P0108

DTC P0108 Diagnostic Chart:

MAP Sensor Circuit:

Circuit Description
The Manifold Absolute Pressure (MAP) sensor responds to changes in manifold pressure (vacuum). The VCM receives this information as a signal voltage that will vary from 1-1.5 volts at closed throttle (idle) and 4-4.6 volts at Wide Open Throttle (WOT) (low vacuum).

If the MAP sensor fails, the VCM will substitute a fixed MAP value and use the Throttle Position (TP) sensor to control fuel delivery.

DTC P0108 Will Set When
MAP is greater than 68 kPa, TP is less than 2%, engine speed is greater than 700 RPM for 5 seconds.

Action Taken (VCM will default to)
MAP will default to 90.8 kPa.

DTC P0108 Will Clear When
Conditions for fault are no longer present and Tech 1 clear DTCs function is used or 50 ignition switch keycycles have passed with no further faults or ignition switch is turned "OFF" and Fuse #9 (ECM B) fuse is removed for 10 seconds.

DTC Chart Test Description
Number(s) below refer to circled number(s) on the diagnostic chart.

1. Rough, unstable or incorrect idle and manifold vacuum less than 15" must be corrected before using this chart. See "Symptoms".

2. This step simulates conditions for a DTC P0108. If the VCM recognizes the change, the VCM and CKT 474 and CKT 432 are OK.

Diagnostic Aids
With the ignition "ON" and the engine stopped, the manifold pressure is equal to atmospheric pressure with the signal voltage being high. This information is used by the VCM as an indication of vehicle 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 ± .4 volt.

A DTC P0108 will set if CKT 455 is open or if CKT 432 is shorted to voltage or to CKT 474.

If DTC P0108 is intermittent, refer to Symptoms. Testing and Inspection
^ Check all connections.
^ Disconnect sensor from bracket and twist sensor connections. Output changes greater than .1 volt indicates a bad connector or connection. If OK, replace sensor.

NOTICE: Electrical connector must remain securely fastened.

^ Refer to "MAP Output Check" for further diagnosis. MAP Sensor Output Diagnosis