DTC 31

Circuit Description:
A Manifold Absolute Pressure (MAP) sensor is used to monitor the amount of vacuum in the EGR circuit. It senses the actual vacuum in the EGR vacuum line and sends a signal back to the ECM. The signal is compared to the EGR duty cycle calculated by the ECM. If there is a difference in the ECM command and what is at the EGR valve sensed by the MAP, the ECM makes minor adjustments to correct. When a major difference is sensed, the ECM recognizes a fault and sends a full EGR signal.

Test Description:
Numbers below refer to circled numbers on diagnostic chart.
1. Confirms Code 31 and that fault is present.
2. If the ECM recognizes and sets Code 33, high MAP signal, the ECM, MAP sensor and wiring are OK.
3. If the ECM recognizes and sets Code 33, high MAP signal, the ECM and wiring are OK.
4. Checks for 5 volt reference signal to MAP sensor. Normally, about 5 volts should be present, with the key "ON" at terminal "C."
5. Checks for an open in the FOR solenoid circuit.