416E, 420E and 430E Backhoe Loaders MID 039 - CID 1251 - FMI 08 Caterpillar

Conditions Which Generate This Code:

Illustration 1	g02103502
Schematic of the "Alternator W" Terminal

This diagnostic code is associated with the alternator. The FMI 08 means that the ECM has determined that the voltage is below normal or shorted low.

The possible causes of this diagnostic code are listed below:

• Mechanical devices have failed.

• Intermittent connections or poor connections

• Mechanical devices are loose.

• The circuit is shorted.

• The ECM has failed. This is unlikely.

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 has been corrected. Ensure that the diagnostic code of CID 1251 FMI 08 is active before performing this procedure.

Note: Use the 146-4080 Digital Multimeter for the measurements in this procedure.

Note: Disconnect the positive battery cable from the positive battery post when making changes to the wiring in the charging system. Reconnect the positive cable to the positive battery post when testing has been completed.

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, that all connections are secure and that all connections are 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.

System Response:

The diagnostic code of CID 1251 FMI 08 will be logged in the internal memory of the machine ECM.

Test Step 1. CHECK FOR BATTERY VOLTAGE AT THE ALTERNATOR

1. Do not disconnect the harness connector from the alternator.

2. At the back of the harness connector for the alternator, insert a 7X-1710 Multimeter Probe along wire 450-YL for the voltage supply.

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

4. Use a 146-4080 Digital Multimeter in order to measure the voltage from the wire terminal, J2-14 (wire 450-YL) and a clean contact (ground) on the tractor frame.

Expected Result:

Battery voltage should be displayed on the 146-4080 Digital Multimeter .

Results:

• OK - Battery voltage is displayed on the 146-4080 Digital Multimeter. Battery voltage is being supplied in order to excite the alternator. Reconnect the J2-14 (wire 450-YL) to the alternator. Proceed to Test Step 3.

• NOT OK - Battery voltage is not displayed on the 146-4080 Digital Multimeter. Battery voltage is not being supplied in order to excite the alternator. Proceed to Test Step 4.

Test Step 2. CHECK THE ALTERNATOR GROUND

1. With a 146-4080 Digital Multimeter, check for continuity from a clean ground point on the case of the alternator and a clean ground point on the tractor frame.

Expected Result:

Continuity exists between the case of the alternator and the tractor frame. (If continuity does not exist, verify that clean areas were used for the 146-4080 Digital Multimeter probes and proceed.)

Results:

• OK - Continuity exists between the case of the alternator and the tractor frame. Proceed to the Test Step3.

• NOT OK - Continuity does not exist between the case of the alternator and the tractor frame.

  Repair: The alternator mounting may be dirty or oily. The alternator mounting may be a painted surface. The hardware for attaching the alternator may be loose or broken. Correct any problems.

  STOP

Test Step 3. CHECK THE ALTERNATOR OUTPUT

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

2. Connect one 7X-1710 Multimeter Probe to the "B+" terminal on the alternator and the other 7X-1710 Multimeter Probe to a clean ground point on the tractor frame.

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

4. Monitor the signal with the 146-4080 Digital Multimeter .

5. Take the alternator through the full operating range of the alternator.

Expected Result:

The voltage output of the alternator should be system voltage.

Results:

• OK - The alternator's signal responds correctly. The alternator is operating correctly. Proceed to Test Step 4.

• NOT OK - The alternator's signal does not respond correctly. The alternator has failed.

  Repair: Either repair the alternator or replace the harness of the alternator.

  STOP

Test Step 4. CHECK THE CIRCUIT FOR CONTINUITY.

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

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

3. At the J2 machine harness connector, measure the resistance from contact J2-14 (wire 450-YL) to contact J1-57 (wire 202-BK).

Expected Result:

The measurement of the resistance should be between 5 ohms and 5000 ohms for each switch position.

Results:

• YES - The resistance is correct for each measurement. Proceed to test step 7.

• NO - The resistance measurement is greater than 5000 ohms for one or both measurements. The harness or the switch has failed. Proceed to test step 5.

Test Step 5. CHECK FOR A SHORT IN THE HARNESS.

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

2. Disconnect the machine harness connectors from the alternator and the ECM.

3. Measure the resistance between contact J2-14 (wire 450-YL) and all contacts that are used in the machine harness connectors for the ECM.

Expected Result:

The resistance is greater than 5000 ohms.

Results:

• OK - The resistance is greater than 5000 ohms. The circuit is correct. Proceed to Test Step 6.

• NOT OK - The resistance is less than 5 ohms. The signal circuit is shorted to another circuit in the harness.

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

  STOP

Test Step 6. CHECK FOR A SHORT IN THE SWITCH

1. Disconnect the switch from the harness.

2. At the J1 machine harness connector, measure the resistance from contact J2-14 and contact J1-57 to all other J1 contacts.

Expected Result:

The resistance measurement should be greater than 5000 ohms for each measurement.

Results:

• OK - The resistance measurement is greater than 5000 ohms for each measurement. Proceed to Test Step 7.

• NOT OK - The resistance measurement is not greater than 5000 ohms for one or more measurements.

  Repair: Replace the switch.

  STOP

Test Step 7. CHECK IF THE DIAGNOSTIC CODE REMAINS

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

2. Reconnect all 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 1251 FMI 08 diagnostic code.

Expected Result:

The CID 1251 FMI 08 diagnostic code is not active.

Results:

• OK - The CID 1251 FMI 08 diagnostic code is not active. The diagnostic code does not exist at this time. The initial diagnostic code was probably caused by a poor connection or a short at one of the connectors that was disconnected and reconnected. Resume normal operation.STOP

• NOT OK - The CID 1251 FMI 08 diagnostic code is active. The diagnostic code has not been corrected. The ECM may have failed.

  Repair: Prior to replacing an ECM, always contact your dealership's Technical Communicator for possible consultation with AVSpare. This consultation may greatly reduce repair time. If the ECM must be replaced, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP