Alternator Control Circuit Troubleshooting
  1. Check for continuity between ECM connector terminal B45 and body ground.
Is there continuity?
YES -
Repair short in the wire between the alternator and the ECM.■
NO -
Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM. ■
  1. Jump the SCS line with the HDS, then turn the ignition switch to LOCK (0).
    NOTE: This step must be done to protect the ECM from damage.
  1. Disconnect ECM connector B (49P).