C7 Engine for the AP-755 Asphalt Paver and the PM-102 Cold Planer Caterpillar

Use this procedure to troubleshoot any suspect problems with the 8 V digital supply.

This procedure covers the following diagnostic code:

• 41-03 8 Volt DC Supply short to +batt

• 41-04 8 Volt DC Supply short to ground

The digital sensor supply in the Electronic Control Module (ECM) supplies 8.0 ± 0.5 VDC to the throttle position sensor and to the coolant level sensor.

The digital sensor supply is output short circuit protected. The ECM is protected from a short to ground and a short to +Battery condition. The digital sensor is not protected.

Illustration 1	g01249651
Schematic

Illustration 2	g01251599
P1 ECM connector (P1-4) +8 V digital supply (P1-5) Digital return (P1-46) Coolant level (PM102Y) (P1-66) Throttle position

Illustration 3	g01094844
Sensor connector

Test Step 1. Inspect Electrical Connectors and Wiring

1. Remove the electrical power from the ECM.

2. Thoroughly inspect the J1/P1 ECM connector, the machine connector, the connector for the throttle position sensor and the connector for the coolant level sensor. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".

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

4. Check the ECM connector (allen head screw) for the proper torque. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".

5. Check the harness and wiring for abrasion and for pinch points from the sensors back to the ECM.

Expected Result:

All connectors, pins, and sockets are completely inserted and coupled. The harness and wiring are free of corrosion, of abrasion, and of pinch points. All connections and grounds are tight and free of corrosion.

Results:

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

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

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.Verify that the repair eliminates the problem.

  STOP

Test Step 2. Check for Active Diagnostic Codes

1. Connect Caterpillar Electronic Technician (ET) to the service tool connector.

2. Restore the electrical power to the ECM.

3. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes.

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

Expected Result:

One of the following diagnostic codes is active:

• 41-03

• 41-04

Results:

• OK - A -03 diagnostic code is active. Proceed to Test Step 3.

• OK - A -04 diagnostic code is active. Proceed to Test Step 4.

• Not OK - No diagnostic code for the digital supply is active. A problem is suspected with a sensor output signal. In order to verify that the sensor is receiving the correct supply voltage, proceed to Test Step 3.

Test Step 3. Check the Voltage on the +8 V Supply Wire

1. Remove the electrical power from the ECM.

2. Disconnect all of the digital sensor at the sensor connectors.

3. Restore the electrical power to the ECM.

4. Measure the voltage between terminal A and terminal B at each sensor connector.

Expected Result:

The voltage is 8.0 ± 0.5 VDC.

Results:

• OK - The voltage is 8.0 ± 0.5 VDC. The voltage is correct.

  Repair: Reconnect the sensors. Clear all diagnostic codes. Check for active diagnostic codes. If the problem is intermittent, refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - The voltage is not 8.0 ± 0.5 VDC. The voltage is incorrect. Proceed to Test Step 5.

Test Step 4. Disconnect the +8 V Sensor while you Monitor the Active Diagnostic Codes

1. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes.

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

2. Disconnect the digital sensors one at a time from the sensor connectors. Wait for 30 seconds after each sensor is disconnected. Check for an active diagnostic code on Cat ET.

Expected Result:

The -04 diagnostic code deactivates.

Results:

• OK - The -04 diagnostic code deactivates after a particular sensor is disconnected.

  Repair: Reconnect the sensor. If the problem returns after the reconnection of the sensor, disconnect the sensor. If the problem disappears after the disconnection of the sensor, replace the sensor. Clear all diagnostic codes. Verify that the repair eliminates the problem.

  STOP

• Not OK - The -04 diagnostic code stays active. Leave the sensors disconnected. Proceed to Test Step 5.

Test Step 5. Check the +8 V Supply Wire for a Short to Engine Ground or a Short to another Wire in the Harness

1. Remove the electrical power from the ECM.

2. Disconnect the J1/P1 and J2/P2 ECM connector.

3. Leave the digital sensors disconnected.

Note: Wiggle the harness during the following measurements in order to reveal any intermittent short condition.

4. Measure the resistance between P1-4 (+8 V digital supply) and every terminal on ECM connector P1 and ECM connector P2.

   1. Measure the resistance between P1-4 (+8 V digital supply) and engine ground.

Expected Result:

Each resistance measurement indicates an open circuit.

Results:

• OK - The resistance measurement does not indicate a short in the engine harness or a short to engine ground. Proceed to Test Step 6.

• Not OK - A resistance measurement does not indicate an open circuit. The +8 V digital supply wire is shorted in the engine harness or the +8 V digital supply wire is shorted to engine ground.

  Repair: Repair the wire or replace the wire. Clear all logged diagnostic codes. Replace all wires to the original configuration. Verify that the repair eliminates the problem.

  STOP

Test Step 6. Check the +8 V Supply and the Sensor Return for an Open Circuit

1. Install a wire jumper between pin P1-4 (+8 V digital supply) and pin P1-5 (digital return).

Note: Wiggle the harness during the following measurements in order to reveal any intermittent short condition.

2. Measure the resistance between terminal A and terminal B at each of the sensor connectors.

3. Remove the wire jumper.

Expected Result:

The resistance is less than 10 Ohms for each measurement.

Results:

• OK - The resistance check does not indicate an open circuit in the engine harness. Proceed to Test Step 7.

• Not OK - A resistance measurement is greater than 10 Ohms. The +8 V digital supply wire or the sensor common has excessive resistance.

  Repair: Repair the wires or replace the wires. Clear all logged diagnostic codes. Verify that the repair eliminates the problem.

  STOP

Test Step 7. Check the +8 V Supply at the ECM

1. Remove the wire from ECM connector P1-4 (+8 V digital supply). Install a wire jumper with socket terminals on both ends into P1-4.

2. Remove the wire from ECM connector P1-5 (digital return). Install a wire jumper with socket terminals on both ends into P1-5.

3. Reconnect ECM connector J1/P1.

4. Restore the electrical power to the ECM.

5. Measure the voltage between the wire jumper in P1-4 and the wire jumper in P1-5.

6. Remove the electrical power from the ECM.

7. Reconnect all wires to the original configuration.

Expected Result:

The voltage is 8.0 ± 0.5 VDC.

Results:

• OK - The voltage is 8.0 ± 0.5 VDC. The voltage is correct.

  Repair: The ECM is OK. Clear all diagnostic codes. Check for active diagnostic codes. If the problem is intermittent, refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - The voltage is not 8.0 ± 0.5 VDC. The voltage is incorrect.

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

  STOP