04 Deville EGR problems
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, 04 Deville EGR problems in Past Cadillac Vehicle Discussion; Hi all - So, we've been seeing EGR related codes on a 04 Deville - both a P1404 and a ...
  1. #1
    jkstark is offline Cadillac Owners Member
    Automobile(s): 04 Deville
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    04 Deville EGR problems

    Hi all -

    So, we've been seeing EGR related codes on a 04 Deville - both a P1404 and a P0404. Replaced the EGR valve thinking that would solve the issue, but nothing...

    I went through a series of checks on the system based on instructions on another site, which was basically checking voltages on the harness. I was able to confirm that the +5V reference signal is available on pin D of the connector. I was under the impression that pin E (red wire) was supposed to have a 12V on it. This is the wire that is defined as the "EGR Solenoid High Control" and connects to the ECM to pin 2 on connector 2.

    I compared to a 01 Buick that has a different engine, but a very similar EGR valve. On that particular vehicle, pin E *is* a 12V supply, but I realize that this is not necessarily the same on the other...

    I do notice a rise in the voltage on that pin when the key is turned on, and the engine is run, but the highest that I was able to get that pin to go to is about 2.5V. If that pin is indeed designed to run the solenoid as I suspect, then the 2.5V is not going to be anywhere near high enough to activate the EGR and the codes would make complete sense.

    Anybody have any thoughts and/or recommendations as to where to look next, or what to test?

    Thanks!

    Kris

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  3. #2
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
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    Re: 04 Deville EGR problems

    Might help if you tell us what P1404 & P0404 mean.

  4. #3
    jkstark is offline Cadillac Owners Member
    Automobile(s): 04 Deville
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    Re: 04 Deville EGR problems

    Sorry -

    P0404: Exhaust Gas Recirculation Circ Range/Perf

    P1404: Exhaust Gas Recirc (EGR) Closed Pos Perf

  5. #4
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
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    Re: 04 Deville EGR problems

    You probably could have gotten away with cleaning the old one, but I am surprised that replacing it did not solve the problem.

    How long has it been? Did you clear the codes and they returned?

  6. #5
    jkstark is offline Cadillac Owners Member
    Automobile(s): 04 Deville
    Join Date
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    Re: 04 Deville EGR problems

    Well...

    I did try to clean the old one, which seemed to have had a bit of stick on the closed position - nothing major, but just enough that it might have caused the issue. Reinstalled that one, and cleared codes. Within about 60 miles, the code was back... Pulled the valve out again, cleaned more thoroughly, including as much as I could of the manifold housing and reinstalled. Again, one of the codes was back relatively soon. Figured that it would be worth trying a new valve just to make sure, but that did not allow the codes to stay off either.

    That's what prompted me to see if the voltages made sense, based on a slightly older Buick with a similar EGR, and instructions also found at easyautodiagnostics. Looking at the schematics for both cars, it appears that the reference high signal comes from the ECM, and was mentioned as a 12V potential on the diagnostics site. On the 01 Buick, 12V is what I get, but on the 04 Caddy, under 1V with engine off key on, and up to about 2.5V with engine on. I *think* that this line is what powers the EGR solenoid itself, with the ground provided from the ECM as well.

    Thinking about it now, I suppose I should really test the voltage across the two solenoid control points, and not one against a ground, but in any case, I wasn't sure if the solenoid high reference should have been +12V at all times or not...

    I'm at a loss otherwise...

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