IT38G Series II Integrated Toolcarrier and 938G Series II Wheel Loader Caterpillar

Illustration 1	g00826618
Schematic of the Secondary Steering Pressure Switch

CID 0794 FMI 03 diagnostic code can only be recorded if the optional secondary steering system is installed. The primary steering pressure switch is connected to two inputs of the ECM. One contact is open and the other contact is grounded during proper operation.

This FMI 03 means that the ECM has determined that both contacts are open.

Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear the diagnostic codes when the original diagnostic code is corrected.

Note: Ensure that the diagnostic code indicator is active and that the diagnostic code is active.

Test Step 1. CHECK THE GROUND CIRCUIT OF THE SWITCH IN THE HARNESS

1. Turn the key start switch and the disconnect switch to the OFF position.

2. Disconnect the machine harness connector(s) from the ECM.

3. Measure the resistance between contact J1-16 (wire 962-OR) of the machine harness for the ECM and the contact A (wire 962-OR) .

Expected Result:

The resistance is less than 5 ohms.

Results:

• OK - The resistance is less than 5 ohms. The circuit is correct. Proceed to Test Step 2.

• NOT OK - The resistance is greater than 5000 ohms. The circuit is open. The machine harness has failed.

  Repair: Repair the machine harness or replace the machine harness.

  Stop.

Test Step 2. CHECK THE SWITCH CIRCUITS FOR A SHORT TO THE +BATTERY CIRCUIT

1. The machine harness connector(s) remains disconnected from the ECM.

2. The disconnect switch and the key start switch remain in the OFF position.

3. Disconnect the connector for the switch from the machine harness.

4. At the machine harness connector for the ECM, measure the resistance from contact J1-38 (wire 453-PK) and contact J2-11 (wire 416-OR) of the machine harness to all the contacts that are used in the machine harness connectors for the ECM.

Expected Result:

Each resistance measurement is greater than 5000 ohms.

Results:

• YES - Each resistance measurement is greater than 5000 ohms. The harness is correct. Proceed to Test Step 3.

• NO - One or more of the measurements were less than 5 ohms. There is a short in the machine harness.

  Repair: The short is between wire 453-PK and the circuit with the lowest resistance measurement, or the short is between wire 416-OR and the circuit with the lowest resistance measurement. Repair the machine harness or replace the machine harness.

  Stop.

Test Step 3. CHECK THE SWITCH CIRCUITS IN THE HARNESS

1. The machine harness remains disconnected from the ECM and the switch.

2. At the harness connector for the switch, connect a jumper wire between contact C (wire 453-PK) and contact B (wire 416-OR).

3. At the harness connector for the ECM, measure the resistance from contact J1-38 (wire 453-PK) to contact J2-11 (wire 416-OR).

Expected Result:

The resistance is less than 5 ohms.

Results:

• OK - The resistance is less than 5 ohms. Proceed to Test Step 4.

• NOT OK - The resistance is greater than 5000 ohms. The circuit is open.

  Repair: The machine harness has failed. Repair the machine harness or replace the machine harness.

  Stop.

Test Step 4. CHECK THE OPERATION OF THE SWITCH (LOW PRESSURE)

Note: Do NOT run the engine during this Test Step. This will cause low system pressure to the primary steering pressure switch.

1. Remove the jumper that was installed in the previous Test Step.

2. The machine harness remains disconnected from the switch.

3. Connect one lead from a multimeter to contact A (wire 962-OR) of the harness connector for the switch.

4. Connect the other lead from a multimeter to contact B (wire 416-OR) of the harness connector for the switch.

5. Measure the resistance between contact A (wire 962-OR) and contact B (wire 416-OR). Note the resistance.

6. Disconnect the lead from contact B (wire 416-OR) and connect the lead to contact C (wire 453-PK).

7. Measure the resistance between contact A (wire 962-OR) and contact C (wire 453-PK).

Expected Result:

The resistance from contact A to contact C is less than 5 ohms, and the resistance from contact A to contact B is greater than 5000 ohms.

Results:

• YES - The resistance from contact A to contact C is less than 5 ohms, and the resistance from contact A to contact B is greater than 5000 ohms. The switch is operating correctly. Proceed to Test Step 5.

• NO - The resistance from contact A to contact C is not less than 5 ohms, or the resistance from contact A to contact B is not greater than 5000 ohms. The switch has failed.

  Repair: Replace the switch.

  Stop.

Test Step 5. CHECK THE OPERATION OF THE SWITCH (HIGH PRESSURE)

1. Start the engine. This will cause the system pressure to activate the primary steering pressure switch.

2. Connect one lead from a multimeter to contact A (wire 962-OR) of the harness connector for the switch.

3. Connect the other lead from a multimeter to contact B (wire 416-OR) of the harness connector for the switch.

4. Measure the resistance between contact A (wire 962-OR) and contact B (wire 416-OR). Note the resistance.

5. Disconnect the lead from contact B (wire 416-OR) and connect the lead to contact C (wire 453-PK).

6. Measure the resistance between contact A (wire 962-OR) and contact C (wire 453-PK).

Expected Result:

The resistance from contact A to contact B is less than 5 ohms, and the resistance from contact A to contact C is greater than 5000 ohms.

Results:

• YES - The resistance from contact A to contact B is less than 5 ohms, and the resistance from contact A to contact C is greater than 5000 ohms. The switch is operating correctly. Proceed to Test Step 6.

• NO - The resistance from contact A to contact B is not less than 5 ohms, or the resistance from contact A to contact C is not greater than 5000 ohms. The switch has failed.

  Repair: Replace the switch.

  Stop.

Test Step 6. CHECK IF THE DIAGNOSTIC CODE REMAINS

1. Inspect the contacts of the harness connectors and clean the harness connectors.

2. Reconnect all the harness connectors.

3. Turn the disconnect switch and the key start switch to the ON position.

4. Operate the machine.

5. Check the status of the CID 0794 FMI 03.

Expected Result:

The CID 0794 FMI 03 is active.

Results:

• YES - The CID 0794 FMI 03 is active. The diagnostic code has not been corrected. The ECM may have failed.

  Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, replace the ECM. See Troubleshooting, "Electronic Control Module (ECM) - Replace".

  Stop.

• NO - The CID 0794 FMI 03 is not active. The diagnostic code does not exist at this time.

  Repair: The initial diagnostic code was probably caused by a poor electrical connection or a short at one of the harness connectors that was disconnected and reconnected. Resume normal machine operation.

  Stop.