View Full Version : DPFE Sensor Diagnostics HOWTO

08-15-2016, 06:27 PM
I recently fixed trouble codes 332 and 335 on my SC the other day. These two codes on the '94 - '95 SC's point to a possibly failed Pressure Feedback Sensor or some type of issue with the EGR system. If you're like me ditching the EGR setup is not an option and diagnosing the problem is needed. Don't assume your EGR valve is bad. This is a common mistake and from what I've heard\read the EGR valves rarely fail.

(The DPFE sensor monitors and measures the pressure with the EGR valve. This prevents the valve from malfunctioning and allowing too much exhaust into the intake manifold at one time.)

There are three wires plugged into the DPFE Sensor on the '94 - '95 SC. The Brown and Light Green wire is the flow signal that the PCM listens to for engine management. The Brown and White wire is the Ground (Earth).The Gray and Red wire is your supplied 5v.

Now let's verify the DPFE sensor is monitoring the pressure drop across the orifice correctly.

1) Plug a vac pump onto EGR valve. Or just grab a clean vac hose and use your mouth for suction.
2) Attach the red lead of your multi-meter into the back of the DPFE wire connector, Brown and Light Green wire.
3) Ground the black lead of your multi-meter to the block.
4) Select Volts DC on your multi-meter.
5) Crank up the vehicle and let idle. Return to the engine bay.
6) Take a gander at the voltage being displayed on multi-meter. Should be somewhere around .8 - .9 volts.
7) Apply vacuum to the EGR valve and notice the rough idle of the engine. This is normal, no need to worry.
8) The voltage should change on the multi-meter to a higher number, 1.1 V to 4.5 V.

If the DPFE sensor is working correctly you should see the voltage increase when you open the EGR valve.

If you did not witness an increase in voltage during vacuum and a decrease when you let off the vacuum your sensor is not working correctly and should be replaced.

If no voltage was witnessed during the test verify the Gray and Red wire is supplying the 5v needed for sensor operation.

332 C,R EGR Valve opening not detected
335 O EGR sensor voltage out of range


08-15-2016, 11:27 PM
Some good advice. I don't have an EGR on my SC, but I do on my Mustang, and it threw a CEL a couple of months back, and the code was that it was related to the EGR. Following some advice that I'd read online to blow some air into the EGR valve and see if the engine stalled, I had ruled out the valve and narrowed it down to the DPFE sensor, which had saved me from buying the EGR valve.