Nice when Murphy's Law not a factor!

[ozrocker]

Actually when I disconnected (electric And vacuum)the DPFE , I noticed NO difference
whatsoever in the idling or revving. Maybe it's just a Joisey thing eh CAP
And myself, I won't even call or go in a Pepboys.

                                                                                                     Oz

[CAP1]

Actually when I disconnected (electric And vacuum)the DPFE , I noticed NO difference
whatsoever in the idling or revving. Maybe it's just a Joisey thing eh CAP
And myself, I won't even call or go in a Pepboys.

                                                                                                     Oz

 nah. there is no vacuum there.

 what that sensors purpose is, is to tell the computer if egr gases are flowing properly, and how much. it does this, by those hoses. on the tube to the valve, there's an oriface. on each side of that oriface, there's one of those tubes connected. the oriface creates a pressure differential. hence the name "delta pressure feedback sensor". this differential is converted to a voltage. at idle, most of these should show about 1.5v, slowly rising as the valve opens. most i've dealt with top out around 4.7v.

 most often these sensors go bad, due to moisture from the exhaust system getting into them. you can actually remove the sensor, and tap the hose connectors on the counter, and see the water come out. i was tlking with another tech today.....he's so old, i feel young. he's never seen a dpfe sensor stop a car from running either.

[icepac]

I've seen about 60.

The difference is that every car I saw was there for an engine management issue.

No brake jobs, no timing belts.......just pure diagnosis for 12 hours a day for 3 years.

If you saw the 15 to 35 cars a day I was seeing at that period of my life, you would also have diagnosed and found just as many.........because the sensor was the problem.

Nowadays, I finish cars in which others have gotten in over thier head.

[CAP1]

I've seen about 60.

The difference is that every car I saw was there for an engine management issue.

No brake jobs, no timing belts.......just pure diagnosis for 12 hours a day for 3 years.

If you saw the 15 to 35 cars a day I was seeing at that period of my life, you would also have diagnosed and found just as many.........because the sensor was the problem.

Nowadays, I finish cars in which others have gotten in over thier head.

 you don't seem to understand. at pretty much every shop i've worked at, i have been the diagnostic guy. i got them all. they didn't come to me after someone couldn't figure them out(most of the time), but rather they came to me FIRST. hence, they got diagnosed properly the first time. the other stuff was given to others first, if i was diagnosing. if i was doing a "grunt" job, and a diagnosis came in, then i was pulled off of it to do the fun job.

 but i must not be as uber as you....most i've ever done in a day, is 11. that just came about a month and a half ago, so that was 11 with a couple running problems, normal grunt work, customer intake, make the estimate, sell the job, price and order the parts, do the job, then customer care when they came to get their cars.

[icepac]

OK......so how many defective DPFE sensors have you diagnosed in your lifetime?

Me?  At least 200 if not more.

Of those, 60 would not run or communicate with a scan tool.

Might have something to do with the water intrusion you mentioned and the corrosion that results from that.

[CAP1]

OK......so how many defective DPFE sensors have you diagnosed in your lifetime?

Me?  At least 200 if not more.

Of those, 60 would not run or communicate with a scan tool.

Might have something to do with the water intrusion you mentioned and the corrosion that results from that.

 over a hundred. each and every one of them had water in them. customers were/are always amazed that water comes out of them.

[ozrocker]

Me? I'm no trained mechanic. A backyard one, starting with my Grandpa
when I was 6.
I've diagnosed 1. Like I said, I was getting a bad code for the sensor.
You seem , even starting at 1st reply, to have an animosity about me
getting away with a 3 buck repair on an overpriced, unneeded sensor.
I'm happy for you that you've diagnosed over 200.
Good Luck with your endeavor for 200 more.

                                                                                                                                 Oz

[CAP1]

Me? I'm no trained mechanic. A backyard one, starting with my Grandpa
when I was 6.
I've diagnosed 1. Like I said, I was getting a bad code for the sensor.
You seem , even starting at 1st reply, to have an animosity about me
getting away with a 3 buck repair on an overpriced, unneeded sensor.
I'm happy for you that you've diagnosed over 200.
Good Luck with your endeavor for 200 more.

