Map Sensor Check

An Absolute Pressure Sensor (MAP) is used to monitor vacuum in EGR vacuum circuit. It senses amount of vacuum in circuit and sends a signal back to ECM. This signal is compared to EGR duty cycle signal. If there is a difference in the ECM command and the MAP sensing, a CEL is set.

1. This step checks for a 5 volt reference at MAP sensor harness. Normal reading at terminal "C" of MAP harness should be about 5 volts.
2. This step checks for an open ground in MAP circuit to ECM. Normal reading is about 5 volts with a good ground.
3. This step checks for proper circuit from MAP signal wire to ECM terminal "B." Readings near 5 volts indicate an open ECM terminal or ECM. Low voltage indicates an open or grounded wire, or faulty MAP sensor.

Fig 1: MAP Sensor Check