This is on a '99 F-250, 5.4. I'm trying to fix a "check engine soon" light problem. I am getting a 401 code - EGR flow insufficient. Replaced egr valve control solenoid and egr valve appears to work okay under vacuum. In checking DPFE sensor, I pulled the connector off and ran voltage checks on each of three female ends. The top and bottom each reading 4.5 to 5 volts, the middle nothing. I ran a small wire into female end and reconnected to DPFE sensor with the key "on" and read 0 volts for each of the three connectors. Thinking I may have screwed up somewhere, I slowly checked the connector and removed it and checked voltages again with the connector disconnected and measured voltages again. It appears I lose the voltage once the connector is plugged into the sensor. Does this make electrical sense? Is there a way to test the sensor off of the truck? Any help is appreciated.

 

first of all
what did u use to get the 401 code ?
did u use a star tester ?

 

I got the code using the actron III OBD II tester which I purchased awhile back. I posted another related question on 3-14-01 for some background information.

 

I would clean the EGR passages and retest.
The PCM supplies voltage to 2 connectors and the sensor changes this voltage according to the flow of Exhaust gas past the sensor.

Regards

Jean Marc Chartier

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00 F-150 XLT SC Flairside 4x4 4.6 w/5spd 3.55LSD
Warn XD9000i, skid plates, Draw tite class III,
Rancho RSX Reflex shocks, MAC 8.8 Axle Girdle
BFG 285/75 R16 MTs,
Borla Cat Back, Headman Headers,
Custom air intake system with modified
air box, Ported Throttle body,
Shortened MAF sensor tower,
K&N air filter,
Superchips

 

I had the EGR valve off the other day and there was a very slight layer of carbon on the inside of the inlet tube and coming off the throttle body, but certainly nothing to indicate any blockages. I'm really suspecting the sensor. Is there any way to check it out

 

Okay - here's where I am at. Hooked up a set of jumper wires from connector to DPFE sensor. I am getting power to the unit (approx 5 volts) that comes in the top and bottom wires. However, on the middle wire (sig rtn) I am showing 0 voltage even when I apply 10 Hg of vacuum. This looks to me as if information is not being sent back to the PCM from the DPFE which leaves me SOL! Now, again, I'm diagnosing this problem based on information from a Chilton's manual which I have found to be inaccurate once already on information concerning the EGR solenoid. Any thoughts? Shouldn't there be some voltage on the signal return wire?

 

Russty
the signal return is a ground wire. one of the other wires is +5v & the other is signal+. hooked up, you should not have +5v on the signal wire, only on the red or v+ in wire. the signal out should vary from 1 to 4 or so volts. if you are seeing 5v on 2 wires, the sensor is probably bad.

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97 Lariet-sc-4.6-4x off road-auto-3.55 LS-
superchip-Airraid-Perma-cool electric fan & controller

 

redlariat - I'll take another look at it tomorrow. It's frustrating, however, as I'm to the point that I don't feel I can count on much of anything in the Chilton's manual as being accurate. The manual specifically instructs to make voltage readings on the SIG RTN circuit. They do show three wires between the sensor and the PCM: VREF, SIG RTN, and DPFE SIG. I'll take readings on all, but I would guess the DPFE SIG would be the wire returning info to the PCM from the sensor.

 

Russty
the dpfe is the voltage from the sensor that should change under different conditions. the vref is the +5v into the sensor. you could use the sig return for the -meter lead. if the dpfe signal wire stays at +5v, you have a bad or stuck sensor.

 

It is most likely the dpfe sensor..they go out all the time... the best way to check it is with a scan tool and monitor pid data.. you need to see a voltage fluctuation at the egr or dpfe pid when changingthe load on the engine... it has a 5 volt reference so it will be between .5 and 4.5 volts. if it doesnt change when the egr valve opens and the egr valve flows..then it is the sensor...
if u pull a vacuum on the valve the engine should stumble or stall... if u hook a vac guage into vac line tothe valve it should show a vacuum under load, expecially in the higher gears...good luck

 

Here is where I'm at. Already replaced EGR solenoid. Checked voltage on DPFE sensor which showed a voltage of 5 volts coming in and a signal voltage starting out at around .5 volts and rising to near 4 volts after running the engine for about 10 minutes. My manual indicates voltage should be "approximately 4 - 6 volts" at operating temp so I am assuming my 3.9 volts is close enough (?). To rule out the EGR valve itself, I borrowed a vacuum pump from Autozone and attached it to nipple on top of EGR and brought it up to 7 Hg and I left it there for about 15 minutes and it held the vacuum. I then attached the vacuum gauge to the vacuum line leading to the EGR valve and ran the truck for about 15 minutes and placed into different gears and never registered any vacuum at all. Should there have been some vacuum action at some point before that? I am also checking out the MAF sensor; however, my manual shows a round connector and my '99 5.4 has a flat connector. If someone has a Ford manual - could you tell me the description of the four wires - red (voltage), black (gnd), tan (?) and blue (?). Which is the signal wire? Thanks again to all who have responded. I'm determined to solve this problem.