Part # for AF ECU

[alliedmotors Member Find all posts View Profile Close alliedmotors]

I believe I have a Cavalier with a bad ECU...full tank, operates on gasoline, indicator light is orange, no chk eng light. The part # on the ECU in the car is illegible.

Any luck rebuilding these things?

[siai47 Guru Find all posts View Profile Close siai47]

Re: Part # for AF ECU

You might want to troubleshoot further before condeming the ECU for a couple of reasons. First, the part retails for over $1700.00 . Second, if you want a new one, GM has none. There is a Chevy dealer in Utah that has one and the other one is located at Vintage parts in Wisconsin. Those are the last two in the world that can be purchased through the GM parts system. If you can find a used ECU that would be your best choice but I have not been able to come up with one. I have several 2000 thru 2002 Cavaliers and finally broke down and bought a new ECU through Vintage parts last week (they did have two) just to have a spare. You need to get a service manual to troubleshoot this system and you need someone with a Tech2 scantool. The ECU is located under the drivers side headlight along with a relay panel. I would check all of the relays (common easy to find) and the ECU connectors to be sure the relays work and the connectors are clean with no corrosion. Do to their location, the ECU and relays are prone to damage from water and salt spray. If that doesn't work, get the Tech2 hooked up and scan the system for problems. '98-'99 uses one style, '00-'03 a different part and the '04 shares one ECU for both gasoline and gasous operation.

[alliedmotors Member Find all posts View Profile Close alliedmotors]

Re: Part # for AF ECU

I can probably find one but I need a GM part number. Even if it isn't the problem, I'd like a spare as well.

[siai47 Guru Find all posts View Profile Close siai47]

Re: Part # for AF ECU

Part numbers, part numbers ----there are a bunch of them. The latest part number is a 52369822. This should be the P/N found on late 2002 and 2003 Cavaliers. Earlier superseded ECU part numbers in order (earlier design date first) are as follows: 52369663, 52369884, 52369386, 52370332, 52370421, 52370943, 52370944, 52370553, and 52369307. These ECU's are OBD compliant and fit Cavaliers from 1999 through 2003. The later P/N's are the better ones to use if you can find one. Good luck and good hunting!

[siai47 Guru Find all posts View Profile Close siai47]

Re: Part # for AF ECU

BTW--If you buy a new ECU it must be "flashed" (programmed) before it can be used. If you buy a used ECU, it will most likely work, however it may not have the exact program needed for your vehicle. A dealer can flash the ECU for you. Again, as I said before, I would troubleshoot the system carefully before investing in an ECU. Pay attention to the condition and operation of the four cube relays located above the ECU behind the headlight .

[alliedmotors Member Find all posts View Profile Close alliedmotors]

Re: Part # for AF ECU

Thanks, I have a salvage co looking for one and will match the #'s you gave me if anything comes up. I'm going to try the relays, but I wouldn't mind having a spare ECU anyway.

[alliedmotors Member Find all posts View Profile Close alliedmotors]

Re: Part # for AF ECU

I couldn't see the relays...just what has to be removed to get to them?

[siai47 Guru Find all posts View Profile Close siai47]

Re: Part # for AF ECU

Remove the drivers side headlight assembly. You need to remove the cover that goes between the grille and the radiator support that is held in by a half a dozen push pins. Then remove the two bolts holding in the headlamp assembly. Lift the whole assembly out. (there is a locating pin on the bottom that needs to clear the sheet metal mount to remove it) The relays are on a bracket just above the ECU. The easiest way to troubleshoot the relays is to buy a new one and subsitute it one at a time for each of the originals and see if that solves your problem. The relays are common and can be found at any auto parts store.

[ninjabluedog Member Find all posts View Profile Close ninjabluedog]

Re: Part # for AF ECU

Where are you able to get these old parts? I have a Chevy 1500 with a broken CNG sender switch (part number 16077). I have been told that they are impossible to get a hold of. Any suggestions?

[Insight Member Find all posts View Profile Close Insight]

Re: Part # for AF ECU

My 2002 Cavalier has an IMPCO AF ECU with part number 52371446 that functions when temperature is below ~55 F. I am looking for a replacement.

[catfish Member Find all posts View Profile Close catfish]

Re: Part # for AF ECU

So when are these ECU's going out on you guys. Is this based on mileage, years, or just whenever they see fit?

Also why are these so hard to find?

[siai47 Guru Find all posts View Profile Close siai47]

Re: Part # for AF ECU

They are not that hard to find. There is one on E-Bay right now. Take a look at it and you will see one of the problems that can happen to the ECU. Due to it's placement behind the headlight, they are subject to corrosion damage. If you are interested, ask the seller what the part number is on the ECU he has--I have listed superseded part numbers earlier on this thread. Worst case, the ECU will need to be reflashed (by a GM dealer) to work with your vehicle, however you might be able to plug it right in. It's pretty rare that they fail and I would make sure the one on the car you have is not getting corroded. If it is, clean it up and put some paint on it. If it does fail, just watch E-bay or see if someone on this site has one. The most likely failure on your car is not the ECU but the GMS/MCV. That's the part I would have in stock .

[catfish Member Find all posts View Profile Close catfish]

Re: Part # for AF ECU

They are not that hard to find. There is one on E-Bay right now. Take a look at it and you will see one of the problems that can happen to the ECU. Due to it's placement behind the headlight, they are subject to corrosion damage. If you are interested, ask the seller what the part number is on the ECU he has--I have listed superseded part numbers earlier on this thread. Worst case, the ECU will need to be reflashed (by a GM dealer) to work with your vehicle, however you might be able to plug it right in. It's pretty rare that they fail and I would make sure the one on the car you have is not getting corroded. If it it up and put some paint on it. If it does fail, just watch E-bay or see if someone on this site has one. The most likely failure on your car is not the ECU but the GMS/MCV. That's the part I would have in stock .

Ok so when does the GMS/MCV usually go out? Are they expensive?

[siai47 Guru Find all posts View Profile Close siai47]

Re: Part # for AF ECU

Nobody can tell when something is going to "fail". However, if I had one extra, sometimes hard to get, part in stock, it would be the GMS/MCV. This is the little rectangular box on top of the engine that says "GM alternative fuels" on it. What starts to flake out in this assembly is the GMS side not the MCV. They are joined at the hip and really are one thing that can't easily be seperated. The GMS (gas mass sensor) is a lot like a mass airflow sensor used in almost everything on wheels, except the CNG sensor assembly and its associated electronics are like nothing else on wheels. I have picked up a couple on E-bay for about $200 each. Both worked when tested. As these cars get older, many are being scrapped and the CNG parts show up from time to time. Keep an eye out and when one shows up, snap it up and put it on the shelf for a rainy day.

[Tommy Member Find all posts View Profile Close Tommy]

Re: Part # for AF ECU

There's a used AF ECU currenty (Nov 14, 2011) listed on ebay. Item number 320794212526.