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Alternator Control Circuit Troubleshooting

NOTE: Do this troubleshooting if, in step  5 of the ALTERNATOR AND REGULATOR CIRCUIT TROUBLESHOOTING  , the battery voltage is less than 13.5 V.
  1. Connect the HDS to the DLC (see step 2 under HOW TO USE THE HDS (HONDA DIAGNOSTIC SYSTEM) ).
  2. Turn the ignition switch to ON (II).
  3. Make sure the HDS communicates with the vehicle and the ECM/PCM. If it does not communicate, troubleshoot the DLC circuit (see DLC CIRCUIT TROUBLESHOOTING ).
  4. Check for DTCs (see GENERAL TROUBLESHOOTING INFORMATION ). If a DTC is present, diagnose and repair the cause before continuing with this test.
  5. Disconnect the alternator 4P connector.
  6. Start the engine, and turn on the headlights to high beam.
  7. Measure the voltage between alternator 4P connector terminal No. 2 and the positive terminal of the battery.
    Fig 1: Measuring Voltage Between Connector Terminal And Battery
    G07340703Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there less than 1 V? 

    YES  -Go to step  11.

    NO  -Go to step 8.

  8. 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/PCM from damage.
  9. Disconnect ECM/PCM connector B (49P).
  10. Check for continuity between ECM/PCM connector terminal B45 and body ground.
    Fig 2: Checking Continuity Between ECM/PCM Connector Terminal And Body Ground
    G07340704Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  -Repair a short to ground in the wire between alternator 4P connector terminal No. 2 and ECM/PCM connector terminal B45.

    NO  -Update the ECM/PCM if it does not have the latest software (see ECM/PCM UPDATE ), or substitute a known-good ECM/PCM (see SUBSTITUTING THE ECM/PCM ), then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM (see ECM/PCM REPLACEMENT ).

  11. 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/PCM from damage.
  12. Disconnect ECM/PCM connector B (49P).
  13. Check for loose terminal and connectors, then check for continuity between ECM/PCM connector terminal B45 and alternator 4P connector terminal No. 2.
    Fig 3: Checking Continuity Between ECM/PCM Connector Terminal B45 And Alternator 4P Connector Terminal No. 2
    G07340705Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  -Replace the alternator (see ALTERNATOR REMOVAL AND INSTALLATION  ), or repair the alternator (see ALTERNATOR OVERHAUL  ).

    NO  -Repair an open in the wire between alternator 4P connector terminal No. 2 and ECM/PCM connector terminal B45.

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