Alternator FR Signal Circuit Troubleshooting

Alternator FR Signal Circuit Troubleshooting

1. Start the engine, and let it idle.

2. Monitor the ALTERNATOR in the DATA LIST with the HDS.

3. Check if the indicated percentage varies when the headlight switch is turned on.

Does the percentage vary?
YES - The alternator FR signal circuit is OK.

NO - Go to step 4.


4. Turn the headlight switch off, and turn the ignition switch to LOCK (0).

5. Disconnect the alternator 4P connector.

6. Turn the ignition switch to ON (II).

7. Measure the voltage between ECM connector terminals A9 and B13.

Is there about 5 V?
YES - Go to step 8.

NO - Go to step 13.






8. Turn the ignition switch to LOCK (0).

9. Jump the SCS line with the HDS.

10. Disconnect ECM connector B (24P).

11. Connect alternator 4P connector terminal No. 4 to body ground with a jumper wire.






12. Check for continuity between body ground and ECM connector terminal B13.

Is there continuity?
YES - Test the alternator. Alternator and Regulator Circuit Troubleshooting

NO - Repair open in the wire between the ECM (B13) and the alternator.






13. Turn the ignition switch to LOCK (0).

14. Jump the SCS line with the HDS.

15. Disconnect ECM connector B (24P).

16. Check for continuity between body ground and ECM connector terminal B13.

Is there continuity?
YES - Repair short in the wire between the ECM (B13) and the alternator.

NO - Update the ECM if it does not have the latest software, ECM Update or substitute a known-good ECM, Initial Inspection and Diagnostic Overview then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM. Service and Repair