                                                                                                                                 Oz

 personally, i think it's pretty cool that you got it that easy. 

[icepac]

Hopefully no more diagnostic specialist duties.

I'm burned out from Blue Streak where needed 3 people to do my former duties (might have something to do with having worked 12+ hours a day for 6 or 7 days a week).

My duties as a toyota/lexus master technician weren't so much fun either when you realize that guys who can diagnose are outearned by parts replacers with zero skill because diagnosis does not pay at the dealership level.

If I ever consider dealership work again as a technician, I will claim that listening to heavy metal music has made it impossible for me to ferret out squeeks and rattles (NVH) and that I know nothing about electrical diagnosis but excel at brakes, services, and alignments.

I'm considering letting a Z car shop in california recruit me as that shop has the kind of action I enjoy most though my current job (unusual part time job) is interesting and will see me tomorrow at Kennedy Space Center's shuttle landing facility runway to assist in attemptiing a world record standing mile run of over 270mph.

These guys interest me but moving from south florida to california is a pretty big undertaking.

http://www.zcargarage.com/

[CAP1]

 pin 90(bn/wh)=v-ref
 pin 65(bn/lg)=signal return.
 sensor shares a common ground with the tps and a few other sensors.



unless i'm missing something, if this sensor shorts to ground, it will at most conduct full reference voltage to pin 65, thus convincing the ecu that there is full egr flow. it will not create damage on pin 90, as it's already supplying 5v constantly.

 so basically 5v will go straight through the dpfe sensor, and land on pin 65 which will then read 5v, and the ecu will trip a code for high voltage.

 tell me what i'm missing. prove me wrong.

[icepac]

You are referencing shorting to Vref to signal return.

I was referencing Vref shorted to ground............You know........that third wire you failed to mention.

You also forget that the regulator that provides this reference voltage also powers the ecu itself..........so.....shorti ng it ground will render the ecu non-powered.

[CAP1]

You are referencing shorting to Vref to signal return.

I was referencing Vref shorted to ground............You know........that third wire you failed to mention.

You also forget that the regulator that provides this reference voltage also powers the ecu itself..........so.....shorti ng it ground will render the ecu non-powered.

 again, unless i'm missing something.......vref is already grounded, otherwise no voltage would flow through the resistor to the signal return line.

 save me some time and show me in a schematic how what you say is possible is so.

[icepac]

again, unless i'm missing something.......vref is already grounded, otherwise no voltage would flow through the resistor to the signal return line.

 save me some time and show me in a schematic how what you say is possible is so.

LOL......Vref is not "grounded".

Yes, you were missing something.

If Vref were grounded, the two sensors in your diagram would never see 5v.

[Tigger29]

For the record I've diagnosed probably 500 bad DPFE sensors (Due to P0401/P0402 codes) in my career and when I worked at Ford for 14 months I fixed about 100 of them which had brand new aftermarket DPFE sensors installed by replacing the brand new aftermarket DPFE with a Motorcraft DPFE sensor.  Then the customer would usually get mad at me because Autozone would claim that their DPFE sensor failed due to water in the exhaust and refuse to give them a refund! <facepalm>

Icepac you claim that 50% of cars with DPFE failures will not run and this is flat out false.  I did run into a few old ford pickups that had an actual EGR sensor mounted on the EGR valve that had shorted out and killed the reference circuit as well but this was not a DPFE sensor.  Of the hundreds of DPFE sensors I've replaced I never ran into one which prevented the vehicle from running.

I'm not saying that it isn't possible but based on what you've described you only see the "worst of the worst" but what you see in no way reflects 50% of the DPFE failures.. no even close.

[CAP1]

actually, it is not possible. 5v will not short a ecu. the vref is in fact grounded. the voltage travels through a resistor to ground. the signal return reads the varying voltage, which is changed through the pressure,  through the resistor.

 once again, i could be missing something, but i've been through the diagrams(can't find any internal circuit diagrams for the units anymore), talked with techs with loads more experience than myself, and they all say the same thing.

 tigger.....if i'm not mistaken, the only way that shorting the dpfe would prevent a car from running, would be if it took signal away from the tps, cts, and possibly the iats?