'90 Deville Diagnostics
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, '90 Deville Diagnostics in Past Cadillac Vehicle Discussion; Hi ya'll, I'm needing to know when I'm putting the '90 Deville 4.5L into diagnostics mode, which end of the ...
  1. #1
    Chzyrider is offline Cadillac Owners Member
    Automobile(s): 1990 Sedan Deville, '07 DTS
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    '90 Deville Diagnostics

    Hi ya'll, I'm needing to know when I'm putting the '90 Deville 4.5L into diagnostics mode, which end of the green connector do I ground? A or B?
    OR for some odd reason, do I ground it with the plug connected?
    green ground plug sm.jpg

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  3. #2
    brougham is offline Cadillac Owners Master
    Automobile(s): 1991 Cadillac Brougham D'Elegance 5.7 Litre
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    Re: '90 Deville Diagnostics

    Diagnostics mode? You mean to pull codes? It's just pressing and holding off and warmer on the climate control. What are you trying to do?

  4. #3
    13ir14314's Avatar
    13ir14314 is online now Cadillac Owners Fanatic
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    Sounds like he's trying to do it the old way for other obd1 cars. Short the plug and the MIL will flash the codes.

  5. #4
    Ranger's Avatar
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    Re: '90 Deville Diagnostics

    Could he be trying to time it? Didn't you have to disconnect a green plug to time those engines? Then again, he did say he was trying to enter the diagnostic mode.

  6. #5
    brougham is offline Cadillac Owners Master
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    Re: '90 Deville Diagnostics

    I think to time those years you just have to ground or do something with one of the pins in the OBD port under the dash. You used to just have to unplug a wire under the hood for older GMs maybe you can do it for these too, but you didn't usually have to do anything more then that.

  7. #6
    Chzyrider is offline Cadillac Owners Member
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    Re: '90 Deville Diagnostics

    I missed checking the "subscription" box for this thread to know when any replies came for the original post, so I finally checked back again and see there were some. ..oops.

    Yes, I am using the climate control panel and pressing OFF+WARMER to access the trouble codes and diagnostic test modes. I am not using a paper clip to short the A-B connections on the ALDL for mere code retrieval. I have a factory manual and for confirming the timing, it states to jump the A-B on the ALDL and ground the green connector.... BUT WHICH END? A or B (see photo)? That's the part of the process the book does not specify. This all originally started with the ISC making a rapid (5-7ct) clicking sound with KEY-ON as it's searching for a desired position before starting and would do similar after turning the key off. It's my father's car and he (wrongly, old-style thinking) adjusted the ISC out to raise the idle slightly because it was dying at stops.

    Now I'm trying to get it all reset accordingly, and test everything related to determine if we have a bad part for the original 'dying when approaching a stop' problem. I started with retracting the ISC via the control panel and reset the .060" clearance to the closed throttle lever. In checking the codes, I got: E12, E41, E98. I then suspect the worse in a bad cam sensor in the distributor for code 41, and predicted the code 98 according to the description was from being at too high of idle when shifting the trans into gear.

    In looking at the PCM data readouts on the climate control panel, the idle was about 850-900 and TPS at .9 degrees, so I looked and saw the throttle plates were dirty and sticky when closed, and this was holding them open slightly. After cleaning the throttle plates and clearing the codes, the readout for throttle position changed from .9 to .2 degrees. The idle dropped to about 600 in that little bit of movement, and no more clicking sounds from the ISC when turning key on-off. The codes did not come back at that time when rechecking.

    I wanted to follow thru with the timing check/adjustment, TPS test and any ISC re-adjustment, and finally the Idle Learn process, but I need to know which end of the green connector (next to the alternator) to ground to confirm the timing. Since it seemed to be running okay at that point, my father said the rest can wait for another day when I wasn't in a rush just to get it back on the road for him. Meanwhile I'm waiting for any replies to the original post, but realised today that I missed checking the subscription box to get notification of any replies. ...oops.

    Then just recently, an odd thing happened... the nut on the alternator shaft came off while driving and so did the pulley (so the squealing sound we heard at startup was apparently not the belt slipping). Luckily, he barely got around the block when this happened. We found the pulley on the side of the road but was missing the compression sleeve. I had a local rebuilder shop put a new one on, but in that time I had to disconnect the battery too for the R&R. After putting the alternator back on, I ran the idle learn process twice as described in the book, and I noticed the idle RPM's surged a couple times during this.

    Now the ISC is clicking again when turning key off (with engine already off). Then in test driving around the neighborhood up to the 40mph limits on those roads, I notice when letting off the gas pedal, it will maintain speed like the cruise control is on, but it's not..the switch was off.

    I cannot have my elderly father driving this car like that especially in traffic if it's holding speed when letting off the gas pedal and expecting it to slow down naturally. So again, I'm looking at going through everything related to this, including the timing check/adjustment. I'm going to recheck the throttle plates to see if they are sticking again and recheck for any codes later today.

    This engine has 147K miles on it with nothing major done to it other than regular oil changes, new spark plugs, and a couple new starters through the years. I would suspect the timing chain is likely stretched from the mileage and perhaps needing that slight adjustment to compensate. ...But again, I gotta be able to test it accordingly with the correct end of that green connector grounded. Which end do I ground???

    Also, the book does not specify any or which order for these test procedures. Since they are inter-related, which one do I do first, second, and so on?
    Any help here would be greatly appreciated. I got the right box marked now for seeing the replies. ;-) Thanks!

  8. #7
    Chzyrider is offline Cadillac Owners Member
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    Re: '90 Deville Diagnostics

    I got a chance to work on the car this coming weekend, but I'm still stuck on step #6 of 21 in testing components for rough idle.
    Sorry, I missed specifying before this was for proceedures under "Min Air, TPI and ISC Adjustments" Preliminary Checks, pg. 6E-C2-17 in my factory book.

    All these steps listed need that green connector grounded. Which side of the plug do I ground?
    *Is it as simple as just testing for the hot side and ground that one? Can anyone please help me here?
    I'm having a big brainfart here on this electronic stuff.


    #1 is PFI system check...
    #2 is running engine to warm it up to over 95 degrees C. and using P.0.4 climate control readout for exact temperature.
    #3 is exiting diagnostics mode.
    #4 is jumping A-B on the ALDL to check/adjust ignition timing to 10 degrees with a timing light.
    #5 is checking for vacuum leaks.
    #6 is "Disable the generator by grounding the green harness connector plug adjacent to the generator."

    That's all is says about the green plug and that's where I'm at in proceeding to the next main step: "Checking Min Idle Speed"

    #7 is "Entering diagnostics and select ECM override E.5.3 ISC Motor.
    #8 is "Press 'COOLER' on the ECC to retract the ISC motor.
    The rest of this procedure is for checking and adjusting the ISC off the throttle lever, and adjusting min idle screw if needed for spec idle speed.

    TPS check.
    #13 is checking voltage output of TPS with engine on at min air rpm setting.
    #14 is retracting ISC with engine off.
    #15 is adjust as needed to spec.

    ISC max extention
    #16 is extending ISC through the ECC.
    #17 is testing TPS output voltage, adjust ISC to spec.
    #18 is recheck, re-adjust as needed.

    TPS Learn
    #19 is turning ignition off, allowing 20 seconds for ISC to retract and perform TPS Learn.
    #20 is re-enter diagnostics and repeat step #19, for two full cycles performing TPS Learn.
    #21 is finally removing the grounding wire from the green connector.

    After that- Idle Learn Procedure
    #1 is .... and so on to step #6.

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