Code 31 Manifold Absolute Pressure (Map) Sensor - PRIZM: Notes

MAP sensor measures change in intake manifold pressure (vacuum). MAP sensor consists of a semi-conductor type pressure converting element, which converts a pressure change into an electrical charge, and an electronic circuit which amplifies and corrects electrical charge. ECM applies 5 volts to MAP sensor. Pressure change, resulting from engine load and RPM changes, is converted into a voltage input monitored by ECM. Low voltage input at ECM indicates low manifold pressure; high voltage input at ECM indicates high manifold pressure.

Code 31 will set if either of following conditions are met for at least .5 second:

• Voltage input at ECM indicates very low manifold pressure.
• Voltage input at ECM indicates very high manifold pressure.
  NOTE: Test numbers refer to numbers on diagnostic chart.

1. Checks for an open or short to ground in Yellow wire between ECM and MAP sensor.
2. Checks for an open in Light Green/Red wire between ECM and MAP sensor.
3. Checks for an open in Brown wire between ECM and MAP sensor and for a faulty ECM or MAP sensor.