735B, 740B and 740B EJECTOR Articulated Trucks Chassis Electronic Control System Caterpillar

Illustration 1	g03275078
Schematic of the Front Cross Axle Lock and Interaxle Lock Accummulator Solenoids

The MID 087 CID 1674 FMI 03 diagnostic code is associated with the front cross axle lock and interaxle lock accumulator charge solenoids. The two solenoids share a common return. When the return is shorted to battery, shorted to ground, or open circuit, the failure is logged against the return signal instead of the Front Cross Axle Lock Solenoid or the Inter Axle Lock Accumulator Charge Solenoid.

Possible causes for this diagnostic code are:

• The Front Cross Axle Lock Solenoid energize circuit has shorted to a voltage source.

• The Chassis ECM may have failed. An ECM failure unlikely.

Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes now, but clear those codes after the original diagnostic code has been corrected.

Note: Poor connections are often the cause of a problem in electrical circuits. Before performing this procedure, inspect all of the harness connectors involved in the circuit. Verify that all of the connections in the circuit are clean, secure, and in good condition. If a problem is found with any of the connections: correct the problem and verify that diagnostic code CID 0969 FMI 03 is still active, before performing the following procedures.

System Response:

When this diagnostic code is active, the Chassis ECM will turn off the current to the failed solenoid.

Test Step 1. CHECK THE SOLENOID, THE ECM, AND THE CIRCUIT CONNECTIONS IN THE MACHINE HARNESS.

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

2. Disconnect the machine harness connector from the Front Cross Axle Lock solenoid.

3. At the harness connector for the solenoid, place a jumper wire from contact 1 (368-OR) to contact 2 (K927-BU) on the connector.

4. Turn the disconnect switch and the key start switch to the ON position. Do not start the engine.

5. Observe the status of the CID 0969 FMI 03 diagnostic code.

Expected Result:

The CID 0969 FMI 03 diagnostic code remains active.

Results:

• YES - The CID 0969 FMI 03 diagnostic code remains active. The jumper wire did not change the code. The solenoid is NOT the cause of the problem.

  Repair: The machine harness has failed, or the ECM may have failed.

  Proceed to Test Step 2.

• NO - The CID 0969 FMI 03 code is no longer active, and has been replaced by an active CID 0969 FMI 06 diagnostic code. The ECM has detected a valid diagnostic code.

  Repair: The ECM, and the harness connections, are correct. The solenoid has failed.Perform Test Step 1 again, to verify the solenoid failure. Replace the solenoid.

  Proceed to Test Step 3

Test Step 2. CHECK THE SOLENOID ENERGIZE CIRCUIT FOR A SHORT TO A VOLTAGE SOURCE.

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

2. The harness connector remains disconnected from the Front Cross Axle Lock solenoid.

3. Remove the jumper wire inserted in Test Step 1.

4. Disconnect the J1 and J2 machine harness connectors from the Chassis ECM.

5. At the ECM J1 harness connector, measure the resistance from contact J1-67 (368-OR) to all of the other contacts that are used in the machine harness connectors for the ECM.

Expected Result:

Each resistance is more than 5000 ohms.

Results:

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

• NO - Each resistance is NOT more than 5000 ohms. There is a short in the harness. The short is between contact J1-67 (368-OR) and the circuit with the low resistance.

  Repair: Repair, or replace, the harness.

  Proceed to Test Step 3.

Test Step 3. CHECK IF THE DIAGNOSTIC CODE IS STILL ACTIVE

1. Remove any jumper wires still inserted.

2. Reconnect all harness connectors. Make sure that the connectors are fully seated. Observe that the clips for each connector are securely fastened.

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

4. Clear all inactive diagnostic codes.

5. Operate the machine.

6. Check the status of the CID 0969 FMI 03 diagnostic code.

Expected Result:

The CID 0969 FMI 03 diagnostic code is no longer active.

Results:

• YES - The CID 0969 FMI 03 diagnostic code is no longer active. The code does not exist at this time.

  Repair: The cause for the diagnostic code appears to have been corrected. Return the machine back to normal operations.

  STOP

• NO - The CID 0969 FMI 03 diagnostic code is still active. The problem has NOT been corrected.

  Repair: If you have not inspected the harness connectors in a previous Test Step, do that now. Clean the contacts of the harness connectors. Check the wires for damage to the insulation caused by excessive heat, battery acid, or chafing.Perform a 45 N (10 lb.) pull test on each of the wires that are associated with the solenoid circuit.Perform a "wiggle test" on the solenoid circuit of the machine wiring harness, using the Caterpillar Electronic Technician service tool. The "wiggle test" can be used to detect open or shorted connections in the machine wiring harness.Reconnect all harness connectors. Make sure that the connectors are fully seated. Observe that the clips for each connector are fastened. Perform Test Step 3 again. If the problem has NOT been found, and this diagnostic code is still active, the ECM may have failed.Prior to replacing an ECM, always contact your Dealership Technical Communicator for possible consultation with Caterpillar, or with the Dealer Solutions Network. This consultation may greatly reduce repair time. If the ECM needs to be replaced, see Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP