## Alternator FR Signal Circuit Troubleshooting

1. | Disconnect the ALT 4P connector.

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

3. | Measure voltage between ECM/PCM connector terminals A24 and B13. Is there about 5 V? YES - Go to 4. NO - Go to 14.

4. | Turn the ignition switch OFF.

5. | Reconnect the ALT 4P connector.

6. | Start the engine. Hold the engine at 3,000 rpm (min-1) with no load (in Park or neutral) until the radiator fan comes on, then let it idle.

7. | Measure voltage between ECM/PCM connector terminals A24 and B13. Does the voltage decrease when the headlights and rear window defogger are turned on? YES - The ALT FR signal is OK.n NO - Go to 8.

8. | Turn the ignition switch OFF.

9. | Disconnect the negative cable from the battery.

10. | Disconnect ECM/PCM connector B (24P).

11. | Disconnect the ALT 4P connector.

12. | Connect the ALT 4P connector terminal No. 4 and body ground with a jumper wire.

13. | Check for continuity between body ground and ECM/PCM connector terminal B13. Is there continuity? YES - Test the ALT.n NO - Repair open in the wire between the ECM/PCM (B13) and the ALT.n

14. | Turn the ignition switch OFF.

15. | Disconnect the negative cable from the battery.

16. | Disconnect ECM/PCM connector B (24P).

17. | Check for continuity between body ground and ECM/PCM connector terminal B13. Is there continuity? YES - Repair short in the wire between the ECM/ PCM (B13) and the ALT.n NO - Substitute a known-good ECM/PCM and recheck. If symptom/indication goes away, replace the original ECM/ PCM.n