Diagnostic Aids:

The MAP sensor output signal voltage is a DC voltage that varies with manifold absolute pressure. As MAP decreases, voltage decreases (low engine load, high vacuum). As MAP increases, voltage increases (high engine load, low vacuum).

The ECM uses MAP sensor values as an indicator of engine load. A high MAP reading indicates heavy load, and low MAP reading indicates low load. Code "EO31" is designed to set when ECM detects a MAP sensor signal out of high limits, MAP signal at 4.85 volts or more, and having a value greater than 105 KPA.

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).

If ECM parameter code "ED02" goes to 14-16 KPA with sensor unplugged, fault is at MAP sensor or sensor connector.
Check for an open circuit from pin A of sensor connector to ECM pin D12 (ground). If ground is open, sensor can not divide reference voltage to make signal voltage vary. The signal voltage is always high.