One of the three PCM 5 volt reference circuits provide reference voltage to the A/C pressure sensor, fuel tank pressure sensor, and throttle position (TP) sensor. The current for each 5 volt reference circuit flows through the sensor to ground, which is provided internal to the PCM. The PCM regulates the 5 volt reference voltage to 5 volts under most normal operating conditions. This is necessary for accurate sensor information.

To locate an intermittent problem, use the scan tool to monitor any of the sensors tied to the 5 volt reference circuit (A/C pressure sensor, fuel tank pressure sensor, and TP sensor). Wiggling the wires while watching for a change in any one of the sensors may locate the area where a short to ground or short to voltage on the 5 volt reference circuit could lie.

If all three sensors tied to the 5 volt reference circuit set low sensor voltage DTCs, a short to ground probably exists on the 5 volt reference circuit.

If DTC P0453 and P0105 are set, a short to voltage on the 5 volt reference circuit may exist. If a short to voltage occurs on the 5 volt reference circuit, the scan tool will display TP ANGLE between 20-30 percent with the throttle plate closed, A/C HIGH SIDE PRESSURE will read over 2.4 volts with the A/C OFF, and FUEL TANK PRESSURE will read over 4 volts.

Driveability conditions will exist if a short on the 5 volt reference circuit is present.

Important: Inaccurate readings will occur if resistance measurements are taken on the A/C pressure sensor or fuel tank pressure sensor. These sensors contain an internal amplifier circuit that requires applied voltage to function properly.

The ECT and IAT share one 5 volt reference supply. The MAP sensor uses a separate 5 volt reference supply and is not shared with any of the sensors.