July 1: So it begins. Don't worry, this is not in the correct legal jurisdiction!

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/range, DTC P1639 sets.

Conditions required to set DTC are:

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