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 4P 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 4P connector terminals No. 4 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