P1639high severityPowertrain
5 Volt Reference 2 Circuit
on 2013 Cadillac ATS 3.6L V6 · RWD
What this code means
The PCM detected that the 5-volt reference B circuit voltage is out of tolerance. This is a separate 5V reference circuit from P1635 and feeds a different set of sensors.
Symptoms
- Check Engine Light
- Engine stalling
- Multiple sensor DTCs
- Poor drivability
- Loss of power
Common causes
- Short to ground in a connected sensor circuit
- Damaged sensor wiring
- Faulty sensor on this reference
- PCM 5V reference driver failure
Diagnostic steps
- Measure 5V reference 2 voltage
- Disconnect sensors one at a time on this circuit
- Inspect wiring for shorts
- Test PCM output
Repair notes
Same diagnostic approach as P1635. Disconnect sensors one at a time to isolate the shorted circuit.
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