AD55B Underground Articulated Truck Power Train Electronic Control System Caterpillar

Illustration 1	g01401948
Schematic of the Powertrain/Chassis ECM supply voltage circuits

This diagnostic code is associated with the machine system voltage that is supplied to the Power Train/Chassis Electronic Control Module (ECM). The FMI 02 means that the ECM has detected that the system voltage is erratic or intermittent. The ECM activates this diagnostic code when the system voltage is not in the range of 18 VDC to 32 VDC for more than a few seconds.

The possible causes of this diagnostic code are listed below:

• A poor system ground circuit connection.

• A poor system voltage supply circuit connection.

• A charging system component has failed.

• The ECM has failed. This is unlikely.

Note: Before performing this procedure, verify that all circuit breakers and fuses in the charging circuit and the ECM system supply circuit are closed. If a problem with a circuit breaker or a fuse is found, correct the problem and verify that this diagnostic code is active before performing this procedure.

Test Step 1. CHECK SYSTEM VOLTAGE AT THE ECM

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

2. At the machine harness connector J1 for the ECM, insert a 7X-1710 Multimeter Probe along the system power supply contacts J1- 31,39,46 and 47 (wires 101-RD). Use the other multimeter probe to make contact to frame ground.

3. Turn the disconnect switch to the ON position.

4. Start the engine and run the engine at half throttle.

5. Measure the voltage between contacts J1-31,39,46 and 47 (wires 101-RD) and frame ground.

6. While observing the multimeter voltage measurement, wiggle the machine harness connectors for the ECM. Gently pull on the wires and gently move the wires around.

7. At the J1 harness connector for the ECM, insert the 7X-1710 Multimeter Probe that was used for the frame ground contact along the system power supply battery (-) contacts J1-13,23,56,57 and 70 (wires 202-BK).

8. Measure the voltage between contact J1-31 (wire 101-RD) and contacts J1-13,23,56,57 and 70 (wires 202-BK).

9. While observing the multimeter voltage measurement, wiggle the machine harness connectors for the ECM. Gently pull on the wires and move the wires around.

Expected Result:

Each voltage measurement is approximately the same and are in the range of 18 VDC to 32 VDC at all times during the manipulation of the harness and connectors.

Results:

• YES - Each voltage measurement is approximately the same and are in the range of 18 VDC to 32 VDC. The system voltage is correct at all times during the manipulation of the harness and connectors. Proceed to Test Step 6.

• NO - The voltage measurements are approximately the same, however the voltage measurements are unstable. The voltage measurements are showing a large amount of variation. The manipulation of the machine harness and connectors does not affect the measurement. Proceed to Test Step 4.

• NO - The measurement from the +battery contacts to frame ground are stable and are in the range of 18 VDC to 32 VDC, however, the measurement between the ECM +battery contact and the ECM (-) battery contacts are not stable or in the correct range at all times. Proceed to Test Step 2.

Test Step 2. CHECK THE GROUND CIRCUITS

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

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

3. At the machine harness connector J1 for the ECM, measure the resistance between each of the five (5) battery (-) contacts and frame ground. The contacts for the battery (-) connections are illustrated in the connection diagram at the beginning of this procedure.

Expected Result:

Each resistance measurement is less than 5 ohms.

Results:

• YES - Each resistance measurement is less than 5 ohms. The ground circuit is correct. Proceed to Test Step 3.

• NO - One or more of the resistance measurements is greater than 5 ohms. There is an open circuit or a poor connection in the ground circuit.

  Repair: The open or a possible poor connection is in the ECM ground circuit (wire 202-BK) in the machine harness. Refer to the complete machine Electrical System Schematic for this machine. Check the rear frame ground connection points where the wire 202-BK is connected. Ensure that the ground connection is clean, that the ground connection is tight and that the ground connection is in good condition. Check all of the connectors and splice points that are in the ground circuit. Ensure that all connections are clean, that all connections are secure and that all connections are in good condition. Repair the machine harness or replace the machine harness.

