Alternator Control Circuit Troubleshooting
- Connect the Honda Diagnostic System (HDS) to the data link connector (DLC), and check for DTCs (see step 2 HOW TO USE THE HDS (HONDA DIAGNOSTIC SYSTEM) ). If a DTC is present, diagnose and repair the cause before continuing with this test.
- Disconnect the alternator 4P connector from the alternator.
- Start the engine, and turn on the headlights to high beam.
- Measure the voltage between alternator 4P connector terminal No. 2 and the positive terminal of the battery.Fig 1: Measuring Voltage Between Alternator 4P Connector Terminal No 2 And Positive Terminal Of Battery
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Is there 1 V or less?
YES - Go to step 5.
NO - Go to step 8.
- Jump the SCS line with the HDS, then turn the ignition switch OFF.NOTE: This step must be done to protect the powertrain control module (PCM) from damage.
- Disconnect PCM connector C (44P).
- Check for continuity between PCM connector terminal C38 and body ground.
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Is there continuity?
YES - Repair short in the wire between the alternator and PCM.
NO - Update the PCM if it does not have the latest software (see PCM UPDATING AND SUBSTITUTION FOR TESTING ), or substitute a known-good PCM (see HOW TO SUBSTITUTE THE PCM ), then recheck. If the symptom/indication goes away with a known-good PCM, replace the original PCM (see HOW TO REMOVE THE PCM FOR TESTING ).
- Jump the SCS line with the HDS, then turn the ignition switch OFF.NOTE: This step must be done to protect the powertrain control module (PCM) from damage.
- Disconnect PCM connector C (44P).
- Check for continuity between PCM connector terminal C38 and alternator 4P connector terminal No. 2.Fig 3: Checking Continuity Between PCM Connector Terminal C38 And Alternator 4P Connector Terminal No 2
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
YES - Replace the alternator (see ALTERNATOR REPLACEMENT ) or repair the alternator (see ALTERNATOR OVERHAUL ).
NO - Repair an open in the wire between the alternator and PCM.