Well I just bought a 98 cavalier z24 convertible from a lot in a town i was working in a few days ago, I have since come home and the drive is about 3 hours, so i prefer not to try taking it back if i can avoid that. Car had ridiculously low millage, 33,100 for being 13 years old. The odometer is digital which tells me it was manufactured in the later part of 98 since my previous cavy (also a 98) had a ticker style. Anyhow I drove the car back to my hotel (about an hour and a half) and around town for 2 nights, then the check engine light came on. not being near an autozone or similiar i just basically said oh @!#$ ill have to deal with it when i get home. I started the car 3 days later.. no light, drove it home (4-5 hours from hotel) no light, drove it for 2 days, no light. This morning i start her up, and lights back, take it to advanced auto, they put the handheld on it and it came back p1621. The kid with gauged ears who looked to be 20 said he had no idea what it meant. not knocking him as im only 24 and have gauged ears too lol, but anyhow, when he read it, it cleared it. A quick google search tells me this code is something internal in the PCM, something about checksums not matching, and basically extremely bad news and I probably need a new computer. I know a dealership is going to rape me with prices and things to change, but other than this code, the car runs fantastic, top is in great shape, solid body, etc. Can someone please tell me if i should be having a heart attack or not? btw auto tranny. 2.4 LD9 engine. I guess the final bit of information i can offer is the car doesnt appear to be doing anything wrong that would warrent this code, shifts fine, no ticks, etc...

I checked the diagnostic table for this code...never seen one so short....needs pcm.

i think you can reprogram a used pcm; putting your cars vin into the uesed module. i have done it....to a 01 grand am if i remember correctly.

the theft deterent will need to be reprogrammed and the crankshaft position learn redone. the dealer would probably charge 2hours labour for replacement and programming.

so basically i do need a new pcm... and a dealership has to do it??

Yup. You can't just program the pcm yourself. It's software no one but the dealership has. I'd take it back to where.yoy got it and tell them to fix it. Should be under a warranty.

im trying to avoid that as its going to be about a 4hour drive one way and id need a day off of work and however long to have them fix it. Some mechanically inclined buddys told me i can pick up a computer from a yard for about 100bucks and as long as its from a 98 cavalier z24 auto, i can just sorta slap it in. Any ideas as to whether thats accurate or not?

You could pull a ECU from the junkyard and use it. Just make sure it it a 97-98 2.4 auto. That would likely be the best bet.

Also if the car is running fine you could ignore and drive.



FU Tuning

Also if its checksums its just the computers internal records keeping basically. The computer things some part of the software is a little messed up. I think it only checks it when it first boots so if the code comes on shutting the car off for more than a minute and turning it back on should clear it. At worse I would say you would need to pay the dealer for an hour of labor to re-flash that same computer with the tech 2 scanner.


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if you want to save the ecm install labour just be aware that you may be towing it to the dealer if the relearn doesn't work. after the ecm is changed out the car won't start. So if your prepared to install it yourself you will have to do the vtd relearn. I think the procedure is to leave the key on engine off for 10min untill the security light stops flashing. turn the key off, wait ten seconds and the start the car.

Ya, they could probably just reflash the computer, the dealership up here in Cleveland, charged like 50 bucks for a reflash. So its not that expensive.

I guess Ill take it to the local chevy dealer and ask if they can reflash the ECM then. thanks for the replys, ill post back when i know whats going on.

If the dealer is a rip off, why not buy your own Tech II, and all the software and program it yourself? You can buy a one day subscription to GM factory service info

Otheriwse STFU, dealers like anyone else are there to make money. They dont make near as much as you thin, you have no idea what the tooling cost that the dealer has to pay for really cost. I've worked at tons of dealer and seen it firsthand.


- 2004 Cavalier - 124k, owned since new

Rob wrote:If the dealer is a rip off, why not buy your own Tech II, and all the software and program it yourself? You can buy a one day subscription to GM factory service info

Otheriwse STFU, dealers like anyone else are there to make money. They dont make near as much as you thin, you have no idea what the tooling cost that the dealer has to pay for really cost. I've worked at tons of dealer and seen it firsthand.

You out of all people should understand going to the dealer on a car this old IS a rip off. Quite frankly, there is no money in repairing old vehicles from years ago. Manufacturers have to jack the prices to deter 3rd and 4th owners from coming back to the dealer and requiring old technology and parts that no longer have suppliers. Its not a sound business decision.

So coming from the manufacturer (corporate) side, The dealer in this case IS a ripoff...



