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Working on a 97 f150 with a p0401 code. So far the dpfe sensor, egr valve and a broken egr tube have been replaced. The rubber hoses on the egr tube are clear . The throttle body ports have been cleaned also. When I check the voltage on the dpfe signal wire I get 1.04 but only goes up to 1.18 when vaccum is applied to the egr valve. I cant think of anything else to check. What am i missing?
This is the crossover year for the soup can style to plastic if you have the coup can than its likely your problem if not well have to do some vacuum testing with a vacuum gauge
So the engine does actually run badly with vacuum applied to the EGR valve, but the DPFE voltage never goes high? :huh:
Were you observing the DPFE voltage at the sensor directly, or on scan data? Just wondering about wiring integrity from the sensor to the PCM, as an excessive resistance problem could account for that.
Could you do some voltage checks at the DPFE sensor? I'd like to know what voltages you see on all three wires, plugged in and unplugged. That'll let us know quickly if there's a wiring problem or not, and what the next step is.
I agree with Tyler here, definitely sounds like an issue with the DPFE sensor. Something to note is that the signal wire for this sensor is a pull down design, unplugging the sensor should make scan data show 5v.
"Without data, you are just another person with an opinion."
I haven't checked the vaccum reservoir yet it's been to cold. I did measure the the 3 wires with a voltmeter. Signal wire was 1.1 connected 5.4 disconnected. Ground wire was 0 both ways and the the other wire was 5.3 both ways. Something else that I noticed was when I put vaccum on the small side of dpfe port the voltage goes up on the signal wire.
I believe this is a pull down design circuit. So if you have 5v ref, 0 ground and 5v on signal with it unplugged it does seem that the wiring is good. It is possible that you got a bad new sensor
kman200 wrote: I haven't checked the vaccum reservoir yet it's been to cold. I did measure the the 3 wires with a voltmeter. Signal wire was 1.1 connected 5.4 disconnected. Ground wire was 0 both ways and the the other wire was 5.3 both ways. Something else that I noticed was when I put vaccum on the small side of dpfe port the voltage goes up on the signal wire.
Sweet, thanks! Like Nandor69 said, that indicates good wiring.
Seeing higher voltage with vacuum on the small port... How far does the voltage go up? And how much vacuum are you applying? Not trying to grill you! Just thinking that you're onto something.
If this has the soup can style resivor they get pin holes and you end up with low vacuum to the egr valve if you have a vacuum gauge you can measure vacuum at the solenoid and compare it to intake vacuum that will tell you if that is your problem
Thanks for all the help so far guys. I found the vaccum reservoir it was the plastic type. I don't have a vacuum gauge but could probably get one. I used the vacuum solenoid by grounding one of the wires and another vaccum line from the truck to check the egr valve with. When I put vaccum to the dpfe port with the same line the voltage went over 5 volts .
Today I decided to try my old egr tube since it had been broken long before I had this problem . I stuck it on and checked the voltage at the dpfe sensor and the volts went up over 4. I thought I must have bought a bad tube so I went and got another one . I put it on but still the volts never went up. The only difference between my old one and the new ones is the orifice shape. I ended up welding the bottom half of the new one to my old one. Seems to be working good.
kman200 wrote: Today I decided to try my old egr tube since it had been broken long before I had this problem . I stuck it on and checked the voltage at the dpfe sensor and the volts went up over 4. I thought I must have bought a bad tube so I went and got another one . I put it on but still the volts never went up. The only difference between my old one and the new ones is the orifice shape. I ended up welding the bottom half of the new one to my old one. Seems to be working good.
What tha... :huh: I don't suppose you could get pictures of this for me? Just interested to see the difference.
When you mentioned being able to put vacuum to the DPFE and getting a signal change, that's when I started thinking about something wrong with the tube and hoses. You'd said the hoses were clear, and I (mistakenly) figured your new EGR pipe had to be good! :lol: I know better than to assume 'new' means 'working correctly'.
Just thinking out loud here... If the orifice was larger on the new tube, then the difference between the two DPFE ports wouldn't be as large, and thus the DPFE sensor wouldn't show the correct signal during EGR operation. Am I thinking about this correctly?
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Both of the new ones are made by Dorman for my truck. I don't know about the orfice size but that does make sense. That was the first thing I changed when I got the p0401 . I think the original problem was clogged ports on the throttle body which was the second thing I fixed.
I KNEW IT. :lol: :lol: Dorman is so hit and miss, it's super frustrating.
I don't know about the orfice size but that does make sense. That was the first thing I changed when I got the p0401 . I think the original problem was clogged ports on the throttle body which was the second thing I fixed.
Agreed. Really sucks when the parts let you down.
I'm gonna slap a [FIXED] on this one. Thanks for keeping us updated!
Topic Author
Just thinking that you're onto something. 