Com Circuit Inspection

■ Check waveform 

1. IG "OFF". Disconnect GDS.
2. Connect probe to COM terminal to check control waveform by using oscilloscope function.
3. ENG running monitor signal waveform.

   Specification:  refer to SIGNAL WAVEFORM & DATA 

4. Is the measured waveform within specification?

   YES 

   • Go to "Check Open in harness" below.

   NO 

   • Go to "Check Short in harness" below.

■ Check Open in harness 

1. IG "OFF". Disconnect Alternator and PCM connector
2. Measure resistant between com terminal of alternator and PCM harness connector.

   Specification:  Below 1Ω

3. Is the measured resistance within specification?

   YES 

   • Substitute with a known - good PCM and check for proper operation. If the problem is corrected, replace PCM and go to "VERIFICATION OF VEHICLE REPAIR " procedure.

   NO 

   • Repair open in harness. Go to "VERIFICATION OF VEHICLE REPAIR " procedure.

■ Check Short in harness 

1. IG "OFF". Disconnect Alternator and PCM connector
2. Measure the resistance between com terminal of the alternator harness connector and chassis ground.
3. IG "ON" and measure the voltage between com terminal of the alternator harness connector and chassis ground.

   Specification:  Approx. below 1Ω, Approx. 0V

4. Is the measured resistance and voltage within specification?

   YES 

   • Substitute with a known - good PCM and check for proper operation. If the problem is corrected, replace PCM and go to "VERIFICATION OF VEHICLE REPAIR " procedure.

   NO 

   • Repair short in harness. Go to "VERIFICATION OF VEHICLE REPAIR " procedure.