Code P031, Shorted Map Sensor Circuit: Notes

MAP sensor output signal voltage is a DC voltage varying with manifold pressure. PCM provides a 5-volt reference signal and ground. MAP signal varies between zero and 5 volts as manifold pressure changes. As MAP decreases, voltage decreases (low engine load, high vacuum). As MAP increases, voltage increases (high engine load, low vacuum).

PCM uses MAP sensor values to indicate engine load. A high MAP reading indicates heavy load and low MAP indicates low load. Code P031 is designed to set when PCM detects a MAP sensor signal out of high limits.