We have an updated look. Click here for information on how to manage your settings. If you run into any issues, please email [email protected]

Engine Control Module/Service Engine Soon Light

rmn2000rmn2000 Posts: 2
edited March 2014 in Cadillac
My 1988 Cadillac Eldorado with 76,950 miles on the odometer has endured the past two months with her "service engine soon" light coming on regularly, air conditioning failues twice (low refrigerant noted, a/c compressor off are the error codes) and now after getting the vehicle back from the repair facility the odometer reads "error." The manager of the facility has indicated that he problem is a faulty engine control module. Unfortunately this delayed revelation comes after $1300. in repairs on the engine, emission system, and air conditioner which were probably not necessary.

I initially took the car to the Cadillac dealership when the "service engine soon" light came on.... they politely told me that they did not service vehicles over 10 years old. I then went to the largest independent service provider in the Atlanta area where they ran their $80 diagnostic program and advised me that the egr valve required replacement and a tune up was recommended. I agreed to the 400. in work and waited a week for the repairs to be completed. When I picked up the car, everything seemed fine for a few blocks until...... you guessed it.. the light came on. I took it back to the facility and they kept it for a few more days before telling me that the light was not significant and if it bothered me I should take it to the dealer.

Within a week my air conditioner went out. After the same facility determined that a new compressor and all the extras were in need of replacement ($834.) I foolishly let them work on the a/c. When I got the car back (one week later) the a/c was working just fine. BUT now a new message was appearing.... on the odometer "error." I believe this is an indicator that the odometer has been altered. This week the new a/c failed again with the same error codes.

The manager now tells me it is a faulty "engine control module" and I would have to take it to the dealer. Needless to say, we are having discussions as whether the work they performed was worth any compensation or indeed were they liable for damages. I have an appointment on Monday with the Cadillac Service Center, but I wanted to try and obtain as much information regarding this early computer chips function as possible.

Is it possible that the engine control module could affect the emission system readings, the a/c controls, and the odometer. A friend told me that if they attempted to install a new or salvaged chip without following proper procedures the odometer would have to be reset. It makes sense that a central chip failure could produce a variety of errors, but all of these????

The car is running fine, but no a/c in Hotlanta is not a pleasnt experience. Especially with the two large service engine lights flashing....

Any input would be much appreciated.


  • vidtechvidtech Posts: 212
    if the engine is running good i would put a piece of tape over the check engine light.old cars regardless of mileage will nickle and dime you to death.myself,i would not have put the initial $1300 into a fifteen year old car.
  • swschradswschrad Posts: 2,171
    I would write to the zone manager of Cadillac and let them know that they have a stinker in their dealer service system. any business can refuse any job in this country, as long as they don't do it on discrimination against the auto owner. but for them to say "we don't do any car ten years old," is something I think GM ought to know about. they can probably refer you to a dealership elsewhere in the peach city that would be glad to replace the module, and do something about the guys who don't want to uphold the traditions of the line.
  • Buy an after market ecm and replace it yourself. It,s under the dashboard behind the glove box.
  • I know I should not have spent the $$$ to have a fifteen year old car repaired, but it was my late mother-in-laws. That alone should explain some of the rationale.... and I know too much emotional involvement with a car can be expensive, but with only 76k on the odometer (before it was reading error) made me think I had many more happy motoring miles left to go in the old Eldorado.

    I've sent a letter to the GM regional offices, but am waiting for the results of the diagnostic Cadillac performs, in case other issues surface.

    ......and I have to be honest gmlover1 and admit I had not even given any thought to an after market ecm since I had been dealing with Pep Boys I thought they would have had access to such items and would have been more than willing to reach behind the glove box and put it in for the high labor they have charged me. I will start searching for an after market ecm and a new mechanic. Thanks for your input and help.
  • 0patience0patience Oregon CoastPosts: 1,712
    Aftermarket ECMs. NAPA sells them and I think Carquest.
    Those are the only 2 I would buy aftermarket ECMs from.
    Personally, I would purchase from Auto-ECU. That is their specialty.
  • q45manq45man Posts: 416
    By law and convention the factory only has to keep making parts for 7 years most do so for 10 years as a service to buyers.

    Most business would be foolish to keep a parts inventory that old, hoping a 15 year old car would come in for service when the average car on the road is no older than 8.

    Luckily things were fairly simple in 1988 before OBD1 came in, in 1990. EGR dirt is really common on low mileage old cars drive slowly around town.
    I think you had multiple problems plus the ecu [?].

    $1300 is nothing on an old car barely 8 hours of work, we see 1990 models that need $5,000 due to letting things go for years and they are worth less than the repairs.

    Hope your tranny stays well!
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,482
    This is exactly why I think most 80s cars will not be saved in the future. No collector car value and too expensive to fix when the "old-tech" gets ornery.

    I think the shop might have had good intentions but probably did a lot of guessing as well. Precise and careful diagnostics are a fast decreasing talent and if you find someone who has this skill pay him whatever he asks because he will be cheaper in the long run.

    Well, don't mean to preach to you. Hopefully, the aftermarket ecm might solve some of these issues. I wish you good luck with it.
  • 0patience0patience Oregon CoastPosts: 1,712
    I totally agree with Mr Shiftright on the fact that "Precise and careful diagnostics are a fast decreasing talent and if you find someone who has this skill pay him whatever he asks because he will be cheaper in the long run."
    That is one reason alot of older mechanics are trying to help the younger mechanics to learn proper diagnosing of engine problems.
    Any mechanic, with the proper information (notice I didn't say tools) should be able to determine most driveability problems. I see it day after day where shops are trying to make it without a good information system.

    It used to be that the only thing you need information for was specs and torque values. Now, flowcharts and diagrams are part of the daily work on vehicles. Even the heavy trucks I deal with are now computerized and normal diagnostics just don't cut it anymore.

    Now, back to the ECMs. If you purchase and ECM from the dealer, you will pay. Aftermarket ECMs are reliable, provided the are purchased from a reliale source. Remember on most vehicles that there are 2 parts to an ECM. The ECM and the PROM and both are purchased seperately.
    THere are those who will tell you that you can use the old PROM in the new ECM, but to be honest, of every 5 ECMs I have replaced, at least 2 have had bad PROMs. If you are a gambler and you can afford the extra time, then go ahead and try the old PROM. Personally, I replace the PROM every time.
  • swschradswschrad Posts: 2,171
    the mid-body GMs with the bad steering racks are not going to be saved by anybody, except as a static museum exhibit. that's because they never redesigned the rack, just kept turning them around packing the same wear parts in the same worn racks with the same underdesigned flow. a lesson for our times.
  • I think your first problem is going to Pep Boys!
    I have several cars & Had two GMC Vandura Delivery Vans. I had Pep Boys working on them all.
    They have trouble just mounting a tire !!
    If the tire develops a shake...they can not figure anything out !!!
    I finally gave up on Pep Boys after so many problems...I now go to several independent service
    stations....some good, some not so good...but all of them are better than Pep Boys !!!
  • I'm not sure what the recommeded way to reset computer on my 2K Nissan to turn light off. I want to see if code pops up again. In my previous GM vehicle, I just pulled out the computer fuse marked "ECM". My fuse block has (2) 15 Amp circuits that are marked "Eng Cont". I want to aviod diconnecting battery to prevent losing saved Homelink and radio controls.Can anyone inform me how I can do this?
  • alcanalcan Posts: 2,550
    With a scan tool.
This discussion has been closed.