3516B Engine for 994F and 994H Wheel Loaders Caterpillar

Use this test when there are active occurrences or logged occurrences of diagnostic codes. 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 and 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.

Use this procedure to troubleshoot the electrical system if a problem is suspected with the power to the engine ECM. Also, use this procedure if any one of the diagnostic codes in Table 1 is active or easily repeated.

Unswitched battery voltage is supplied to the ECM at P1-52 and P1-53. The negative battery is supplied to the ECM at P1-63 and P1-65. The ECM receives the input from the keyswitch at P1-70 when the keyswitch is in the ON position or in the START position. When the ECM detects battery voltage at this input, the ECM will power up. When battery voltage is removed from this input, the ECM will power down. The ECM continuously receives battery voltage through the circuit breaker for the ECM.

The ECM requires the keyswitch to be in the ON position in order to maintain communications with Caterpillar Electronic Technician (ET).

Illustration 1	g01145646
Typical schematic

Test Step 1. Inspect Electrical Connectors and Wiring

1. Check all circuit breakers.

2. Turn the keyswitch to the OFF position.

Show/hide table



Illustration 2	g01234146
Location of ECM connectors

3. Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect the connections for the battery and the connections to the keyswitch. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

Show/hide table



Illustration 3	g01526167
P1 ECM connector (P1-52) +Battery (P1-53) +Battery (P1-63) −Battery (P1-65) −Battery (P1-70) Keyswitch

4. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector and the sensor connectors that are associated with the active diagnostic code.

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

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

Expected Result:

All connectors, pins, and sockets are 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 coupled.Verify that the repair eliminates the problem.

  STOP

Test Step 2. Check the Batteries

1. Measure the no-load battery voltage at the battery posts.

2. Load - test the batteries. Use the 4C-4911 Battery Load Tester. Refer to Special Instruction, SEHS9249, "Use of 4C-4911 Battery Load Tester for 6, 8 V and 12 V Lead Acid Batteries" and Special Instruction, SEHS7633, "Battery Test Procedure".

Expected Result:

The batteries pass the load test. The measured voltage is the minimum specification for a 12V or 24V system.

Results:

• OK - The batteries are OK. Proceed to Test Step 3.

• Not OK - The battery voltage is low or the battery did not pass the load test.

  Repair: Recharge or replace the faulty batteries. Verify that the repair eliminates the problem.

  STOP

Test Step 3. Check the Voltage at the ECM

1. Disconnect the J1/P1 ECM connector.

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

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

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

Expected Result:

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

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 - Keyswitch voltage out of range - Proceed to Test Step 4.

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

  Repair: There is an open circuit or excessive resistance in the wiring or connections between the batteries and the ECM. Verify that the circuit breaker for the ECM is not tripped. Verify that the battery disconnect switch is in the ON position. Verify that the connection for the engine ground is clean and tight. Repair the connectors or wiring and/or replace the connectors or wiring.

  STOP

Test Step 4. Check the Voltage from the Keyswitch to the ECM

1. Turn the keyswitch to the OFF position.

2. Remove the wire from the terminal R of the keyswitch.

3. Turn the keyswitch to the ON position.

4. Measure the voltage on terminal B of the keyswitch to engine ground.

5. Measure the voltage on terminal R of the keyswitch to engine ground.

6. Turn the keyswitch to the OFF position.

Expected Result:

Voltage is present on terminal B and terminal R at the keyswitch.

Results:

• OK - Voltage is present on terminal B and terminal R at the keyswitch.

  Repair: If voltage is present on terminal R, repair the wire between the keyswitch and the ECM. Verify that the problem is eliminated.

  STOP

• Not OK - Voltage is not present on terminal B at the keyswitch.

  Repair: If voltage is not present on terminal B, repair the wire between the +Battery and the keyswitch. Verify that the breaker for the keyswitch is not tripped. Verify that the problem is eliminated.

  STOP

• Not OK - Voltage is not present on terminal R at the keyswitch.

  Repair: If voltage is present on terminal B of the keyswitch but not present on terminal R, replace the keyswitch. Return all wiring to the original configuration. Verify that the problem is eliminated.

  STOP