3512 and 3516 EUI Engines for 784B, 785B, 789B and 793B Off-Highway Trucks Caterpillar

Use this test when there are active occurrences or logged occurrences of CID-FMI: 168-00, 168-01 and 168-02. 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 Electronic Control Module (ECM). Verify that there are no problems with the starting system or with the charging system before you use this test.

There are two +Battery connections and two -Battery connections to the ECM. These multiple lines will reduce the resistance at the harness. The ECM receives battery voltage through a 15 Amp breaker when the main power relay is energized. The current draw from the batteries is approximately 3 Amp when the keyswitch is in the ON position and the engine is running. The current draw from the batteries is zero when the keyswitch is in the OFF position.

Illustration 1	g00935708

Test Step 1. Check for Connector Damage

1. Turn the keyswitch to the OFF position.

2. Thoroughly inspect the ECM connector J1/P1 and the machine connector J2/P2. Inspect all of the other connectors. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.

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 of 2.25 ± 0.25 N·m (20 ± 2 lb in).

5. Check the machine connector (allen head screw) for the proper torque of 2.25 ± 0.25 N·m (20 ± 2 lb in).

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

Expected Result:

The connectors and wiring are free of the following problems: damage, corrosion, abrasion and incorrect attachment.

Results:

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

• Not OK - The connectors and/or wiring need repair.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring.

  Stop.

Test Step 2. Check the Voltage at the Battery Post.

1. Turn the keyswitch to the ON position. The engine should be off.

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

3. 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: There is a problem with the batteries or with the charging system. Refer to the manual Testing and Adjusting for further information.

  Stop.

Test Step 3. Check the Voltage to the ECM.

1. Turn the keyswitch to the OFF position. The engine should be off.

2. Remove ECM connector J1/P1.

3. Turn the keyswitch to the ON position. The engine should be off.

4. Measure the voltage between P1-57 and P1-2 at the ECM connector P1.

5. Measure the voltage between P1-70 and P1-13 at the ECM connector P1.

6. Turn the keyswitch to the OFF position. The engine should be off.

Expected Result:

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

Results:

• OK - The voltage is ± 1 VDC from the voltage at the battery terminals. The voltage at the ECM is okay. Proceed to Test Step 6.

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

Test Step 4. Check the Voltage at the Coil of the Main Power Relay.

1. Turn the keyswitch to the OFF position. The engine should be off.

2. Remove wire 308-YL from the coil of the main power relay.

3. Turn the keyswitch to the ON position. The engine should be off.

4. Measure the voltage between wire 308-YL and engine ground.

5. Turn the keyswitch to the OFF position. The engine should be off.

6. Reconnect all wires and connectors.

Expected Result:

The voltage is 24 ± 3 VDC on wire 308-YL at the main power relay.

Results:

• OK - The voltage is 24 ± 3 VDC at the main power relay.

  Repair: Check for voltage on wire 112-PU at the main power relay.

  1. If voltage is present on wire 112-PU at the main power relay, check for voltage at the breaker for the engine control.

     1. If voltage is present on wire 112-PU at the breaker for the engine control, repair the breaker for the engine control or repair the wire 150-OR between the ECM and the breaker for the engine control.

     2. If voltage is not present on wire 112-PU at the breaker for the engine control, repair wire 112-PU between the main power relay and the breaker for the engine control.

  2. If voltage is not present on wire 112-PU, check for voltage on wire 109-RD on the main power relay.

     1. If voltage is not present on wire 109-RD on the main power relay, repair the wire between the battery and the main power relay.

     2. If voltage is present on wire 109-RD check the wire 200-BK to ground from the main power relay. If the wire to ground is okay, replace the main power relay.

  Stop.

• Not OK - The voltage is not 24 ± 3 VDC on wire 308-YL at the main power relay. Proceed to Test Step 5.

Test Step 5. Check the Voltage at the Keyswitch.

1. Turn the keyswitch to the ON position. The engine should be off.

2. Measure the voltage between terminal R and engine ground at the keyswitch.

3. Turn the keyswitch to the OFF position. The engine should be off.

Expected Result:

The voltage is 24 ± 3 VDC on terminal R of the keyswitch.

Results:

• OK - The voltage measures 24 ± 3 VDC on terminal R of the keyswitch.

  Repair: The problem is in the wire 308-YL between the keyswitch and the main power relay. Repair the connectors or wiring and/or replace the connectors or wiring.

  Stop.

• Not OK - The voltage does not measure 24 ± 3 VDC on terminal R of the keyswitch.

  Repair: Check for 24 ± 3 VDC at terminal B of the keyswitch.

  1. If voltage is present on terminal B of the keyswitch, replace the keyswitch.

     1. If voltage is not present on terminal B of the keyswitch, verify that the breaker for the keyswitch is not tripped. Verify that the breaker for the alternator is not tripped. Repair the wiring and/or terminals between the following circuit components: keyswitch, breaker for the keyswitch, breaker for the alternator and battery.

  Stop.

Test Step 6. Check the Analog Sensor Power Supply.

1. Turn the keyswitch to the OFF position. The engine should be off.

2. Remove wire 997-OR from ECM connector P1-65. Install a jumper into the socket for P1-65.

3. Remove wire 993-BR from ECM connector P1-23. Install a jumper into the socket for P1-23.

   Note: The analog return will no longer be connected to the other sensors and switches. Additional diagnostic codes will be generated from the ECM. Clear the codes after you complete this test.

4. Turn the keyswitch to the ON position. The engine should be off.

5. Measure the voltage between P1-65 and P1-23.

6. Remove the jumper wires and reconnect all wires.

Expected Result:

The voltage is 5 ± 0.2 VDC.

Results:

• OK - The voltage is 5 ± 0.2 VDC. Proceed to Test Step 7.

• Not OK - The voltage is not 5 ± 0.2 VDC.

  Repair: The analog supply is not functioning properly. Replace the ECM with a new ECM. Refer to the diagnostic procedure Troubleshooting, "Replacing the ECM".

  Stop.

Test Step 7. Check the Digital Sensor Supply.

1. Turn the keyswitch to the OFF position. The engine should be off.

2. Remove wire A700-OR from ECM connector P1-51. Install a jumper into the socket for P1-51.

3. Remove wire 998-BR from ECM connector P1-9. Install a jumper into the socket for P1-9.

   Note: The digital return will no longer be connected to the other sensors and switches. Additional diagnostic codes will be generated from the ECM. Clear the codes after you complete this test.

4. Turn the keyswitch to the ON position. The engine should be off.

5. Measure the voltage between P1-51 and P1-9.

6. Remove the jumper wires and reconnect all wires.

Expected Result:

The voltage is 12.7 ± 1.0 VDC.

Results:

• OK - The voltage is 12.7 ± 1.0 VDC.

  Repair: The electrical power supplies are operating correctly. If the problem is intermittent, perform the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".

  Stop.

• Not OK - The voltage is not 8 ± 0.4 VDC.

  Repair: The digital supply is not functioning properly. Replace the ECM with a new ECM. Refer to the diagnostic procedure Troubleshooting, "Replacing the ECM".

  Stop.