Alternator FR Signal Circuit Troubleshooting

1.Disconnect the alternator 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 alternator 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 alternator 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 alternator 4P connector.

12.Connect alternator 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 alternator.n


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


NO - Substitute a known-good ECM/PCM and recheck. If symptom/indication goes away, replace the original  ECM/ PCM.n