Circuit Description

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.

Conditions required to set DTC are:

• PCM detects an out of tolerance condition on 5-volt reference "B"circuit.
• Condition present for longer than 10 seconds.