2002 Cavalier - ECU not available from GM

[Greg Bloomfield]

I've owned a 2002 Bi-fuel (gas/CNG) Chevy Cavalier for over three years. I love it.

GM since Nov/08 [4-mpnths] cannot / has not provided to the dealer an ECM (electronic control module) needed to repair the Bi-fuel CNG function.

The dealer altered the car by removing fuses so the car runs on gas only until GM can provide the part. No date has been provided for the part to be provided.

Can you help? Isn't GM required under law to provide parts for at least 10 years?

Greg

[freedml]

Re: 2002 Cavalier - ECU not available from GM

I think it's industry standard to provide parts for at least 7 years after a model is discontinued, but I don't think there's a law requiring that.

Have you tried to have your ECU repaired or exchanged by a third party?

[siai47]

Re: 2002 Cavalier - ECU not available from GM

There is no "law" about maintaining repair parts for a certain number of years. The manufacturers try to maintain an inventory for a specific time period, however if there is a run on a part number, and the inventory runs out, usually you are out of luck. There are many parts for the 2003-2004 Cavaliers that are already out of stock let alone parts for the earlier systems. The cost of a new ECU for a 1998-2002 Cavalier usually exceeds the price that most people would pay to get the CNG system running again. In addition, the new ECU's need to be flashed for the specific vehicle. Be sure that the ECU is the problem because there are a lot of other things that like to fail before the ECU. ECU's from cars that came from States that used road salt usually suffer from some corrosion that may get into the unit itself either through the case or connectors. Also a wiring problem (short) can lead to a failure. The fact that removing fuses lets the car run on gasoline but it will not run on CNG with the fuse installed leads me to believe that the ECU is still functioning (at least partially). What codes did the dealer retrieve when he scanned the car? Does the red light on the fuel gauge selector come on for a bulb check when turning on the key? Is the fuel gauge reading CNG levels? Did the dealer go through the flow chart on possible problems other then the ECU before he pulled the fuse? Unless the ECU fell of the car, you may want to continue verifing that it is the problem. From time to time, the ECU's are available on E-bay at reasonable prices. That would be the first place I would look. Also, have your dealer check parts at other dealers--you might find one there. As a last resort, you can PM me as I have a brand new ECU sitting on the shelf .

[siai47]

Re: 2002 Cavalier - ECU not available from GM

BTW-I bought some parts a while back from a guy in California on E-bay. He has a junkyard and was scrapping out a couple of Cavaliers. I know he had all of the CNG components on E-bay at one time. He may still have what you need if you contact him. His E-bay user id is "wightriver". Search E-bay memebers for him and then contact him about your ECU needs. Worth a try.

[freedml]

Re: 2002 Cavalier - ECU not available from GM

Doesn't the cav have a 2nd ECU for the NG system? Running on gasoline doesn't tell you that the Alt Fuel ECU is ok.

[siai47]

Re: 2002 Cavalier - ECU not available from GM

You are correct, there is a totally different ECU for CNG operation. However, if the AF ECU failed completely, the car would just start and run on gasoline (you wouldn't need to pull any fuses). The fact that it won't run on gasoline with the "CNG" fuse in place means that the AF ECU is trying to operate. The dealer must have pulled some codes--its possible the AF ECU failed, however, it is one of the most expensive parts of the system, hard to find, hard to replace and must be programmed--and if it turns out not to be the problem you aren't going to be very happy . The point is, verify that everthing else (including the GMS/MCV) is working before condeming the AF ECU. Does the car ever start with the CNG fuse in place? There is a time limit that it will try to start on CNG before switching to a gasoline start of about 10 seconds. Have you tried to just hold the key in the start position for 10 seconds and see if it starts on gasoline? The codes, the operation of the little light on the fuel switch and what happens when you hold the key over to start for 10 seconds all help to deterimine if the AF ECU is the cause of your misery.

[Insight]

Re: 2002 Cavalier - ECU not available from GM

My thanks to Siai47 for many posts on CNG chevy vehicles.

I purchased an AFECU off Ebay last week for $76+shipping. It was from a 99 salvage. I plugged up in 02 that would not recognize AFECU when above ~50 F. Car is running great and much smoother than previous.

This was not done without following the trouble shooting guide completely and then verifying the fact it was the AFECU. I kept daily records of every drive and condition experienced after purchase to help identify problem. I removed the old computer from vehicle and put it in freezer briefly before reinstalling on car when it wasn't working. Worked when cold, not when warm. This AFECU has been opened to inspect and clean up. There does not appear to be any possible way to identify defective chip or to repair as the board is varnished after manufacture. This bad unit is up for grabs if anyone is into electronics and reverse engineering. Send me a post if you would like to pay for shipping of bad unit.

Now enjoying $1.11 CNG in Tulsa.

[RonBarlow]

Re: 2002 Cavalier - ECU not available from GM

I am new to the forum but think I may have the same problem. Are you talking about the computer unit that sits under the battery on a Cavalier? Mine is shot and I need to find a new one. I hadn't thought about ebay.

[siai47]

Re: 2002 Cavalier - ECU not available from GM

Well sort of under the battery--It's more like under the drivers side headlight behind the bumper. What is your car not doing? The AFECU's do fail but usually it is something else that makes them run poorly or keeps them from running on CNG.

[RonBarlow]

Re: 2002 Cavalier - ECU not available from GM

Thanks for your response. Let me give you a little more information. I couldn't get the car to start on CNG. It starts immediately on gasoline. There is no hesitation when starting like it's trying to start on CNG before switching to gasoline. Checked all electrical connections to the tank and valves. Have power at the control valve. Couldn't establish a ground from the ECM to the valve. Checked ECM and found it totally corroded. Tried to clean the ECM and the unit fell apart. There are electrical burn marks on some connections. Also what appears to be a chip fell out. Can these units be rebuilt? If so, do you know anyone who works on them? From what I'm reading I'm looking at some major dollars even If I can find a ECM. The car runs great and I'd like to keep it if I can get it running on CNG.

[siai47]

Re: 2002 Cavalier - ECU not available from GM

I think when chips start falling off a PC board, its time to give up on it. I would start looking around on E-bay for one to come up. 1999 through 2002 ECU's will work---you can reprogram them if you like to fit your exact vehicle, however, most should work straight out of the box. I had a couple of good used ECU's but sold the last one to a memeber on this site some time back. Around $200 would be a fair price for a used ECU. If you buy off E-bay make sure the seller guarantees it won't be DOA. Plug it in to your car and if everything is OK, take it apart and seal the housing with "Yamabond" sealant to keep the corrosion out. Anyone who owns one of these cars and is in a location that ever uses road salt (or is in a coastal enviornment) needs to do this.