  STOP

Test Step 3. CHECK THE SUPPLY CIRCUITS

The key start switch and the disconnect switch remain in the OFF position. The machine harness connector J1 remains disconnected from the ECM.

1. At the machine harness connector J1 for the ECM, using a length of spare wire, measure the resistance between the alternator "B" terminal (wire - OR) to each of the four (4) battery (+) contacts that are connected to the machine harness connector J1. The contacts for the four (4) battery (+) connections are illustrated in the connection diagram at the beginning of this procedure.

Expected Result:

Each resistance measurement is less than 5 ohms.

Results:

• YES - Each resistance measurement is less than 5 ohms. The supply circuit is correct. Reconnect the machine harness connector J1 to the ECM before proceeding to the next test step. Proceed to Test Step 4.

• NO - One or more of the resistance measurements is greater than 5 ohms. There is an open circuit or a poor connection in the supply circuit.

  Repair: The open or a possible poor connection is in the ECM system voltage supply circuit (wire 101-RD) in the machine harness. Verify that there are no open circuit breakers or fuses in the circuit. Refer to the complete Electrical System Schematic for this machine. Check all of the connectors and splice points that are in the supply circuit. Ensure that all connections are clean, that all connections are secure and that all connections are in good condition. Repair the machine harness or replace the machine harness.

  STOP

Test Step 4. CHECK THE ALTERNATOR CURRENT OUTPUT

1. Before performing this test step, partially discharge the batteries. This can be done by cranking the engine for approximately 30 seconds without starting the engine. This can also be done by turning on the lights for about 10 minutes without running the engine.

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

3. At the alternator, connect multimeter probes between the alternator "B" terminal (wire - OR) and the alternator case (frame ground).

4. Connect a clamp on 8T-0900 AC/DC Clamp-on Ammeter or equivalent ammeter around the OR output wire .

5. Turn the disconnect switch to the ON position.

6. Start the engine.

7. Run the engine at approximately half throttle.

8. Immediately check the output current of the alternator.

Expected Result:

The output current of the alternator at half throttle is approximately 40 - 50 amps, approximately half the alternator full current output rating (95 Amps). The current measurement is stable.

Results:

• YES - The output current of the alternator at half throttle is approximately 40 - 50 amps and is stable. Proceed to Test Step 5.

• NO - The output current of the alternator at half throttle is not stable. The measurement is showing a large variation of current values. The current output of the alternator is not correct.

  Repair: Repair or Replace the alternator.

  STOP

Test Step 5. CHECK THE ALTERNATOR VOLTAGE OUTPUT

The multimeter and the ammeter are still connected. The engine is running.

1. Run the engine for approximately 10 minutes at half throttle.

2. Check the voltage at the alternator output terminal "B".

Expected Result:

The voltage measurement is 28 ± 1 VDC. There is little variation or no variation in the voltage measurement.

Results:

• YES - The voltage measurement is 28 ± 1 VDC. The voltage is stable. The voltage output of the alternator is correct. Proceed to Test Step 6.

• NO - The voltage is not stable. There is a large variation in the measured voltage. The voltage output is not correct.

  Repair: Repair or replace the alternator.

  STOP

Test Step 6. CHECK THE STATUS OF THE DIAGNOSTIC CODE

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

2. Reconnect any harness connectors that were disconnected and checked.

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

4. Operate the machine.

5. Determine if the CID 0168 FMI 02 diagnostic code is active.

Expected Result:

The CID CID 0168 FMI 02 diagnostic code is active.

Results:

• YES - The CID 0168 FMI 02 diagnostic code is active.

  Repair: Perform this procedure again. Verify that the alternator measurements are correct. Verify that the system voltage circuit connections are in good condition and verify that the system voltage circuit connections are tight.If the problem remains and no cause can be found, the ECM may have failed. It is unlikely that the ECM has failed. Verify that all possible causes of the diagnostic code have been investigated. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, replace the ECM. See Systems Operation, Troubleshooting, Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP

• NO - The CID 0168 FMI 02 code is not active. The problem 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