Map Sensor Check

Manifold Absolute Pressure (MAP) sensor measures amount of vacuum in EGR circuit and sends signal back to ECM. ECM compares MAP sensor's signal with duty cycle of EGR. If ECM recognizes a difference between MAP sensor signal and EGR command, it will set check engine light. When a vacuum error is sensed, ECM will turn check engine light on after 10 seconds and will not go off until key is turned off.

1. Check for ECM reference voltage at terminal "C" of MAP harness. Voltage should be approximately 5 volts.
2. Check for open or ground between MAP circuit and ECM. When properly grounded, voltage should be approximately 5 volts.
3. Check for proper circuit from MAP signal wire to ECM terminal "B". High voltage readings of approximately 5 volts indicate an open ECM terminal or ECM. Low voltage reading indicates an open, grounded wire, or faulty MAP sensor.

Fig 1: MAP Sensor Check