Code 31, Map Sensor, Open Or Shorted Circuit: Notes

WARNING: This page is about a different car, the 1992 Geo Prizm. However, it is still accessible from the selected car via links, so may be relevant.

The MAP sensor responds to changes in manifold pressure. ECM receives a signal voltage that varies between 1-1.5 volts at closed throttle idle, to approximately 4-4.5 volts at wide open throttle (low vacuum). If MAP sensor fails, ECM substitutes a fixed MAP value and uses TPS to control fuel delivery.

NOTE: Test numbers refer to test numbers on diagnostic chart.

Verifies 5-volt reference is available from ECM.
Verifies ECM is grounding the circuit.