793F Series AC Off-Highway Truck/Tractor Braking System Caterpillar

Illustration 1	g06016284
Simplified Schematic for CID 1674 (Solenoid Return #1)

This diagnostic code is associated with the "Solenoid Return #1" circuit. FMI 05 indicates that the current in the return circuit for the Automatic Retarder Control (ARC) solenoids is below normal.

Conditions that can cause this diagnostic code to be activated are listed below:

• The return circuit for one or more of the ARC solenoids is open.

• Both ARC solenoids have internal open circuits at the same time. This situation is less common.

• The ECM has failed. ECM failure is unlikely.

Note: Before performing this procedure, inspect the harness connectors that are involved in the circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean, secure and in good condition. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure.

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

Test Step 1. CHECK THE SOLENOIDS

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

2. Disconnect the ARC solenoids detailed in illustration 1.

3. At each solenoid, measure the resistance of the solenoid coil between contact 1 and contact 2.

Expected Result:

At 25° C (77° F), the rated resistance measurement across each ARC solenoid coil is 4.7 ohms to 5.3 ohms.

Results:

• OK - Each ARC solenoid coil resistance measurement is within the rated specification. Proceed to Test Step 2.

• NOT OK - The resistance coil measurement for one or more of the ARC solenoids is greater than the rated specification. An open is in one or both of the solenoid coils.

  Repair: Replace the faulty solenoid or solenoids.One faulty solenoid may not cause the Brake ECM to activate the CID 1674 FMI 05 diagnostic code. After the solenoid is replaced, verify that the CID 1674 FMI 05 diagnostic code is still active. If the diagnostic code is still active, perform the next test step.

  STOP

Test Step 2. CHECK THE ENERGIZE CIRCUITS OF THE SOLENOID

Note: The purpose of this step of the test is to verify the integrity of the energize circuits. The energize circuits are used to check the condition of the return circuit in the next test step. A problem in one of the energize solenoid circuit would likely not cause the Brake ECM to activate the CID 1674 FMI 05 diagnostic code. The ECM will activate a specific diagnostic code for a problem in the energize circuit for any of the solenoids.

The disconnect switch and the key start switch remain in the OFF position. Both of the solenoids remain disconnected from the machine harness.

1. At the machine harness connectors for the solenoids, connect a jumper wire between contact 1 on an ARC solenoid. Connect the other end of the jumper wire to contact 1 of the second ARC solenoid.

2. Disconnect the J1 harness connector from the Brake ECM.

3. Measure the resistance of the two solenoids connected by the jumper wire.

Expected Result:

The resistance measurement is less than 5 ohms between the two energize circuits of the solenoids.

Results:

• OK - The resistance measurement is less than 5 ohms between the two energize circuits of the solenoid. The energize circuits for the solenoids are correct. Proceed to Test Step 3.

• NOT OK - The resistance measurement for the energize circuits of the solenoid is greater than 5 ohms. There is a problem in one or both of the ARC solenoid energize circuits.

  Repair: A resistance measurement that is greater than 5 ohms but less than 5000 ohms could indicate that one of the connection points in the circuit is not an open connection but not a good connection. A resistance measurement that is greater than 5000 ohms could indicate that an open is present in the circuit.
  Check each of the energize circuits of the solenoids for continuity to determine the circuit that has an open connection or a poor connection.
  Refer to the complete Electrical System Schematic of your machine. Check all the connectors that are in the suspected circuit. Ensure that all connections are clean, secured and in good condition.
  Repair or replace the machine harness.

  STOP

Test Step 3. CHECK THE RETURN CIRCUIT FOR THE SOLENOID

The disconnect switch and the key start switch remain in the OFF position. Each of the solenoids and the Brake ECM J1 connector remain disconnected from the machine harness.

1. At the machine harness connector for one of the ARC solenoids, place a jumper wire between contact 1 and return contact 2.

2. At the machine harness J1 connector for the Brake ECM, measure the resistance between the energize circuit for the ARC solenoid and the return contact.

3. Repeat the process above for the other ARC solenoid detailed in the illustration 1.

Expected Result:

Each of the resistance measurements is less than 5.0 ohms.

Results:

• OK - Each of the resistance measurements is less than 5.0 ohms. The resistance measurement is indicating that the "Solenoid Return #1" circuit is not causing the problem. Proceed to Test Step 4.

• NOT OK - One or more of the resistance measurements are greater than 5.0 ohms. the "Solenoid Return #1" circuit is not correct.

  Repair: A resistance measurement that is greater than 5 ohms but less than 5000 ohms could indicate that one of the connection points in the circuit is not an open connection but not a good connection. A resistance measurement that is greater than 5000 ohms could indicate that an open is present in the circuit.
  If the problem exists for one or more of the solenoids look for a splice in the circuit. The likely problem is in the section of the return circuit of the solenoid that is between the splice of the wiring harness and the solenoid.
  Refer to the complete Electrical System Schematic of your machine. Check all connectors that are in the suspected section of the "solenoid 1 return" circuit. Ensure that all connections are clean, secure and in good condition.
  Repair or replace the machine harness.

  STOP

Test Step 4. CHECK THE STATUS OF THE DIAGNOSTIC CODE

Reference:
Testing and Adjusting, "Electrical Connector - Inspect"

1. Inspect the harness connectors. Clean the contacts of the harness connectors. Check the wires for damage to the insulation that is caused by excessive heat, battery acid, or chafing.

2. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the sensor circuit.

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

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

5. Operate the machine.

6. Check the status of the CID 1674 FMI 05 diagnostic code.

Expected Result:

The CID 1674 FMI 05 diagnostic code is not active.

Results:

• OK - The CID 1674 FMI 05 diagnostic code is not active. The diagnostic code does not currently exist.

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

  STOP

• NOT OK - The CID 1674 FMI 05 diagnostic code is still active. The diagnostic code has not been corrected.

  Repair: Check the circuit again. Use the Cat Electronic Technician (ET) service tool to perform a wiggle test on the machine wiring harness. The wiggle test can detect momentary or intermittent shorts or opens in the machine wiring harness.Verify that all possible causes of the diagnostic code have been investigated. If the cause of the failure is not found, contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM must be replaced, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP