The manifold absolute pressure (MAP) sensor is a transducer that varies resistance according to changes in intake manifold pressure (vacuum). The PCM measures the signal voltage from the MAP sensor, which is a reduced value of the PCM 5 volt reference. The voltage ranges from 1-1.5 volts at idle (low pressure/high vacuum) to 4.5-4.8 volts at wide open throttle (high pressure/low vacuum). DTC P0108 sets when the MAP sensor signal voltage at the PCM is above the calibrated voltage value.
Conditions for Setting the DTC
DTC P0108 will set if MAP sensor voltage is greater than 3.8 volts when:
| • | The condition exists for longer than 10 seconds. |
| • | Engine run time is greater than 40 seconds. |
| • | The TP angle is less than 12 percent. |
| • | Vehicle speed is NOT present. |
| • | No TP sensor DTCs have been set. |
DTC P0108 diagnostic runs continuously with the engine running.
DTC P0108 is a type B DTC
Diagnostic Aids
To locate an intermittent problem, use the scan tool to monitor MAP sensor voltage with the engine running. Wiggling the wires while watching for a change in MAP sensor voltage, may locate the area where an open or short to voltage in the wiring could lie.
With ignition the 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 within 0.4 volts.
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.
The PCM supplies the MAP sensor with its own separate 5 volt reference source. There are no other external components tied to it.
