P0108

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

The Manifold Absolute Pressure (MAP) sensor responds to changes in the 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 4.0-4.5 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.

CONDITIONS FOR SETTING THE DTC

The following conditions will set the DTC:

^ No TP sensor DTCs

^ Throttle Position is no more than 0.4% when engine speed is less than 1200 RPM, or the Throttle Position is no more than 20% when engine speed is greater than 1200 RPM

^ The MAP is greater than or equal to 4.9 V

ACTION TAKEN WHEN THE DTC SETS

The VCM turns ON the MIL when DTC P0108 is reported and 1 failure has occurred. The VCM substitutes a calculated value for the MAP sensor value so an acceptable driving condition is maintained.

CONDITIONS FOR CLEARING THE MIL/DTC

^ The VCM turns the MIL OFF after 3 consecutive drive trips when the test has Run and Passed and not Failed.

^ A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant temperature exceeds 70°C (160°F) during the same ignition cycle).

^ Use the scan tool Clear Information function.

^ Disconnect the VCM battery feed for 30 seconds.

DIAGNOSTIC AIDS

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 within 0.4 volts.

Refer to Symptoms. Testing and Inspection

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.

Remove the MAP sensor. Twist sensor by hand (only) to check for intermittent connections. Output changes greater than 0.1 volt 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 5 volt reference circuit.

7. This step checks the integrity of the MAP sensor ground circuit.

11. The VCM terminals CLR 12 and CLR 27 are spliced together inside the VCM. When checking the 5 volt reference for a short to ground, both the 5 volt reference circuits and all of the components on the 5 V reference circuits must also be checked.