For 1990-2009 cars

### Circuit Description

The 5 volt reference circuit provides a signal voltage to the linear EGR, MAP sensor, and TP sensor. The return line is grounded through the PCM. DTC P1635 detects a short to ground in any of the 3, 5 volt reference circuits or inside the PCM.

### Conditions for Setting the DTC

Important: The 5 volt reference is monitored whenever the ignition is ON.

DTC P1635 will set if the 5 volt reference signal is below 3.5 volts or above 5.5 volts. This voltage is monitored internally by the PCM.

### Diagnostic Aids

If DTCs P0563, P0108, P1106, P0452, P0453, P1122, or P0122 are set, a short to B+ on the 5 volt reference circuit is probable. If the short exists while attempting to diagnose, PDT communications will be lost and driveability conditions will exist.