R2900G Load Haul Dump Power Train Electronic Control System Caterpillar

Illustration 1	g03159457
Schematic of the parking brake pressure sensor circuit

This diagnostic code means that the Power Train Electronic Control Module (ECM) has determined that the parking brake pressure sensor voltage is above normal.

This sensor is a Pulse Width Modulated (PWM) sensor that uses a frequency of approximately 500 Hz. The duty cycle operates from a range of 10% to 90%. See Systems Operation, "Sensors" for information regarding the operation and location of the sensor.

Possible causes of this diagnostic code are:

• Sensor signal circuit is open

• Sensor signal circuit is shorted to +battery

• Sensor failure

• Power or ground circuit failure

• ECM failure. The ECM is unlikely to fail

Note: The following test procedure may create other diagnostic codes. Ignore these codes, correct the original code, then clear these created codes. Ensure that the CID 2976 FMI 03 is active before performing this procedure.

Note: Use a calibrated digital multimeter for this procedure.

Test Step 1. CHECK FOR POWER

The sensor remains connected to the harness.

1. Turn on the disconnect switch and the keyswitch.

2. At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe along voltage supply wire (117-OR(Orange)) at contact 1.

3. Measure the voltage from contact 1 to frame ground.

Expected Result:

The voltage is 8 V.

Results:

• YES - The voltage is 8 V. Proceed to Test Step 2.

• NO - The voltage is not 8 V. The +battery circuit in the harness has failed.

  Repair: Correct a tripped circuit breaker.

  If a circuit breaker has not tripped, replace or repair the harness.

  STOP

Test Step 2. CHECK FOR GROUND

The sensor remains connected to the harness.

1. Turn off the keyswitch and the disconnect switch.

2. Remove the 7X-1710 Multimeter Probe from the voltage supply wire (117-OR(Orange)).

3. At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe along sensor return wire (C241-OR(Orange)) at contact 2.

4. Measure the resistance from contact 2 to frame ground.

Expected Result:

The resistance is less than 5 ohms.

Results:

• YES - The resistance is less than 5 ohms. Proceed to Test Step 3.

• NO - The resistance is greater than 5 ohms. The ground circuit has failed.

  Repair: Replace or repair the harness.

  STOP

Test Step 3. CHECK FOR AN OPEN

The switches remain off.

1. Disconnect the harness from the sensor.

2. At the harness connector for the sensor, connect a jumper wire between contact 2 (C241-BK(Black)) and contact 3 (K491-WH(White)).

3. Disconnect the harness connectors from the ECM.

4. At the harness connector for the ECM, measure the resistance between contact J2-40 (wire C491-PU(Purple)) and contact J1-45 (wire 118-OR(Orange)).

Expected Result:

The resistance is less than 5 ohms.

Results:

• YES - The resistance is less than 5 ohms. Proceed to Test Step 4.

• NO - The resistance is greater than 5000 ohms. The harness is open.

  Repair: Repair or replace the harness.

  STOP

Test Step 4. CHECK FOR A SHORT TO THE +BATTERY CIRCUIT

The switches remain off.

The sensor remains disconnected from the harness.

The harness connectors remain disconnected from the ECM.

1. Remove the jumper wire that was installed in the previous step.

2. At the machine harness connector for the ECM, measure the resistance from the signal contact J2-24 (wire K491-WH(White)) of the harness to all contacts in the harness connectors for the ECM.

Expected Result:

Each resistance is greater than 5 ohms.

Results:

• YES - Each resistance is greater than 5 ohms. Proceed to Test Step 5.

• NO - A resistance is less than 5 ohms. There is a short between signal contact J2-24 (wire K491-WH(White)) and the circuit with low resistance.

  Repair: Repair or replace the harness.

  STOP

Test Step 5. CHECK THE SENSOR OUTPUT

1. Reconnect the harness connectors to the ECM.

2. Reconnect the harness connector to the sensor.

3. At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe along the signal wire at contact 3.

4. At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe along the sensor return wire at contact 2.

5. Turn on the disconnect switch and the key switch.

6. Measure the sensor signal. The proper signal is described at the beginning of this procedure.

Expected Result:

The sensor signal is correct.

Results:

• YES - The sensor signal is correct. Proceed to Test Step 6.

• NO - The sensor signal is not correct. The sensor has failed.

  Repair: Replace the sensor.

  STOP

Test Step 6. INSPECT THE HARNESS

1. Turn off the keyswitch and the disconnect switch.

2. Inspect the sensor circuit wiring for the following:

   1. Inspect the connectors, pins, and sockets for the following:

      • Cleanliness

      • Security

      • Proper mating

      • Seal condition

      • Moisture

      • Corrosion

   2. Inspect the wires at the connector for the following:

      • Security

      • Nicks

      • Abrasion

      Note: Take care not to pull the wire out of the connector.

   3. Inspect the harness for the following:

      • Damage

      • Abrasion

      • Kinks

Expected Result:

The harness is in good condition.

Results:

• YES - The harness is in good condition. The ECM may have failed.

  Repair: Exit this procedure.

  Perform this procedure again.

  If the failure is not found, contact your dealer. If ECM replacement is required, see Systems Operation Troubleshooting Testing and Adjusting, "Electronic Control Module (Power Train) - Replace".

  STOP

• NO - The harness is not in good condition.

  Repair: Repair or replace the harness.

  STOP