. Verify that the new right brake switch solves the problem before permanently installing the new right brake switch.

  Stop.

• Not OK - The ECM did not read the signal from the right brake switch correctly. There is a problem in the harness or the ECM. Proceed to test step 4.

Test Step 4. Check for a Short Circuit in the Wiring Harness.

1. Turn the keyswitch to the OFF position.

2. Turn the circuit breaker for the engine to the OFF position.

3. Disconnect ECM connector J1/P1.

4. Set a multimeter on the 20,000 Ohm position.

5. Measure the resistance between P1-13 and P1-29.

6. Measure the resistance between P1-13 and P1-19.

7. Measure the resistance between P1-19 and P1-29.

8. Measure the resistance between P1-19 and the engine ground.

9. Measure the resistance between P1-13 and the engine ground.

Expected Result:

The resistance should be greater than 20,000 Ohms.

Results:

• OK - The resistance is greater than 20,000 Ohms. Proceed to test step 5.

• Not OK - The resistance is less than 20,000 Ohms. There is a short in the harness between the right brake switch and the ECM.

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

  Stop.

Test Step 5. Check the Resistance through the Harness.

1. Connect a wire jumper between the wires F722-OR and 998-BR at the right brake switch.

2. Set the multimeter on the 200 Ohm position.

3. Measure the resistance between P1-13 and P1-29.

4. Remove the wire jumper between wires F722-GY and 998-BR.

5. Connect a wire jumper between the wires F721-GY and 998-BR.

6. Measure the resistance between P1-19 and P1-29.

7. Remove the wire jumper between wires F721-GY and 998-BR.

Expected Result:

The resistance should be less than 10 Ohms for each measurement.

Results:

• OK - The resistance is less than 10 Ohms for each measurement. Proceed to test step 6.

• Not OK - The resistance is greater than 10 Ohms for each measurement. There is an open or excessive resistance in the harness.

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

  Stop.

Test Step 6. Short the Wires of the Right Brake Switch at the ECM.

1. Remove the wires from P1-13, P1-19 and P1-29 at the ECM connector P1.

2. Insert a wire with a socket terminal at each end into ECM connector P1-19 and P1-29.

3. Reconnect all connectors.

4. Turn the keyswitch to the ON position. The engine should be OFF.

   Note: Additional diagnostic codes will be generated because the digital return will no longer be connected to other sensors and switches. Ignore the codes and clear the codes when you have completed this test.

5. Observe the status of the right brake switch on the Cat ET.

6. Turn the keyswitch to the OFF position.

7. Disconnect J1/P1 and remove the wire short.

8. Insert a wire with socket terminals at each end into ECM connector P1-13 and P1-29.

9. Reconnect all the connectors.

10. Turn the keyswitch to the ON position. The engine should be OFF.

11. Observe the status of the right brake switch on the Cat ET.

12. Turn the keyswitch to the OFF position.

13. Remove the wire short.

14. Replace all wiring. Reconnect all connectors.

Expected Result:

The status of the right brake switch should read "OFF" when the wire short is inserted between P1-19 and P1-29.

The status of the right brake switch should read "ON" when the wire short is inserted between P1-13 and P1-29.

Results:

• OK - The ECM reads the correct signal when the jumper is at P1 but not at the right brake switch. The harness is faulty.

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

  Stop.

• Not OK - The correct signal for the right brake switch appears at P1 but the ECM is not reading the signal for the right brake switch properly.

  Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM".

  Stop.