## Alternator FR Signal Circuit Troubleshooting

1. | Start the engine. and let it idle.

2. | Check the ALTERNATOR in the DATA LIST with the HDS.

3. | Check if the indicated percentage varies when the lighting switch is ON. Does the percentage vary? YES - The alternator signal circuit is OK.n NO - Go to 4.

4. | Turn the lighting switch and ignition switch OFF, and wait 10 seconds.

5. | Disconect the alternator 2P connector.

6. | Connect the ECM test harness and the test pin box between the ECM and connector.

7. | Turn the ignition switch ON (II).

8. | Measure voltage between test pin box terminals No. 48 and No. 98. Is there about 5 V? YES - Go to 9. NO - Go to 13.

9. | Turn the ignition switch OFF, and wait 10 seconds.

10. | Disconnect the ECM test harness from the ECM.

11. | Connect the alternator 2P connector terminals No. 2 to body ground with a jumper wire.

12. | Check for continuity between test pin box terminal No. 48 and body ground. Is there continuity? YES - Test the alternator.n NO - Repair open in the wire between the ECM connector No. 3 terminal No. 19 (test pin box terminal No. 48) and the alternator.n

13. | Turn the ignition switch OFF, and wait 10 seconds.

14. | Disconnect the ECM test harness from the ECM.

15. | Check for the continuity between test pin box terminal No. 48 and body ground. Is there continuity? YES - Repair short in the wire between the ECM connector No. 3 terminal No. 19 (test pin box terminal No. 48) and the alternator.n NO - Substitute a known-good ECM and recheck. If symptom/indication goes away, replace the original ECM.n