DTC 33

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 maximum EGR signal.

Test Description:
Numbers below refer to circled numbers on diagnostic chart.
1. Confirms Code 33 and that fault is present.
2. If the ECM recognizes and sets Code 33, low MAP signal, the ECM and wiring are OK.
3. Checks to determine if solenoids are stuck closed.
4. Checks to determine if there is a short to ground in either solenoid circuit, or if there is a fault in the ECM.