1991 Ford Mustang EGR Valve Position Sensor Replacement Cost

The EGR valve position sensor monitors the operation of the exhaust gas recirculation valve for the powertrain control module (PCM). This allows the PCM to constantly map the position of the EGR valve, and make fine adjustments to optimize vehicle and emission control system performance.

The PCM will send reference voltage to the EGR valve position sensor, and, in return, it expects the EGR valve position sensor to relay back an altered voltage. The altered voltage, or signal voltage, will be translated by the PCM as the exact position of the EGR valve in its regular path of travel. In other words, it will tell the PCM to what extent the EGR valve is opened or closed. This allows for the PCM to self-check the EGR system for proper operation, and to acknowledge when and to what degree the EGR valve should be opened or closed.

If the EGR valve position sensor fails, at the very least the check engine light will be illuminated. This will indicate that there are fault codes pertaining to an emission system component failure stored in the PCM. If the position sensor reads correctly, but within its normal range, the engine may run roughly, stall at idle, misfire, or hesitate to accelerate under normal conditions.Fuel mileage will likely suffer as well.

Anytime the check engine light comes on, especially if flashing, the vehicle should be seen by a professional, or, at the very least, scanned to identify the on-board diagnostic trouble codes stored in the engine control module. The check engine light should not be ignored, especially if the issue pertains to the EGR system. Not only will a faulty EGR system lead to poor gas mileage and the mentioned symptoms, but it can ultimately lead to failure of the vehicle to start and run. Having the vehicle serviced sooner, rather than later, is in the best interest of the owner and vehicle.

EGR systems are known for issues, but some makes and models are more prone to failures within the system. Since this system operates in a hot environment and is constantly exposed to exhaust gases and carbon deposits, it is reasonable to expect a repair for this system at some point. For the EGR valve position sensor, it is not as common a failure as it would seem. Though it is an electronic component exposed to high heat, these sensors are constructed for these conditions, and have no moving parts. However, predicting the service life of the EGR valve position sensor is not possible.

Technicians understand that when an on-board diagnostics code (OBD-II) is stored in the PCM and references the EGR valve position sensor, there are four possibilities. The PCM may be faulty if the sensor is reporting correctly, there could be faulty wiring in the circuit for the EGR valve position sensor, the EGR valve may be stuck or sticking, or the position sensor may have failed. First, the technician will check the reference voltage and signal voltage at the EGR valve position sensor. Next, the signal voltage will be confirmed by a diagnostic scan tool. According to that voltage, the position of the EGR valve is noted and compared to a chart which outlines which position corresponds to what amount of voltage. If the EGR valve is not in the proper position according to the signal voltage, the sensor will be diagnosed as faulty. If the signal voltage sent is different than the PCM has recorded, however, the PCM may have failed, and any inconsistency in the circuit will result in probing of the wires for that circuit. Lastly, if the EGR valve is in an improper position, but the EGR valve position sensor is reading that position correctly, the check engine light will likely still point to the EGR valve position sensor though the EGR valve or solenoid has failed.

Replacing the EGR valve position sensor is as easy as locating the sensor, removing the electrical connectors, and either unscrewing the sensor or mounting hardware. It would be uncommon to find that the EGR position sensor is difficult to remove once accessed. This is because most have the same basic design. Replacement is the opposite of removal, but significant deconstruction is necessary to access the EGR valve and position sensor on many vehicles.

We recommend thoroughly inspecting the sensor for signs of carbon buildup and exhaust gas leaks. This would indicate the EGR valve is leaking exhaust gases into the sensor. If this is occurring, the new sensor may suffer the same failure as the old sensor.

The EGR system is nearly as hot as the exhaust system, especially if the engine has been running under heavy load or high engine speed. Wait at least thirty minutes to one hour before servicing the system, or just ensure the EGR system components cool to the touch before proceeding. Also, not all vehicles use an EGR valve position sensor, so suspecting this component without testing and understanding the system may result in a failed attempt at repair.

Replacing the EGR valve position sensor is simple, but diagnosis may be slightly tricky.. As long as the EGR system and computerized automotive circuits are understood, this can be done by most DIY mechanics with a multimeter and a little time to spare. It is important that the DIY mechanic ensure that the specifications for the signal voltage from the sensor for the vehicle being serviced are correct. Some vehicles of the same make and model may have different specifications depending on engine size and year.