P0401 P0402 DPFE Questions

[v8mountaineer5.0]

So I have a 1998 V8 5.0 Mountaineer - AWD. It's completely stock except for the MAC Cold Air Intake. So a few weeks ago when i checked it was just throwing just a p0401 (insufficient flow). Now its throwing p0401 and p0402(excess flow). So I decided to do some tests on the EGR system.

So here is what I have found so far:
The EGR valve holds vacuum and does not leak. The vehicle stutters and starts to stall when I apply vacuum to the EGR valve.(This means the passages are clean enough right?)

I back-probed the DPFE signal wire to ground and measured ~ 5 volts at idle. I hooked the Vacuum gun up to the EGR valve and applied vacuum the car began to stall but there was no change in the DPFE signal.

I back-probed the vpwr to make sure there was a constant power supply to the dpfe which was about 5.10 volts (near the same voltage as the DPFE signal). SO THE POWER IS GOOD.

With the Vacuum pump still connected to EGR: I also back-probed the return signal wire at the DPFE (middle wire on connector) to ground. The signal range varied from about 200mV to 100 mv. The norm for this signal was about 180 mV decreasing to about 160 mV. There was no change in this signal when vacuum was applied to the EGR.
The resistance across the signal return to ground was 50 ohms.

So I'm thinking I have a fried DPFE because the Signal Voltage is way too high at idle. I've read it should be like .55v or 1.0 v for the metal DPFE.

I'm kinda guessing the power shorted to the return signal.!! Causing the PCM to be confused.

I also have a p0340 code from my camshaft sensor which has been going on for a while could this be related / receiving a stray signal from the DPFE short?

Once it stops snowing I'll do some tests on the EVR to see if it is functioning properly.Anyone think it could be the EVR instead?

Thanks in advance for any help

 

[1998Exp]

If this is the original DPFE on your '98, consider yourself extremely lucky. The model that they used at the time usually didn't last more than 2-3 years before hot exhaust penetrated the electronics and messed things up. If your probing is correct (seems that it is...) and there is no response to vacuum, it's not the EVR. By the way, if you have a decent scanner, it's easier to read the DPFE output that way rather than by poking wires.

 

[v8mountaineer5.0]

Cool. I'm pretty sure its the original DPFE since its the metal one. I had to backprobe the wires since the USB ODB2 scanner I have can only read codes (++ $90 for the ford PID package.) Looks like its time to go to Ford for a new sensor.

Thanks for the help.

If this is the original DPFE on your '98, consider yourself extremely lucky. The model that they used at the time usually didn't last more than 2-3 years before hot exhaust penetrated the electronics and messed things up. If your probing is correct (seems that it is...) and there is no response to vacuum, it's not the EVR. By the way, if you have a decent scanner, it's easier to read the DPFE output that way rather than by poking wires.

 

[v8mountaineer5.0]

So now I'm confused. There are three pins on the DPFE connector.I found a diagram of the connector saying that: the top pin is the DPFE signal, the middle is the signal return and the bottom is the Power(V-ref). SO is the top wire the signal coming IN from the PCM or the signal going OUT to the PCM?

On the top wire I get 5v to ground.
The middle wire I am assuming is just a ground? because when I test it to another ground i get nothing.!!When I test a source to it I get the source voltage.
The bottom wire has a voltage of 5v also.

My dilema is the following.. (why are there two 5v wires?)

If the top wire is the signal out..It never changes from 5v even when I hit the EGR with vacuum enough to stall it out.
If the middle wire is the DPFE signal OUT (which i dont think), when I tested it against ground it had negligible resistance(150Mv) and no significant change at all.

