5-VOLT REFERENCE "B" CIRCUIT
PCM uses 5-volt reference "B" circuit as a sensor feed for
A/C refrigerant pressure sensor. PCM monitors voltage on this circuit.
If PCM senses voltage out of tolerance, DTC P1639 sets.
You likely won't notice any drivability problems.
- PCM detects an out of tolerance condition on 5-volt reference
- Check for faulty connections or damaged harness on AC pressure sensor.
- Check for shorts in AC pressure sensor wires
- Replace A/C pressure sensor.