Buildin' n' Boostin for 08' - Alex Richards

Alex Richards wrote:

Rob wrote:If the dealer is a rip off, why not buy your own Tech II, and all the software and program it yourself? You can buy a one day subscription to GM factory service info

Otheriwse STFU, dealers like anyone else are there to make money. They dont make near as much as you thin, you have no idea what the tooling cost that the dealer has to pay for really cost. I've worked at tons of dealer and seen it firsthand.

You out of all people should understand going to the dealer on a car this old IS a rip off. Quite frankly, there is no money in repairing old vehicles from years ago. Manufacturers have to jack the prices to deter 3rd and 4th owners from coming back to the dealer and requiring old technology and parts that no longer have suppliers. Its not a sound business decision.

So coming from the manufacturer (corporate) side, The dealer in this case IS a ripoff...

Incorrect.

They still have the old technology. IThe Chrysler dealer I was at last still had all the older scan tools to do cars from the 90s.


So while the bill might be expensive for an older vehicle, according to the OP the car is in great shape. So once he replace the PCM, he will a really decent working vehicle.

What I was going to suggest until I read the OPs comment, is the fact that PCM may not even need programming.

I know Chryslers from that era did not as long as you got the same, year, trans, engine etc.


- 2004 Cavalier - 124k, owned since new

Wow guys im not trying to start a war, just looking for some advice. The dealership however says that if i am indeed looking at a reflash, that its going to run me in the range of 150$, however that was after the 80 diagnostic since they can not take autozones word for it. My buddys got one of those computer scanner things too, i think ill have him hook it up and see what pops to be absolutely positive. (at current typing, there is no light) but im not going to spend 230 to have them "fix" the old computer when autozone sells new ones for 125. Last question for this post, someone told me that I could try to reset the computer by pulling the battery cables for like 3 days and not running the car (which i can do since i really only drive it on weekends due to work) then hook it back up, and the computer will "learn" all its correct values after a day or two. THis seem accurate to anyone?

Man...I dunno, if I ever you, just take it back to that dealership you bought it at and have them pay for it all, it has to have a warranty and it won't cost you anything.

no warranty on the car. the lot didnt offer them, and the dealership (used car lot) is like 5hours away from me. this really doesnt seem like a big project my local automotive buddys are telling me maybe 10min to put a new pcm in, and about 125 for it from autozone. and the relearn takes 30min according to other sites ive read, am i missing something here that is going to be over my head? Id really not like to take it back as I already have my garage bay leased to start my modification project. If i can do some computer work now i will. Just trying to get all my information straight, yano?

twizt3d wrote:no warranty on the car. the lot didnt offer them, and the dealership (used car lot) is like 5hours away from me. this really doesnt seem like a big project my local automotive buddys are telling me maybe 10min to put a new pcm in, and about 125 for it from autozone. and the relearn takes 30min according to other sites ive read, am i missing something here that is going to be over my head? Id really not like to take it back as I already have my garage bay leased to start my modification project. If i can do some computer work now i will. Just trying to get all my information straight, yano?

There is no relearn the pcm does with regards to parameters... The PCM if you buy it from Autozone will be programmed based on your VIN number to your vehicle and will install relatively easily if you do it yourself. Pull off bumper, disconnect connectors, drop old out, drop new in, drive car back to autozone and get your core credit back.

The only adaptation a PCM will do is in regards to fuel trims... and that has nothing to do with how you drive or what your car has in it options wise.



Buildin' n' Boostin for 08' - Alex Richards

so whats with this turn key to acc for 10 min, then off, then crank, then off then crank interval thing i keep reading about? something to do with the theft deterrent system... and i knew they would need my vin, they told me that over the phone.

The PASSLOCK lock cylinder
The instrument cluster
The powertrain control module (PCM)

If you replace any of the above components, the system will enter the long tamper mode. If the system enters the long tamper mode, ensure that the system completes a long tamper mode cycle. During the long tamper mode cycle, the THEFT indicator will flash for the full 10 minutes. The instrument cluster and the PCM require the full 10 minutes in order to complete the learn cycle. Ensure that the ignition switch remains in RUN until the indicator stops flashing. If you turn the ignition switch before the indicator stops flashing, ensure that you repeat the long tamper cycle from the beginning

After shutting the ignition off you should be able to start the car once your done letting it flash.




Buildin' n' Boostin for 08' - Alex Richards

Just a quick update, I got my hands on a cheap code scanner to keep, the light has been off for a while now anyway, but it does pop back on once in a while. I found someone that can do a GM Reflash locally, and cheap. So im going to give that a shot first. I did kill the battery for a few days to reset the computer and like i said havnt seen the code in a few days. So maybe the PCM isnt shot? Opinions on whether i should just bite it and put a new one in anyway?