3412, 3412C, and 3412E Generator Set Engines Caterpillar

The Electronic Control Module (ECM) receives electrical power through the customer connector (J14/P14). Typically, the ECM is powered whenever the engine control switch is turned to the ON position. Aftermarket engine protection devices are often wired in order to interrupt supply voltage to the ECM. Check for proper installation and operation of the engine protection devices.

Use this test if there are intermittent engine shutdowns or if a difficulty in starting is not accompanied by loss of electrical accessories. Engine shutdowns that are accompanied by a loss of other electrical accessories indicate a problem in the keyswitch. This does not indicate a problem in the wiring at the engine's ECM. Verify that there are no problems with the starting system or the charging system before you use this test.

Illustration 1	g01626598

Illustration 2	g01635537
(1) + Battery (21) - Battery

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 the diagnostic code in the Table is active or easily repeated.

Test Step 1. Inspect the Electrical Connectors and the Wiring Harness

1. Remove electrical power from the ECM.

2. Thoroughly inspect the ECM connector J14/P14. Also, inspect connector J17/P17. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

3. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the Power Supply.

4. Check the allen head screw on the ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.

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 OK. Proceed to Test Step 2.

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

  Repair: Repair the wiring and connectors or replace the wiring or the connectors. Ensure that all of the seals are properly connected. Verify that the repair eliminates the problem.Verify that the repair eliminates the problem.

  STOP

Test Step 2. Check Battery Voltage at the Battery

1. Turn the engine control switch to the OFF position.

2. Turn the circuit breaker for the battery to the OFF position.

3. Measure no-load battery voltage at the battery terminals. Refer to Testing and Adjusting, "Test Tools for the Electrical System" for the proper procedures to check the batteries.

4. Load test the battery. Use the 4C-4911 Battery Load Tester .

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. Refer to Systems Operation/Testing and Adjusting.

  STOP

Test Step 3. Check the Voltage to the ECM

1. Disconnect the ECM connector J14/P14.

2. Turn the circuit breaker for the battery to the ON position.

3. Turn the engine control switch to the ON position.

4. Measure the voltage between the following pins.
   • P14-1 and P14-21

   • P17-19 and P17-13

Expected Result:

The voltage measures 24 ± 3 VDC.

Results:

• OK - The ECM is receiving the correct battery voltage.

  Repair: The problem may be intermittent. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - The voltage is incorrect at the connection to the ECM. The wiring or components between the battery and the ECM are preventing the voltage from reaching the ECM. Proceed to Test Step 4.

Test Step 4. Check Voltage at the Circuit Breaker

1. Turn the circuit breaker for the battery to the ON position.

2. Turn the engine control switch to the ON position.

3. Measure voltage from both terminals of the breaker to engine ground.

Expected Result:

The voltage measures 24 ± 3 VDC on both terminals.

Results:

• OK - The voltage measures 24 ± 3 VDC on both terminals. If the voltage is only present on one of the terminals, replace the fuse.

  Repair: The problem may be intermittent. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - The voltage does not measure 24 ± 3 VDC on both terminals.

  Repair: The fuse or the breaker is in need of repair or replacement.

  STOP