Fix a Ford DPFE EGR sensor problem
The Ford DPFE and EGR systems are unique and you must understand how they work if you want to diagnose and fix them.
This article explains how DPFE works with the EGR system on Ford vehicles.
Car makers recycle exhaust gas back into the engine to reduce combustion temperatures and pollutants. However, in order to make the engine run smoothly car makers have to meter the recirculated exhaust, injecting it into the intake manifold only under the proper conditions. To do that, they have developed exhaust gas re-circulation (EGR) valves and sensors to detect how well the EGR valve is working. The sensing portion of the system is important because the exhaust contains soot, and that soot can clog up the metering portion of the EGR valve.
The Ford EGR system uses 3 components:
• an EGR valve that opens and closes a passage from the exhaust to the intake manifold,
• an Electronic Vacuum Regulator (EVR) that opens and closes passages from the intake manifold to the diaphragm of the EGR valve, and
• a Delta Pressure Feedback EGR (DPFE) that measures the change in exhaust pressure before and after a restriction in the exhaust tube that leads up to the EGR valve.
Here’s how Ford EGR works
When certain driving conditions are met and the computer wants exhaust gas recirculation, it provides a pulsing voltage to the electronic vacuum regulator (EVR). The EVR is a solenoid valve. When it opens, it allows intake manifold vacuum from port 5 to flow into port 6 on the top side of the EGR valve. The vacuum pulls up on the diaphragm, lifting the pintle off the pintle seat. With the pintle off its seat, exhaust pressure forces exhaust gas up through the EGR tube, the EGR valve, and into the intake manifold at port 4. On the way up to the EGR valve, the exhaust gas passes through a restriction. The DPFE sensor hoses are connected to ports 1 and 2—before and after the restriction. By comparing and reporting the differences in pressure, the computer can determine exactly how much exhaust gas is flowing through the EGR valve.
What goes wrong with the Ford EGR system
Exhaust gas contains water vapor. Ford did consider the ramifications of this water vapor getting into the DPFE and forming ice. So they programmed the computer to ignore an EGR malfunction if the temperature is below 32°F. Unfortunately, Ford didn’t give enough consideration to the impact of corrosion inside the DPFE, and that’s what causes most of the EGR related problems.
Do it yourselfers and professional technicans make an all-too-common mistake if they automatically replace the EGR valve when they see an EGR related code. In fact, the valve itself is usually the most reliable component in the system.
How to troubleshoot Ford EGR
Step 1) Check the condition of the vacuum hoses going to the DPFE sensor and the EVR. Look for cracks or tears. Replace the hose if you find any.
Step 2) Check the operation of the DPFE with the engine off, key in the run position. Using a digital voltmeter, check for voltage on the brown/light green wire. Look for a reading between .45 and 1.1 volts. If your reading is outside that range, you have one more voltage check to perform before replacing the sensor. Check the voltage on the brown/white wire. It should read 5 volts. If it doesn’t, the sensor isn’t getting power from the computer. Then it’s a whole new ballgame. If you have 5 volts, and the reading from the brown/light green wire is outside the range, replace the DPFE. After replacement, perform the voltage check again to eliminate the possibility that the EGR valve is not seating properly.
Step 3) Leave your meter connected and start the engine. The voltage SHOULD NOT CHANGE! That’s because there should be no EGR flow at idle. If the DPFE voltage changes, either the EGR pintle isn’t seating properly and it’s allowing exhaust flow past the seat, or the DPFE is bad.
Step 4) Remove the EGR valve and check the condition of the pintle, pintle seat, and the EGR passages. They will be coated with black soot. But the passages should not be clogged and the pintle should move off its seat with the application of vacuum. Clean
the pintle, pintle seat, and passages with carb or throttle body cleaner.
© 2012 Rick Muscoplat
Posted on by Rick Muscoplat
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