P0108

DTC P0108 Manifold Absolute Pressure (MAP) Sensor Circuit - High Input:

Manifold Absolute Pressure (MAP) Output Check:

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 CKT 474. A variable resistor moves in relation to manifold pressure and a voltage signal is sent back to the Vehicle Control Module-A (VCM-A) on CKT 432. This voltage signal will vary from 1-1.5 volts at closed throttle to 4-4.6 volts at wide open throttle (low vacuum).

The VCM-A utilizes the MAP signal and throttle position to determine the correct amount of fuel delivered to the engine. DTC P0108 is a "A" DTC.

DTC P0108 WILL SET WHEN
^ No Throttle Position (TP) sensor DTC's set.
^ Engine running.
^ Throttle Position at least 0% when engine speed is less than 575.
OR
^ Throttle Position is at least 4% when engine speed is greater than 575 RPM.
^ Map sensor greater than 4.6 volts.

ACTION TAKEN (VCM-A WILL DEFAULT TO)
The VCM-A will turn "ON" the Malfunction Indicator Lamp (MIL) when DTC P0108 is reported and 1 failure has occurred. The VCM-A will substitute a calculated value for the MAP sensor value so acceptable performance is maintained.

DTC P0108 WILL CLEAR WHEN
The VCM-A will turn the MIL "OFF" after three consecutive trips without a fault condition present. A history DTC will be cleared if no fault conditions have been detected for forty warm-up cycles [coolant temperature has risen 22°C (40°F) from start-up coolant temperature and engine coolant temperature exceeds 71°C (160°F) that same ignition cycle] or the Tech 1 clearing feature has been used.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

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

1. With the engine at idle, transmission in neutral and all accessories "OFF," MAP voltage should be about 2 to 2.5V. If MAP voltage is greater than 4V, then an open or a short to voltage may be present in the MAP signal circuit.
2. If disconnecting the MAP sensor does not produce a reading of less than one volt, than the problem may lie somewhere in the signal circuit.
3. If the test light does not light, the MAP sensor ground circuit may be open.

DIAGNOSTIC AIDS
An intermittent ground in CKT 432 or CKT 474 will result 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. This information is used by the VCM-A 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 ±0.4 volt. Also, Manifold Absolute Pressure (MAP) Output Check can be used to test the MAP sensor. MAP Sensor Output Diagnosis

Refer to Intermittents. - Intermittent Malfunctions

Disconnect sensor from bracket and 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.

NOTE: Make sure electrical connector remains securely fastened.