P031

Circuit Description

The Manifold Absolute Pressure (MAP) sensor is a sensor that changes resistance based upon manifold vacuum. The PCM provides a 5 volt reference and ground. The MAP sensor signal varies between ground and 5 volts as manifold vacuum varies. As MAP decreases, voltage decreases (low engine load, high vacuum). As MAP increases, voltage increases (high engine load, low vacuum). The PCM uses the MAP sensor values as an indicator of engine load. Code P031 sets when the PCM detects a MAP sensor signal that is too high.

Test Condition(s)

1. Codes P021 and P022 not set.
2. Engine running with throttle angle 20.5 degrees or less.

Failure Condition(s)

MAP value 103 kpa or greater for more than .25 second.

Action Taken

1. PCM turns 'ON' the 'SERVICE ENGINE SOON' MIL
2. PCM disables long term fuel trim.
3. PCM uses a substitute MAP value based on engine RPM and throttle position switch status.
4. PCM disables Evaporative Emission (EVAP) control solenoid.
5. PCM disables torque management.
6. Transaxle shift adapts are maintained at current levels.

Notes on Fault Tree

1. If Code P038 is also set, CKT 469 is open or shorted to voltage because MAP sensor and IAT sensor share the same return.
2. If MAP sensor or circuitry are shorted, PD02 will read 103-105 kPa.
3. If PCM data PDO2 goes to 10-16 kPa with the C127 unplugged, the fault is in the sensor or wiring from C127 (intake manifold side) to MAP sensor.
4. Checking CKT 432 for a short to battery. If wire OK, replace the PCM.

Notes on Intermittents

Code P031 could be set during an engine backfire, which would cause a rapid increase in MAP value. Check P031 snapshot for additional information.