NOTE: Prizm LSi uses ECM terminal B1 for reference voltage.

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.

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

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

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

Use the Manual With the Right Hardware

When to See a Mechanic

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