ECU module replacement

[old n' slow]

We own 2 2004 Aveo's since 2004 and I've maintained them myself . One automatic with 174K miles and a stick shift with 100K miles . Today I'm finally stumped with a check engine light problem . After doing everything else , I think it might be the control unit ( ECU ) but before I buy a used one I'd like to ask .

Will a used ECU from a running ( junked ) car just "plug & play' ( everything matches , AC Delco numbers , the right year & transmission , etc ) OR WILL IT HAVE TO BE REPROGRAMMED/FLASHED simply because it's coming from another vehicle ?

Thanks in advance for any help . old n' slow

[petrified.rabbit]

this is hit and miss. I tried it, it seemed to work. But I cannot say I ran it long or at all really. Just wanted to see if it would start.

I have thought about it for chipping the car, but then it would be reprogrammed anyhow.

When I went to the dealer, they insisted the ECU comes without a base program. Which does not make sense to me either.
I would think if you match up all the options, that it should work as long as you do not have IMMO, or the key sensors. I do not know where those are programmed into the system, but my car does not have that system in it. I looked.

[petrified.rabbit]

In fact since you have two of the same car. (minus transmission) I would switch them and see what happens. Since the car has a separate transmission control module it should work, but would not be 100%. It would let you know the answer though.

Just be aware that with either answer, it seems the ecu will "forget" some of the idle settings, etc when it loses power. And you might need to do a relearn procedure.

[old n' slow]

I did think about doing the switch but was afraid I might wind up with two "deprogrammed" ECU'S . The used ones are only in the $60 range and the local dealer ( I was told by a friend ) wants about $700 including programming . Thank you very much for sharing .
P.S. I know I don't have key sensors and I will have to google IMMO tomorrow to find out what it means : ) Goodnight .

[06T200]

Just FYI, you can find new OE GM ECM's at Rockauto for less than $350 shipped to you for the 2004MY. A local GM dealer charged me $109 (one hour book labor) to program and install it, so $700 is a stretch IMO. But used is definitely an option. Let us know how you fare with the swap.

[old n' slow]

Just FYI, you can find new OE GM ECM's at Rockauto for less than $350 shipped to you for the 2004MY. A local GM dealer charged me $109 (one hour book labor) to program and install it, so $700 is a stretch IMO. But used is definitely an option. Let us know how you fare with the swap.

I called two dealers both say reprogramming / flashing a used ECU ( same year , same trans, etc) is doubtful ( one said 80% failure rate ) , then I look on ebay and find a reputable seller charging $255. for a used ECU reprogrammed/flashed and guaranteed to work as long as I provide all info ( VID , trans, etc)

Interesting how one seller can reprogram/flash a used ECU and dealers say probably not . Someone is incompetent or not telling the truth .

Today I hopefully find out if all things point to a bad ECU . Then it's decision time .

[06T200]

Makes sense. Anyone with possession of a tech2, 2004 or newer tis2data CD, MDI, etc. can do the job, been there done that, the problem is most DIY mechanics don't just have these tools lying around lol Let's hope this changes in time.

[old n' slow]

I'll have to take your work on it since it's all beyond my skill level , but are the dealers incompetent or lying just to sell new $500 ECU's plus $100-$150 reprogramming & installation labor ????

Used wrecking yard ECU's go for $50 & flashing should be $100. Quite a difference .

[06T200]

FWIW: There are a few GM TIS bulletins out there about failures of 'in car' J2534 flash loads, and them failing in process. So I imagine it's a case by case type deal, but they nail ya in labor either way. It is truly amazing how much money GM has milked out of a closed technology that is going on 3 decades old, and is still alleged to be closed to the public, even after accepting public revenue.

[06T200]

> but are the dealers incompetent or lying just to sell new $500 ECU's plus $100-$150 reprogramming & installation labor ????

I don't think they like to use the word 'lying', too blunt. Deceptive 'marketing' sounds so much more warm and cozy LOL

Probably a combination of both to be honest. and very frustrating to say the least.