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

The Permanent Timing Calibration Sensor is used to calibrate the signal from the Speed/Timing Sensor against Top Center (TC) on the flywheel.

Illustration 1	g00651337

Test Step 1. Check for Connector Damage.

1. Turn the keyswitch to the OFF position.

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

3. Thoroughly inspect the connectors J1/P1 and J2/P2 of the Electronic Control Module (ECM). 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 wiring and connectors are okay. Proceed to test step 2.

• Not OK - The wiring and/or connectors need repair.

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

  Stop.

Test Step 2. Check for an Open Circuit in the Timing Calibration Sensor.

1. Disconnect the connector for the timing calibration sensor J26/P26.

2. Measure the resistance between J26-1 and J26-2.

Expected Result:

The resistance should be between 110 to 200 Ohms.

Results:

• OK - The resistance is between 110 Ohms to 200 Ohms. Proceed to test step 3.

• Not OK - The resistance is not between 110 to 200 Ohms. The sensor is internally shorted or open.

  Repair: Replace the sensor.

  Stop.

Test Step 3. Check for a Short Circuit in the Timing Calibration Sensor.

1. Measure the resistance between J26-1 and the engine ground.

2. Measure the resistance between J26-2 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 4.

• Not OK - The resistance is less than 20,000 Ohms. The sensor is internally shorted.

  Repair: Replace the sensor.

  Stop.

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

1. Disconnect ECM connector J1/P1.

2. Measure the resistance between P26-1 and P26-2.

3. Measure the resistance between P26-1 and the engine ground.

4. Measure the resistance between P26-2 and the engine ground.

Expected Result:

The resistance should be greater than 20,000 Ohms for each measurement.

Results:

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

• Not OK - The resistance is less than 20,000 Ohms indicating a short circuit.

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

  Stop.

Test Step 5. Check for an Open Circuit in the Wiring Harness.

1. Use a suitable piece of wire and connect P26-1 to P26-2 at the connector for the timing calibration sensor.

2. Measure the resistance between P1-18 and P1-12 at the ECM connector P1.

Expected Result:

The resistance should be less than 10 Ohms through the wires.

Results:

• OK - The resistance is less than 10 Ohms through the wires. Proceed to test step 6.

• Not OK - The resistance is more than 10 Ohms through the wires. There is an open circuit in the harness or connectors.

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

  Stop.

Test Step 6. Check the Signal Voltage at the Connector for the Timing Calibration Sensor.

1. Reconnect the sensor connector J26/P26.

2. Remove wire F723-PK from ECM connector P1-18.

3. Remove wire F724-PU from ECM connector P1-12.

4. Turn the circuit breaker for the engine to the ON position.

5. Turn the keyswitch to the START position.

6. Start the engine.

7. Decelerate the engine to low idle.

8. Set a multimeter on the 20 VAC position.

9. Measure the voltage between wire F723-PK and F724-PU that were removed from P1-18 and P1-12.

10. Turn the keyswitch to the OFF position.

11. Replace all wires and replace all connectors.

Expected Result:

The signal voltage should be greater than 6.0 VAC.

Results:

• OK - A valid signal voltage appears at the ECM connector P1. Proceed to test step 7.

• Not OK - There is a problem in the harness or the sensor.

  Repair: Recheck for shorts or opens in the harness. If the problem is not resolved, adjust the air gap to approximately 0.9 mm (0.04 inch) and repeat this test.

  Stop.

Test Step 7. Check for "ACTIVE" Diagnostic Codes.

1. Turn the keyswitch to the ON position.

2. Start the Caterpillar Electronic Technician (ET).

3. Check for ACTIVE diagnostic codes.

Expected Result:

The diagnostic code 261-13 should NOT be active.

Results:

• OK - The sensor is working properly.

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

  Stop.

• Not OK - A valid signal voltage appears at P1. The ECM is not reading the voltage properly.

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

  Stop.