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has anyone had this problem before? Got a fresh tank of gas last week at night. Next morning start my 1994 SLS and it acted like it was having a heart attack. Stalling,surging knocking and backfiring. read the board and went to the fuel regulator valve and replaced it. While I was at it and had the engine top open I put a new fuel rail in and redid all of the injector seals and a new map sensor. Started my baby up and it ran like a new car. I let it run up to temp because it had been sitting for a week. Waiting for parts, Drove it 1 mile and the car started acting up again doing the same thing. so I cleared all the codes and got it to idle for around 20 minutes with no stalling and here are the codes that showed up.PO23,53,83,95 and So44. My Manuals are all pointing to the ICM or Crank sensors. Has anyone else had these problems Thanks Steve T.

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Hmm....can be 4 or 5 issues related to the codes...

First...always check the battery cables on Cadillacs. Internal corrosion causes about 20% of stuff like this.

Crank sensors. They are most likely ok. About $50 each.

ICM. Could be a ignition control module failure. About $300. So I would try to verify this first before replaceing.

PCM. Could be a PCM failure. Its has that sound to it....gets a little warm and then goes into failure mode. A reman Delco PCM is about $140. There is a TSB about some weak '94 PCMs floating around. You would think that it would show up before 9 years....but possible.

On the '94s theres also the issue of wire harness rub thru where the harness rests on the edge of the transmission end pan. All it takes is a single stand or nick....you often cant see them. And they will set codes or shut the engine down. TSB on this also.

So....check the battery cables..

Check the harness resting on the trans...

Tap test the PCM. See if you can induce the failure mode. If not...

Try replacing the PCM.

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Thanks logan I hoped you would be the one to answer this for me. I will start my trouble shooting today before the next storm hits us tonight. Car has 184,000 miles but I"m going to keep her she always comes thru for me and still looks good. if it is the wiring running along the trans can that section of wiring be replaced?

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Good Morning Steve - My car, a 1994 Concours, has not done exactly the same thing, but has come back with the P023, P025 & P083 PCM Codes. It always starts, sometimes rather rough and other times very smooth and normal. I have had it at an independent shop to solve these code problems and nothing yet. I am very interested in your results, maybe it will help solve my codes also. I have already replaced the ICM. My thought is that the crankshaft sensor is the next stop.

Thanks, Jim

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  • 12 years later...

Although I'm responding to an old post, it was a post that got my 1994 Concours up and running again.  I bought a near mint condition 1994 (41,000 miles) 2.5 years ago and have put 5,000 miles on it myself.  About a year ago, it began having a rough idle.  It ran fine when I was driving it.  I took it to the dealer and they suggested a new starter.  I did it. (Did not need that though.)  I then took it to my old trusty mechanic who suggested a tune up.  I did it.  It ran a little better but the idle was still rough.  (Now, $2,000 into it and it was still rough.) I let it sit in my garage for the last year until I really had time to do research.  Logan's recommendation to replace the PCM ("ECU" on this vehicle) was the answer.  I bought a re-manufactured ECU for like $150 and replaced it myself.  Thanks to all the wonderful videos and great advise on line, my '94 Cadillac runs great once again.   

The ECU is under the glove box.  Remove kick plate and the ECU is the silverish box on the right side with red/white/blue plugs in the bottom. 

  3. Remove the brownish nut and slide the ECU to the right and it should come down.
  4. Unlatch cables. 
  5. Insert the PROM from your existing car into your new ECU. 
  6. Put everything back.
  7. Turn ignition to run (not on) and let the Security light turn off.
  8. Now, turn the car on.

You need to run it for a few minutes and then drive it for some miles before the ECU has updated itself.  My "Check Engine Light" was on for like 15-20 miles before it turned back off.  You may have to reset the ECU. 

Do your research folks, it pays off!



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Is that blue? More like a cloud blue. I am so jealous. What a beautiful car. Very nice rims also. Makes me miss my 1996. What a great body they had


Nice, clean, luxury= fine automobile

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Yes this body style is beautiful.  Thanks for the info @Steve 94 Concours 

We have seen the 4.9 ECM cause the type of problem you experienced.  I can recall at least 3 owners over the years fixing roughness and misfires replacing the PCM/ECM

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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