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.

Remove the engine compartment covers (see ENGINE COMPARTMENT COVER REPLACEMENT )
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), or press the engine start/stop button to select the ON mode
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 And Positive Terminal Of Battery
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there less than 1 V?

YES -Go to step 12

NO -Go to step 9
Jump the SCS line with the HDS, then turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode
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 short to ground 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 ECM/PCM UPDATE ), or substitute a known-good PCM (see SUBSTITUTING THE ECM/PCM ), then recheck If the symptom/indication goes away with a known-good PCM, replace the original PCM (see ECM/PCM REPLACEMENT )
Jump the SCS line with the HDS, then turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode
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 open in the wire between alternator 4P connector terminal No 2 and PCM connector terminal C43
Install the engine compartment covers (see ENGINE COMPARTMENT COVER REPLACEMENT )