Alternator Control Circuit Troubleshooting

NOTE: Do this troubleshooting if, in step 4 of the alternator and the regulator circuit troubleshooting (see step 4 on Alternator and Regulator Circuit Troubleshooting , the battery voltage is less than 13.5 V.

Connect the Honda Diagnostic System (HDS) to the data link connector (DLC) (see step 2 on GENERAL TROUBLESHOOTING INFORMATION ).
Turn the ignition switch to ON (II).
Make sure the HDS communicates with the vehicle and the powertrain control module (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 & Positive Terminal Of Battery
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there less than 1 V?

YES - Go to step 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 & Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

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

NO - Update the PCM (see PCM UPDATE ) if it does not have the latest software, 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 terminal and connections, 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 & Alternator 4P Connector Terminal No. 2
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES - Replace the alternator (see DRIVE BELT AUTO-TENSIONER AIR BLEEDING ), or repair the alternator (see ALTERNATOR OVERHAUL ).

NO - Repair open in the wire between the alternator and PCM connector terminal C43.