3500B Engines for Caterpillar Built Power Modules with the ADEM 3 Electronic Control Module Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the power to the engine's Electronic Control Module (ECM) or if any one of the diagnostic codes in Table 1 is active or easily repeated. Refer to Troubleshooting, "Event Code List" for information about event codes and the default trip points for these codes. You must access the monitoring system on Caterpillar Electronic Technician (ET) in order to view the current trip points for these codes.

To reduce resistance in the wiring harness, there are three isolated power connections to the ECM. The connections must be complete in order to ensure proper engine operation. There is a constant power supply to the ECM when the engine is shutdown. In order to shut off the power to the ECM, the battery power needs to be disconnected or the ECM relay needs to be energized.

Illustration 1	g01443822
Typical schematic

Illustration 2	g01382168
P1 ECM connector (P1-52) +Battery (P1-53) +Battery (P1-55) +Battery (P1-63) −Battery (P1-65) −Battery (P1-67) −Battery (P1-70) Keyswitch

Illustration 3	g01234146
Location of ECM connectors

Test Step 1. Inspect Electrical Connectors and Wiring

1. Turn the battery disconnect switch to the OFF position.

2. Thoroughly inspect the ECM connectors J1/P1. Inspect all of the connections on the customer connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the proper procedure for inspecting system wiring.

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

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

5. Check the harness and the wiring for abrasion and for pinch points.

Expected Result:

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

Results:

• OK - The harness and wiring are 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 the Battery Voltage

1. Measure no-load voltage at the battery posts. Refer to Systems Operation/Testing and Adjusting for the proper procedures to check the batteries.

2. Load test the batteries. Use the 4C-4911 Battery Load Tester. Refer to the Operating Manual, SEHS9249. Refer to Special Instruction, SEHS7633.

Expected Result:

The no-load voltage at the batteries is at least 23.5 VDC, and the batteries pass the load test.

Results:

• OK - The no-load voltage at the batteries is at least 23.5 VDC, and the batteries pass the load test. Proceed to Test Step 3.

• Not OK - The no-load voltage at the batteries is less than 23.5 VDC, and/or the batteries fail the load test.

  Repair: The batteries or the alternator are causing the problem. Recharge the batteries or replace the batteries. Verify that the original condition is resolved. Refer to Systems Operation/Testing and Adjusting for information on the charging system.

  STOP

Test Step 3. Check the Voltage at the ECM Connector

1. Disconnect the J1/P1 ECM connector.

2. Turn the battery disconnect switch to the ON position.

3. Wiggle the harness during the following test steps in order to find an intermittent condition.

   1. Measure the voltage between P1-52 (Unswitched Positive Battery) and P1-63 (Negative Battery).

   2. Measure the voltage between P1-53 (Unswitched Positive Battery) and P1-65 (Negative Battery).

   3. Measure the voltage between P1-55 (Unswitched Positive Battery) and P1-67 (Negative Battery).

   4. Measure the voltage between P1-70 (Keyswitch) and P1-63 (Negative Battery).

4. Turn the battery disconnect switch to the OFF position.

5. Replace all wires and connectors to the original configuration.

Expected Result:

The voltage is ± 1 VDC from the voltage at the battery posts.

Results:

• OK - The ECM is receiving the correct voltage.

  Repair: If an intermittent condition is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - The voltage is not ± 1 VDC from the voltage at the battery posts. Proceed to Test Step 4.

Test Step 4. Check the Output Voltage of the ECM Relay

1. Turn the battery disconnect switch to the ON position.

2. Measure the voltage between terminal 87A of the ECM relay and the minus battery terminal of the power distribution box.

Expected Result:

The voltage is ± 1 VDC from the voltage at the battery posts.

Results:

• OK - The voltage is ± 1 VDC from the voltage at the battery posts.

  Repair: The problem is in the wiring and/or connectors between the ECM relay and the ECM. Use continuity checks in order to find the open or the short in the harness.

  STOP

• Not OK - The voltage is not ± 1 VDC from the voltage at the battery posts. Proceed to Test Step 5.

Test Step 5. Check the Supply Voltage of the ECM Relay

1. Measure the voltage between terminal 30 of the ECM relay and the minus battery terminal of the power distribution box.

Expected Result:

The voltage is ± 1 VDC from the voltage at the battery posts.

Results:

• OK - The voltage is ± 1 VDC from the voltage at the battery posts.

  Repair: The ECM relay has failed. Replace the relay.

  STOP

• Not OK - The voltage is not ± 1 VDC from the voltage at the battery posts.

  Repair: The problem is in the supply circuit to the ECM relay. Ensure that the breaker for the ECM relay has not tripped or that the relay has not failed. Ensure that all connections are tight and that all connections are free of corrosion. Repair the circuit. Verify that the repair has resolved the original problem.

  STOP