Diagnostic Aids

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

If all 3 sensors tied to 5-volt reference circuit set low sensor voltage DTCs, a short to ground probably exists on 5-volt reference circuit.

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

MAP sensor circuit contains it's own 5-volt reference supply. ECT and IAT circuits are on their own 5-volt reference supply also.

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