P031

DTC PO31:

Sensor Circuit:

DESCRIPTION
The Manifold Absolute Pressure (MAP) sensor is a sensor that changes resistance based upon manifold vacuum. The Powertrain Control Module (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 CONDITIONS
Tested continuously.

FAILURE CONDITIONS
MAP value 107 kPa or greater for more than 0.25 second.

ACTION TAKEN
1. PCM turns "ON" the "Service Engine Soon" Malfunction Indicator Lamp (MIL).
2. PCM sets BARO equal to 92 kPa.
3. PCM uses a substitute MAP value based on engine RPM and throttle position switch status.
4. PCM disables long term fuel trim.

NOTES ON FAULT TREE
1. If PCM data PD02 goes to 14 - 16 kPa with the sensor unplugged, the fault is at the sensor or sensor connector.

2. Checking for an open circuit from pin "A" of the connector to PCM pin "2A5" (ground). If the ground is open, the signal voltage will always be high.

NOTES ON INTERMITTENTS
Manipulate MAP sensor connector, MAP wiring, and PCM connector while observing PCM data PD02. Apply and release vacuum to the MAP sensor vacuum port using a vacuum source. If the PCM data PD02 immediately jumps to greater than 108 kPa, repair intermittent MAP sensor fault. If wiring and connectors check out OK, substitute a known good MAP sensor and retest.