P0108

Diagnostic Chart:

Diagnostic Chart (cont'd):

Wiring Diagram:

Circuit Description
The Manifold Absolute Pressure (MAP) sensor responds to changes in intake manifold pressure (vacuum). A 5 volt reference is applied to the sensor on the 5 volt reference circuit. A variable resistor moves in relation to the manifold pressure and a voltage signal is sent back to the VCM on the MAP signal circuit. This voltage signal varies from 1.0-1.5 volts at closed throttle to 4.0-4.6 volts at wide open throttle (low vacuum). The VCM utilizes the MAP signal and throttle position in order to determine the correct amount of fuel delivered to the engine. This DTC is a type A DTC.


Conditions for Setting the DTC
The following conditions will set the DTC:

^ No TP sensor DTCs are set.
^ Throttle Position is no more than 0.4% when engine speed is no more than 1200 RPM.
^ Or the Throttle Position is no more than 19.9% when engine speed is greater than 1200 RPM.
^ MAP is greater than or equal to 4.34 volts.

Action Taken When the DTC Sets
The VCM turns on the Malfunction Indicator Lamp (MIL) when DTC P0108 is reported and 1 failure has occurred. The VCM substitutes a calculated value for the MAP sensor so acceptable performance is maintained.

Conditions for Clearing the MIL/DTC
The VCM turns the MIL off after 3 consecutive driving trips without a fault condition present. A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 40°F from the start-up coolant temperature and the engine coolant temperature exceeds 160°F during that same ignition cycle) or the scan tool clearing feature has been used.

Diagnostic Aids
Important: The electrical connector must remain securely fastened.

Important: After removing the MAP sensor from the intake manifold, replace the MAP Sensor to intake manifold seal.

An intermittent ground in the MAP signal or the 5 volt reference circuit results in a DTC P1106. With the ignition ON and the engine off, the manifold pressure is equal to atmospheric pressure with the signal voltage high. The VCM uses this information as an indication of the vehicle's altitude. Comparison of this reading with a known good vehicle using the same sensor is a good way to check accuracy of a suspect sensor. Readings should be the same ±0.4 volts. Refer to Intermittents.

Disconnect the sensor from bracket and twist sensor by hand (only) to check for intermittent connections. Output changes greater than 0.1 volts indicates a bad connector or connection. If OK, replace sensor.

Test Description
The numbers below refer to the step numbers on the diagnostic table.

Important: Be sure to use the same diagnostic equipment for all measurements.

5. This step checks for a short to voltage on the 5V reference circuit.
6. This step checks the integrity of the MAP sensor ground circuit.
10. VCM pins GR12 and GR27 are spliced together inside the VCM. This step isolates the two pins from one another.