Alternator Control Circuit Troubleshooting

NOTE: Do this troubleshooting if, in step 4 of the Alternator and Regulator Circuit Troubleshooting (see ALTERNATOR AND REGULATOR CIRCUIT TROUBLESHOOTING ), the battery voltage is less than 13.5 V.

Connect the HDS to the DLC (see step 2 on HOW TO USE THE HDS (HONDA DIAGNOSTIC SYSTEM) ).
Turn the ignition switch to ON (II).
Make sure the HDS communicates with the vehicle and the PCM. If it does not communicate, troubleshoot the DLC circuit (see DLC CIRCUIT TROUBLESHOOTING ).
Check for DTCs (see GENERAL TROUBLESHOOTING INFORMATION ). If a DTC is present, diagnose and repair the cause before continuing with this test.
Disconnect the alternator 4P connector.
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
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there less than 1 V?

YES -Go to step 11 11.

NO -Go to step 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 PCM from damage.
Disconnect PCM connector C (49P).
Check for continuity between PCM connector terminal C43 and body ground.

Fig 2: Checking Continuity Between PCM Connector Terminal C43 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Repair a short in the wire between alternator 4P connector terminal No. 2 and PCM connector terminal C43.

NO -Update the PCM if it does not have the latest software (see PCM UPDATE ), or substitute a known-good PCM (see SUBSTITUTING THE PCM ), then recheck. If the symptom/indication goes away with a known-good PCM, replace the original PCM (see PCM REPLACEMENT ).
Jump the SCS line with the HDS, then turn the ignition switch to LOCK (0).
NOTE: This step must be done to protect the PCM from damage.
Disconnect PCM connector C (49P).
Check for loose terminals and connectors, then check for continuity between PCM connector terminal C43 and alternator 4P connector terminal No. 2.

Fig 3: Checking Continuity Between PCM Connector Terminal C43 And Alternator 4P Connector Terminal No. 2

Courtesy 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 PCM connector terminal C43.