Alternator FR Signal Circuit Troubleshooting
- Disconnect the alternator 4P connector from the alternator.
- Turn the ignition switch ON (II).
- Measure voltage between ECM connector terminals A24 and B13.
- Is there about 5 V?
- YES:
Go to step 4.
- NO:
Go to step 13.
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- Turn the ignition switch OFF.
- Reconnect the alternator 4P connector.
- Start the engine. Hold the engine at 3,000 RPM with no load (in neutral) until the radiator fan comes on, then let it idle.
- Measure voltage between ECM 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.
- NO:
Go to step 8.
- Turn the ignition switch OFF.
- Disconnect ECM connector B (24P).
- Disconnect the alternator 4P connector.
- Connect alternator 4P connector terminal No. 4 to body ground with a jumper wire.
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- Check for continuity between body ground and ECM connector terminal B13.
- Is there continuity?
- YES:
Test the alternator (see CHARGING SYSTEM
).
- NO:
Repair open in the wire between the ECM (B13) and the alternator.
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- Turn the ignition switch OFF.
- Disconnect ECM connector B (24P).
- 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, or substitute a known-good ECM, then recheck (see ECM UPDATING AND SUBSTITUTION FOR TESTING
). If the symptom/indication goes away with a known-good ECM, replace the original ECM.
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