The manifold absolute pressure (MAP) sensor is a transducer that varies resistance according to changes in the intake manifold pressure (vacuum). The ECM measures the signal voltage from the MAP sensor, which is a reduced value of the ECM 5-volt reference. The voltage ranges from 1.0-1.5 volts at idle (low pressure/high vacuum), in park at normal operating temperature with all accessories Off, to 4.0-4.8 volts at wide open throttle (high pressure/low vacuum). DTC P0108 sets when the MAP sensor signal voltage at the ECM is above the calibrated voltage value.

DTC P0108 will set if the MAP sensor signal voltage is greater than 4.88 (90 kPa) when:

DTC P0108 diagnostic runs continuously with once the above conditions have been met.

P0108 is a type B DTC.

To locate an intermittent problem, use the scan tool to monitor the MAP SENSOR voltage with the engine running. Wiggling the wires while watching for a change in the MAP SENSOR voltage, may locate the area where an open or short to voltage in the wiring could lie.

With the ignition On and the engine Off, the MAP reading should be the same as the barometric pressure reading. Compare it to the reading of a known good vehicle with the same sensor to determine the accuracy of the suspect sensor. Readings should be less than, but not greater than 0.40 volts.

Circuits 416 (CMP/EGR/MAF/MAP sensor), circuit 2709 (AC pressure/fuel tank pressure sensor) and circuit 1164 (APP sensor 1) share the same 5-volt reference supply (5 volt Ref-A).

The CMP/ECT/IAT/EGR/MAF/MAP/TP1/TP2 sensors share the same sensor return circuit 652.

Important: Inaccurate readings will occur if resistance measurements are taken on a MAP sensor. The MAP sensor contains an internal amplifier circuit that requires applied voltage to function properly.

Important: A direct short to voltage on circuit 652 may cause internal damage to the ECM ground trace, or open the sensor element in the ECT, IAT, and/or MAP sensors.