My check engine light is still coming on in my 97 F-150 with a 4.6L engine.I have done the following but to no availe. Could I possibly have a bad DPFE sensor that I replaced not more than 3 months ago? And if so are there more robust ones out there then the ones from Autozone.


1. Took off throttle body and EGR valve and thorougly cleaned EGR passage
and reassembled and ran engine.

2. Tested EGR valve operation by shorting wire on egr regulator which
caused the EGR valve to open and stalling the engine.

3. Check reference voltage on DPFE at 5 volts

4. Check signal voltage on DPFE with engine warm and only got 1 volt.

5. Disconnected Harness form DPFE and checked signal voltage and got 5
volts.

6. Disconnected hoses at DPFE with engine off and hooked my hand vacuum
pump to test for blockage and found no blockage.

 

First off, we need to know the code you're getting. Sounds like a P0401.

All your checks save one are good, valid tests which, unfortuately, don't pinpoint the problem... They do tell us a few, certain components are working.

That one is to check the DPFE output voltage at idle. Since there is no EGR commanded at idle, the voltage you measured is probably correct for that condition.

Sounds like you have a few good tools, so:

Monitor the output of the DPFE sensor while applying a vacuum to the EGR valve. As vacuum increases, EGR flow should increase and the output of the DPFE should also rise, all in proportion.

If you have a vacuum guage, you can measure the delta vacuum across the EGR orifice while the EGR flow is varied. It is this change in vacuum that the DPFE sensor is supposed to measure.

Do you have a scan tool that will allow you to directly check PIDS? If so, you can watch what the computer is reading in realtime. You can also, by jumpering the DPFE harness (disconnected) output signal line alternately to ground and Vref , see if the interconnecting signal line to the PCM is good.

We can tell from your experiments that the EVR solenoid, EGR valve, and EGR ports are functional.

Welcome aboard. Let us know what happens.

Steve

 

I don't know if you can use this information but my Mercury Grand Marquis 95 with 4.6V8 has 2.51 V at DPFE sensor HOT IDLE.
But the problem is i don't know if this is correct.
When i drive; the voltage will go down en i can see how much % flow it has.
Strange thing is: VREF is not 5V but 2.51V.