Sorry for the long hard to understand rant

This guy has the exact same qeustion /problem.

http://www.justanswer.com/ford/4ce4v-ford-ranger-2wd-working-97-ranger-2-3l-dpfe-sensor.html

 

[1998Exp]

I don't have a picture of the connector, so can't refer to your up/down/middle designation, but if you can see the wires, here is the color code:
BR/W: 5V Ref
BR/LG: DPFE Out
GY/R: Signal Ret (GND)

Signal Ret is not directly shorted to ground at the sensor, but I think that it should show continuity to GND through the PCM (I may be wrong on that...) In any case, check continuity of this wire to Pin 91 at the PCM connector and also take a good look at both sides of the connector to see that the contacts are not bent/broken/pushed in (#91 is closest to the center on the left side of the bottom row).
By the way, you don't have to pay your Ford dealer the big bucks for a new DPFE. They are widely available everywhere, both as Motorcraft part with the Ford numbers, and as very inexpensive aftermarket substitutes. It's probably worth spending the $30-$40 on one of those and simply try, instead of spending all this time chasing your wires and connector pins - just a suggestion...

So now I'm confused. There are three pins on the DPFE connector.I found a diagram of the connector saying that: the top pin is the DPFE signal, the middle is the signal return and the bottom is the Power(V-ref). SO is the top wire the signal coming IN from the PCM or the signal going OUT to the PCM?


On the top wire I get 5v to ground.
The middle wire I am assuming is just a ground? because when I test it to another ground i get nothing.!!When I test a source to it I get the source voltage.
The bottom wire has a voltage of 5v also.

My dilema is the following.. (why are there two 5v wires?)

If the top wire is the signal out..It never changes from 5v even when I hit the EGR with vacuum enough to stall it out.
If the middle wire is the DPFE signal OUT (which i dont think), when I tested it against ground it had negligible resistance(150Mv) and no significant change at all.

Sorry for the long hard to understand rant

This guy has the exact same qeustion /problem.

http://www.justanswer.com/ford/4ce4v-ford-ranger-2wd-working-97-ranger-2-3l-dpfe-sensor.html

 

[Turdle]

There is your problem. If the sensor is connected and you see 5v on the signal line, the sensor ( or possibly pcm) is shorted. Disconnect the sensor , then turn the key on and probe again for voltage on the connector please.
Post the signal line voltage disconnected.

This could be causing the cam sensor code, due to the fact the 5v line in is shorted to ground.

 

[v8mountaineer5.0]

The signal line voltage is 5v even with the sensor disconnected.

Does this mean I have my vref shorted to signal?

There is your problem. If the sensor is connected and you see 5v on the signal line, the sensor ( or possibly pcm) is shorted. Disconnect the sensor , then turn the key on and probe again for voltage on the connector please.
Post the signal line voltage disconnected.

This could be causing the cam sensor code, due to the fact the 5v line in is shorted to ground.

 

[v8mountaineer5.0]

So. I finally figured out why the signal wire is at a constant 5v.
Heres what I read:
"The PCM uses a voltage drop method to read the DPFE. The signal wire actually has 5 volts on it, exactly the same as the 5 volt reference wire does. In the at-rest position, the DPFE drops this voltage to 1.0 volt. Some older model DPFE sensors dropped the signal voltage to as low as .5 volts at rest. As the DPFE senses a pressure change across the orifice, its internal resistance climbs. "

But... Shouldn't it only be a constant 5v only when a bad DPFE is connected?

I'm guessing I have a short somewhere VREF-signal?

http://d-tips.com/general/articles/article.aspx?id=29

 

[v8mountaineer5.0]

DPFE replaced!!

I finally got to replacing the DPFE this morning. It's kind of a pain in the ass for the 5.0 v8. the bolt on the left side is pretty hard to get to without a real small 1/4" ratchet and some various length extensions. I also found it easier to remove the EVR solenoid first and then take off the DPFE and bracket. Good luck not losing the bolt on the left side. Other than that install's really pretty simple.
Also note that the plastic vacuum hoses ford originally used for the EGR and vacuum solenoid are extremely brittle after 13+ years. I broke it and had to replace.

Took it for a good drive and as of now my p0401, p0402, and cmp p0340 are gone. So hopefully the cmp code was due to my shorted DPFE.

edit: CMP p0340 code is back after a good long drive. Looks like that will be my next project.