DTC P1639: 5-Volt Reference 2 Circuit: Description

The Powertrain Control Module (PCM) uses the 5-volt reference 2 circuit as a sensor feed to the following sensors:

• The AC pressure sensor.
• The Fuel Tank Pressure (FTP) sensor.

The PCM monitors the voltage on the 5-volt reference 2 circuit. If the voltage is out of tolerance, the PCM will set DTC P1639.