Code P1400 DPFE Low Voltage (No CEL)
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From: San Diego, CA
Code P1400 DPFE Low Voltage (No CEL)
Finally got a code! P1400 - DPFE Low Voltage. Got Haynes Manual out and it says back probed it should read between .20 to .70 volts while cold and 4.0 to 6.0 volts hot (warmed up). Mine reads .97 volts @ cold or hot.
After reading a few posts around here it's been said to have an affect on a lot of things such misfire symptoms and vibrations. Could this be what's been going on with my truck? What would be the symptoms?
Any input would be greatly appreciated, Sean
After reading a few posts around here it's been said to have an affect on a lot of things such misfire symptoms and vibrations. Could this be what's been going on with my truck? What would be the symptoms?
Any input would be greatly appreciated, Sean
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From: St. Louis (Out in the woods)
The Haynes manual is incorrect. Doesn't matter if the engine is hot or cold, the EGR is NEVER requestd while at idle. It only functions at cruise speeds.
If you wish to manually test the system, backprobe the connector while applying a vacuum to the EGR valve. As the vacuum is increased/decreased, you should see a proportional change int he DPFE output voltage. If the EGR valve is operational and the throttle body ports are free-flowing, you should be able to kill the engine (or nearly so) just by applying vacuum to the EGR valve.
From the PCED:
Steve
If you wish to manually test the system, backprobe the connector while applying a vacuum to the EGR valve. As the vacuum is increased/decreased, you should see a proportional change int he DPFE output voltage. If the EGR valve is operational and the throttle body ports are free-flowing, you should be able to kill the engine (or nearly so) just by applying vacuum to the EGR valve.
From the PCED:
Diagnostic Trouble Code (DTC) P1400 indicates that Self-Test has detected a DPFE SIG circuit input below the minimum.
Possible causes:
-- Leaking upstream pressure hose.
-- DPFE SIG shorted to GND or SIG RTN.
-- VREF shorted to GND or SIG RTN.
-- Damaged D.P.F. EGR sensor.
-- Damaged PCM.
l Key on, engine off.
l Access DPFEGR PID with a Scan Tool.
l Is DPFEGR PID voltage less than 0.2 volt?
Yes
The D.P.F. EGR sensor voltage is less than the acceptable minimum. GO to «HE2».
No
INSPECT pressure signal hoses for leaks. SERVICE as necessary. If OK, fault that produced DTC P1400 is intermittent. GO to «HE6».
Possible causes:
-- Leaking upstream pressure hose.
-- DPFE SIG shorted to GND or SIG RTN.
-- VREF shorted to GND or SIG RTN.
-- Damaged D.P.F. EGR sensor.
-- Damaged PCM.
l Key on, engine off.
l Access DPFEGR PID with a Scan Tool.
l Is DPFEGR PID voltage less than 0.2 volt?
Yes
The D.P.F. EGR sensor voltage is less than the acceptable minimum. GO to «HE2».
No
INSPECT pressure signal hoses for leaks. SERVICE as necessary. If OK, fault that produced DTC P1400 is intermittent. GO to «HE6».
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From: San Diego, CA
Thanks Steve. I'll check it out per your recommendations. Haynes says to test the EGR valve exactly as you say, but doesn't say to apply vacuum to the EGR while backprobing the DPFE for voltage.
I've had a tough time tracking down exactly where my problem lies and if I had the money, I would've already taken it to Ford for the WDS test. Oh well, eventually I'll find it and I'm learning a lot in the process.
PS - Thanks for answering the other Forum as well!
Sean
I've had a tough time tracking down exactly where my problem lies and if I had the money, I would've already taken it to Ford for the WDS test. Oh well, eventually I'll find it and I'm learning a lot in the process.
PS - Thanks for answering the other Forum as well!
Sean
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From: San Diego, CA
Hey Steve,
Applied 6 lbs of vacuum to the EGR while backprobing the DPFE and it went from .97 volts to 3.+ volts and almost killed the engine so again, I'm barking up the wrong tree. Thought I was onto something.
Thanks for your input though
Sean
Applied 6 lbs of vacuum to the EGR while backprobing the DPFE and it went from .97 volts to 3.+ volts and almost killed the engine so again, I'm barking up the wrong tree. Thought I was onto something.
Thanks for your input though
Sean
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From: San Diego, CA
projectSHO89,
I replaced the DPFE yesterday. Reset the computer and the strangest happened. The truck used to downshift out of overdrive kind of hard before I changed the sensor (example: crusing at freeway speed 65 - 70 and when I let off the accelerator it felt like I tapped the breaks) and now it shifts really smooth. It's been like this since before and after the tranny rebuild.
Could a bad DPFE sensor have caused this problem? Maybe it had something to do with the way the vacuum works with an automatic transmission?
I replaced the DPFE yesterday. Reset the computer and the strangest happened. The truck used to downshift out of overdrive kind of hard before I changed the sensor (example: crusing at freeway speed 65 - 70 and when I let off the accelerator it felt like I tapped the breaks) and now it shifts really smooth. It's been like this since before and after the tranny rebuild.
Could a bad DPFE sensor have caused this problem? Maybe it had something to do with the way the vacuum works with an automatic transmission?
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Joined: Oct 2002
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From: St. Louis (Out in the woods)
Originally posted by 5.4 F150
projectSHO89,
I replaced the DPFE yesterday. Reset the computer and the strangest happened. The truck used to downshift out of overdrive kind of hard before I changed the sensor (example: crusing at freeway speed 65 - 70 and when I let off the accelerator it felt like I tapped the breaks) and now it shifts really smooth. It's been like this since before and after the tranny rebuild.
Could a bad DPFE sensor have caused this problem? Maybe it had something to do with the way the vacuum works with an automatic transmission?
projectSHO89,
I replaced the DPFE yesterday. Reset the computer and the strangest happened. The truck used to downshift out of overdrive kind of hard before I changed the sensor (example: crusing at freeway speed 65 - 70 and when I let off the accelerator it felt like I tapped the breaks) and now it shifts really smooth. It's been like this since before and after the tranny rebuild.
Could a bad DPFE sensor have caused this problem? Maybe it had something to do with the way the vacuum works with an automatic transmission?
I'd just be happy it works better....
Steve