COM Circuit Inspection
- Check waveform
- IG "OFF". Disconnect GDS.
- Connect probe to COM terminal to check control waveform by using oscilloscope function.
- With the engine running, monitor signal waveform.
Specification: Refer to SIGNAL WAVEFORM & DATA
- Is the measured waveform within specification?
YES
- Go to "CHECK OPEN IN HARNESS" as follows. (Refer to 2)
NO
- Go to "CHECK SHORT IN HARNESS" as follows. (Refer to 3)
- Check open in harness
- IG "OFF". Disconnect alternator and PCM connector.
- Measure resistance between COM terminal of alternator and PCM harness connector.
Specification: Below 1Ω
- 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
- IG "OFF". Disconnect alternator and PCM connector.
- Measure the resistance between COM terminal of the alternator harness connector and chassis ground.
- IG "ON". Measure the voltage between COM terminal of the alternator harness connector and chassis ground.
Specification: Approx. below 1Ω, Approx. 0V
- 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.