Code 31, Manifold Absolute Pressure Sensor Open Or Shorted Circuit: Notes

The MAP sensor responds to changes in manifold pressure. The ECM receives a signal voltage that will vary from approximately 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 will substitute a fixed MAP value and use TPS to control fuel delivery.

1. This verifies that 5-volt reference is available from the ECM.
2. This step verifies ECM is grounding the circuit.