C9 Marine Engines Caterpillar

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

This procedure covers the following diagnostic codes:

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

• 41-04 8 Volt DC Supply short to ground

The digital sensor supply is output short circuit protected. A short circuit to the battery should not cause permanent damage to the circuit inside the Electronic Control Module (ECM). The coolant level sensor is not protected from overvoltage.

The digital sensor supply provides a regulated voltage of 8.0 ± 0.4 VDC to the coolant level sensor.

Illustration 1	g01192829
Schematic

Illustration 2	g01093894
Typical location of the coolant level sensor (1) Coolant level sensor

Illustration 3	g01093451
P2 ECM connector (P2-4) +8 V digital sensor power (P2-5) Digital sensor return (P2-6) Coolant level sensor

Test Step 1. Inspect Electrical Connectors and Wiring

1. Remove the electrical power from the ECM and thoroughly inspect the J2/P2 ECM connector and the J1/P1 ECM connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

2. Perform a 45 N (10 lb) pull test on each of the wires in the circuit that is associated with the digital sensor supply.

3. Check the J1/P1 ECM allen head screw connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

4. Check the harness and wiring for abrasions and for pinch points from the battery to the ECM.

Expected Result:

All connectors, pins, and sockets are completely coupled and/or inserted, and the harness and wiring are free of corrosion, of abrasion and of pinch points.

Results:

• OK - The connectors and wiring are okay. Proceed to Test Step 2.

• Not OK - There is a problem with the connectors 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.

  STOP

Test Step 2. Check for Active Diagnostic Codes

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

2. Restore the electrical power to the ECM.

3. Monitor the active diagnostic code screen on the electronic service tool. 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 41-03 diagnostic code is active. Proceed to Test Step 3.

• OK - A 41-04 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 the coolant level sensor at the sensor connector.

3. Restore the electrical power to the ECM.

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

Expected Result:

The voltage is 8.0 ± 0.4 VDC.

Results:

• OK - The voltage is 8.0 ± 0.4 VDC. The voltage is correct.

  Repair: Replace all wires to the original configuration. Clear all diagnostic codes. Check for active diagnostic codes. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - The voltage is not 8.0 ± 0.4 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 the electronic service tool. 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 coolant level sensor at the sensor connector.

3. Wait for 30 seconds after the sensor is disconnected. Check for an active diagnostic code on the electronic service tool.

Expected Result:

The 41-04 diagnostic code deactivates.

Results:

• OK - The 41-04 diagnostic code deactivates. The diagnostic code is not active after the 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. Replace all wires to the original configuration. Clear all diagnostic codes. Verify that the repair eliminates the problem.

  STOP

• Not OK - The 41-04 diagnostic code stays active. Leave the sensor 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/P1 ECM connectors.

3. Leave the digital sensor disconnected at the sensor connector.

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

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

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

Expected Result:

The resistance is more than 20,000 Ohms.

Results:

• OK - The resistance is more than 20,000 Ohms. 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 is less than 20,000 Ohms. The +8 V supply wire is shorted in the engine harness or the +8 V 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 Common for an Open Circuit

1. Install a wire jumper between pin P2-4 (+8 V Supply) and pin P2-5 (Sensor Common).

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 the connector for the coolant level sensor.

3. Remove the wire jumper.

Expected Result:

The resistance is less than five Ohms.

Results:

• OK - The resistance is less than five Ohms. The resistance measurement does not indicate an open circuit in the engine harness. Proceed to Test Step 7.

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

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

  STOP

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

1. Remove the wire R800-OR from ECM connector P2-4 (+8 V Supply). Install a wire jumper with socket terminals on both ends into P2-4.

2. Remove the wire J842-BK from ECM connector P2-5 (sensor return). Install a wire jumper with socket terminals on both ends into P2-5.

3. Reconnect ECM connector J2/P2.

4. Restore the electrical power to the ECM.

5. Measure the voltage between the wire jumper in P2-4 and the wire jumper in P2-5.

6. Remove the electrical power from the ECM.

7. Replace all wires to the original configuration.

Expected Result:

The voltage is 8.0 ± 0.4 VDC.

Results:

• OK - The voltage is 8.0 ± 0.4 VDC. The voltage is correct.

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

  STOP

• Not OK - The voltage is not 8.0 ± 0.4 VDC. The voltage is incorrect.

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

  STOP