Caterpillar Monitoring System for Electronic Modular Control Panel Caterpillar

Procedure

Locate the suspect sensor. Identify the sensor wires and connector contacts. See Testing and Adjusting, "Pulse Width Modulated (PWM) Sensor - Test". DO NOT DISCONNECT ANY HARNESS CONNECTORS AT THIS TIME. Turn the ECS to the COOLDOWN position. DO NOT START THE ENGINE.

1. Check the sensor power.

   1. At the sensor connector, identify the +Battery circuit and the ground circuit.

   2. Push the 7X-1710 Cable Probes in the back of the sensor connector. Place the probes along the side of the + Battery wire and the ground wire.

   3. Measure the system voltage.

      Expected Result: The voltage that is measured is between 7.5 and 8.5 DCV.

      Results:

      • YES - The voltage is between 7.5 and 8.5 DCV. The system voltage is present. Proceed to 2.

      • NO - The voltage is not between 7.5 and 8.5 DCV. There is an open circuit. Trace the +Battery circuit and trace the ground circuit in the engine harness. Repair the engine harness or replace the engine harness. STOP.

2. Check the signal voltage.

   1. At the sensor connector, identify the signal circuit and the ground circuit.

   2. Push the 7X-1710 Cable Probes in the back of the sensor connector. Place the probes along the side of the signal wire and the ground wire.

   3. Measure the signal voltage and record the signal voltage.

      Expected Result: The signal voltage that is measured is between approximately 1.0 and 7.0 DCV.

      Results:

      • FROM 1.0 TO 7.0 DCV - The voltage is between approximately 1.0 and 7.0 DCV. The signal voltage at the sensor is correct. Proceed to 3.

      • GREATER THAN 7.0 - The voltage is NOT between approximately 1.0 and 7.0 DCV. The signal voltage is not correct. Proceed to 4.

      • LESS THAN 1.0 DCV - The voltage is less than 1.0 DCV. Proceed to 5.

3. Check the signal circuit of the engine harness.

   1. At the engine harness connector for the main display module, identify the signal circuit and the ground circuit. DO NOT DISCONNECT THE HARNESS CONNECTOR.

   2. Push the 7X-1710 Cable Probes in the back of the engine harness connector along side of the signal wire and the ground circuit wires.

   3. Measure the signal voltage.

   4. Compare this measurement with the voltage that was measured in the previous test "Check the signal voltage".

      Expected Result: The comparison is identical to the voltages from the previous test "Check the signal voltage".

      Results:

      • OK - The voltage is the same as in the previous test "Check the signal voltage". The main display module is receiving a valid signal voltage. If the problem still persists, further testing is required. See Testing and Adjusting, "Sensor Dynamic Test". Proceed to 6.

      • NOT OK - Voltage is not the same as in the previous test "Check the signal voltage". The engine harness has an open in the signal circuit or the ground circuit. Repair the engine harness or replace the engine harness. STOP.

4. Check the engine harness.

   1. Signal voltage is greater than 7.0 DCV. The probable cause is a short to system voltage (+battery) in the engine harness. Another cause could be a faulty sensor.

   2. Disconnect the engine harness connector for the sensor.

      Expected Result: The voltage that is measured is greater than 6.0 ± 0.5 DCV.

      Results:

      • YES - The voltage is greater than 6.0 ± 0.5 DCV. The voltage is not correct. The signal circuit of the engine harness is shorted to the +battery. Repair the engine harness or replace the engine harness. If the engine harness is not faulty, replace the main display module. STOP.

      • NO - The voltage is 6.0 ± 0.5 DCV. The voltage is correct for a good harness and the main display module. The sensor is faulty. Replace the sensor. STOP.

5. Check the engine harness.

   The signal voltage is less than 1.0 DCV. The probable cause is a short to ground in the engine harness or the sensor is faulty.

   1. Disconnect the engine harness connector for the sensor.

   2. Measure the voltage between the signal contact and the ground contact.

      Expected Result: The voltage that is measured is less than 6.0 ± 0.5 DCV.

      Results:

      • YES - The voltage is less than 6.0 ± 0.5 DCV. The voltage is not correct. The signal circuit of the engine harness is shorted to ground. Repair the engine harness or replace the engine harness. If the engine harness is not faulty, replace the main display module. STOP.

      • NO - The voltage is 6.0 ± 0.5 DCV. The voltage is correct for a good harness and the main display module. The sensor is faulty. Replace the sensor. STOP.

6. Perform the Sensor Dynamic Test.

   Results:

   • OK - STOP.