On Board Diagnostics Question
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RWD 19xx-1984 DeVille and Fleetwood,
1985-1996 Fleetwood and Brougham Forum Discussion, On Board Diagnostics Question in Past Cadillac Vehicle Discussion; I recently picked up a '96 Fleetwood and right after getting a passing eCheck (emissions testing for those of you ...
  1. #1
    CadillacSam91 is offline Cadillac Owners Member
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    On Board Diagnostics Question

    I recently picked up a '96 Fleetwood and right after getting a passing eCheck (emissions testing for those of you outside of northeast Ohio) my check engine light came on. I ran to Autozone on my way home and I found its a P0400 egr valve fault. (Lucked out on that, CEL = fail = no plates). It's been coming and going so I figured its a simple case of needing to clean it. No biggie. I tried to run the test on the climate control while it was on and got nothing. Only two dashes (--) when I ran the 0-00 test. What am I missing?

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  3. #2
    HUF's Avatar
    HUF
    HUF is offline Cadillac Owners Connoisseur
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    Re: On Board Diagnostics Question

    EGR code can be intermittent. EGR valves are a known problem on LT1 engines. It can cause hesitation. Replacing it is extremely easy. I would recommend to get EGR valve for F body (1993-1997 Camaro), which performs better on these engines (stronger spring).

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    CadillacSam91 is offline Cadillac Owners Member
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    Thanks. I saw that somewhere before. I was just going to clean it, would a used one be acceptable or are they too hit-or-miss?

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    HUF's Avatar
    HUF
    HUF is offline Cadillac Owners Connoisseur
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    Re: On Board Diagnostics Question

    Quote Originally Posted by CadillacSam91 View Post
    Thanks. I saw that somewhere before. I was just going to clean it, would a used one be acceptable or are they too hit-or-miss?
    No. A used EGR valve can look just fine (plunger moves freely, the diaphragm is intact, etc.) but the spring may be weak. It is not an expensive part and installation is very easy, so do just that - get a 1993-1997 Camaro EGR valve on Amazon and you will eliminate another source of possible drivability issues in the future.

    Your EGR valve is most likely the original one. It is time to replace anyway. I was chasing hesitation source for years. Replaced lots of parts and even the original EGR valve with a used one... A NEW valve solved the problem in five minutes.

  6. #5
    turbojimmy's Avatar
    turbojimmy is offline Cadillac Owners Connoisseur
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    Re: On Board Diagnostics Question

    Powertrain codes can only be read with an OBDII scanner on the '96. You won't get them through the HVAC module. The '96 is unique and misunderstood in that regard.

  7. #6
    CadillacSam91 is offline Cadillac Owners Member
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    Quote Originally Posted by HUF
    No. A used EGR valve can look just fine (plunger moves freely, the diaphragm is intact, etc.) but the spring may be weak. It is not an expensive part and installation is very easy, so do just that - get a 1993-1997 Camaro EGR valve on Amazon and you will eliminate another source of possible drivability issues in the future.

    Your EGR valve is most likely the original one. It is time to replace anyway. I was chasing hesitation source for years. Replaced lots of parts and even the original EGR valve with a used one... A NEW valve solved the problem in five minutes.
    Thanks. I'll do that when I'm back at school.

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    Quote Originally Posted by turbojimmy
    Powertrain codes can only be read with an OBDII scanner on the '96. You won't get them through the HVAC module. The '96 is unique and misunderstood in that regard.
    Okay. That's slightly disappointing. I'm assuming the other diagnostic systems (-01 to -04) still function normally? Also, there is a lot of info on what the diagnostic trouble codes are, but what about -05 to -38? I found rpm and the two coolant temperatures, but there are a lot more parameters than that.

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