Learn more about the functioning of the DPFE sensor
DPFE means “Delta Pressure Feedback of EGR”, Delta means “difference” or “change”, so the DPFE Sensor reads changes in the pressure of the EGR system.
What is a DPFE Sensor?
The DPFE Sensor tests the amount of emissions being sent back into the system and communicates with the Powertrain Control Module. In order to lower the amount of nitrogen oxide coming out the exhaust, the federal government mandated the addition of Exhaust Gas Recirculation (EGR) Systems as part of the 1990 modification of the Clean Air Act.
Nitrogen oxide is produced under high temperatures and pressure. By recirculating inert (they won't burn) emissions back into the combustion chamber, ignition temperatures are lowered and less nitrogen oxide is produced by the combustion process. EGRs reduce emissions by 25% and nitrogen oxide emissions by 60%. If your vehicle is a 1990 model or newer, it has a EGR.
However, the DPFE sensors that come standard with a vehicle have a tendency to fail quickly.
DPFE Sensor Failure
When the DPFE Sensor starts failing, it gives the PCM bad information. The DPFE Sensor is less sensitive, and the PCM thinks less recirculate gas is being burned than is actually so. Trying to compensate, the PCM opens up the actuator too much. This excessive amount of EGR combined with the air coming in via the throttle body leans out the fuel mixture, causing a lean misfire, which is the "stumble" or "hesitation" that is common as the DPFE Sensor fails. The DPFE sensor in the Focus is not very robust, requiring frequent (every 30k miles or sometimes less) replacement or a work around. Note that complete DPFE sensor failure is a very slow process, and the check engine light won't come on until the DPFE sensor is pretty much done for.
If you're experiencing stumble or hesitation while cruising, and think that it might be related to DPFE sensor failure. If the stumble goes away, then your DPFE sensor is more than likely failing. Of course, replacement of the bad DPFE sensor is the official recommended fix for this problem. However, a while longer to perform but makes for a nice semi-permanent solution that won't cause any damage or check engine light warnings if the DPFE Sensor hasn't completely died. It takes a few seconds but is good for making a quick diagnosis to see if the EGR system is leaning out and causing problems.
Do you have a problem with your DPFE sensor?
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Preventive engine cleaning enables you to restore engine parts rather than replacing them, thereby saving vehicle owners on costly parts, such as a new turbocharger (1.350€ - 3.100€), catalytic converter (600€ - 2.000€), DPF (600€ - 2.000€) or EGR valve (370€ - 500€).
These problems result mainly from poor combustion, which stifles the engine.
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1. Open the hood of the vehicle. Locate the DPFE sensor, which is near the EGR valve, behind the upper intake manifold, between the firewall and engine. The sensor is a small square with two vacuum hoses on the bottom and a wire harness coming out from the side. The location will vary slightly from make and model. Check your repair manual for exact location and a detailed diagram.
2. Disconnect the two vacuum hoses from the sensor by giving them a firm tug.
3. Turn the ignition key to the "On" position. Do not turn the engine off. You want the sensors to run and PCM to turn on, but the engine to remain off.
4. Connect the negative (black) multimeter lead to a ground point, such as the negative battery terminal. Clip the positive (red) lead to the DPFE sensor signal wire. The sensor has three wires; the signal wire is the first wire on the left of the unit.
5. Allow the multimeter to register the voltage. Ford DPFE sensors should read between .45 and .55 volts. All other makes should read between 0.8 and 1.0 volts. If the sensor is not within the appropriate range, the sensor is faulty and should be replaced.
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