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 "Bad" PCM?

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Sir Psycho Sexy
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PostSubject: "Bad" PCM?   Sat Oct 25, 2014 11:43 am

I have a suspicion that my PCM is bad. Maybe I'm crazy?

When I went to ZZP for my dyno tune, they told me that my PCM was bone stock, but I know for a fact that Abaddon tuned my car.

And now, my car feels exactly the same as before I got the tune.

Is it possible that a PCM won't stay tuned?

The part number for a 97 PCM is 16227797, and Morad has two PCMs with that number. He says one is from a Regal and one is from a Park Ave. Would either of these be ok to use, or does it need to be from a 97 Riviera?

Thanks for any help, and sorry for the n00by question.
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PostSubject: Re: "Bad" PCM?   Sat Oct 25, 2014 12:32 pm

I think there's a greater chance of "bad" ZZP or Abaddon tune here, than a faulty PCM. If you noticed obvious improvements from Abaddon's tune, then ZZP accessed the PCM and now it feels like the tune was lost, there are two likely scenarios:

1) ZZP accidentally erased your previous tune and stet back to stock. This isn't likely, but it's very possible.

2) Abaddon's tune didn't stick. For whatever reason, you thought the tune worked, but actually it didn't.

Your "improvements" could have been be imagined. It is very easy to assume something is "better" (or "worse") after letting someone tinker with the PCM. This is because, since you didn't actually perform the adjustments yourself, you don't know exactly what's been changed, and how the changes impact the performance of the car. Your brain is filling in the unknowns, some real and some fabricated.

Ever washed & waxed the car, vacuumed the interior, polished the wheels, then take her for a spin? I have to fight every ounce of my being not to believe the car's performance has improved! The effect is so convincing, but I know nothing has really changed except my perception.

But if you're sure something obviously changed, or you took some scans to show measured changes before and after the ZZP visit, you could have a valid case. The only way to know for sure is to have a 3rd party (yourself, Scott, or another RP member) access your PCM and see the current state of things, then compare to what Abaddon programmed. If if you know some of Abaddon's tune characteristics, you can do some tests to confirm if they are still there - example: shift points vs. RPM. TCC lock-up values, etc.

I have never heard of a PCM forgetting a tune, or just going "bad" for that matter. It's not like a PC where the program is saved on magnetic disk. The PCM uses flash memory, very robust. The program isn't highly complex either, and isn't difficult for the PCM to retain. It's possible a gamma ray burst came from outer space and fried your program back to stock - actually, that's not possible. If something like this happened, your PCM wouldn't work at all, car wouldn't run.

Whatever the case, I believe the fault lies in the tuning, not the hardware. Swapping PCMs probably won't fix.

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PostSubject: Re: "Bad" PCM?   Sat Oct 25, 2014 1:03 pm

I remember around this time last year I was coming home from school and went WOT, and I hit the speed governor, which I absolutely know for a fact Scott removed. That's when my suspicion starts, then I had Charlie scan my car with his HPT in the spring and it showed that I was ruinning REALLY rich, which would make sense if I'm running bigger injectors with a stock tune.
After I found out how poorly my car was running, I took it to zzp. The dyno sheets show that zzp did actually improve my car quite a bit, and the car felt a lot nicer. I know you acclimate to increased power, but it really feels like my car is back to how it was.
Scott used dhp and Charlie used hpt, so that's one variable gone.
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PostSubject: Re: "Bad" PCM?   Sat Oct 25, 2014 2:13 pm

I would just try to get a backup of your tune and keep monitoring everything. That way if you do lose it you can possibly figure out what caused you to lose it (disconnected battery, sitting for awhile, etc).
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PostSubject: Re: "Bad" PCM?   Sat Oct 25, 2014 2:22 pm

Does disconnecting the battery make you lose your tune? Sorry, I'm completely uneducated about this stuff right now. My alternator failed shortly aftaftergot my tune, so I guess that would make sense.

Any input on if the regal or park ave pcm would work?
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PostSubject: Re: "Bad" PCM?   Sat Oct 25, 2014 6:58 pm

I've heard of it happening before, but I can't say for certain if it does or not.
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PostSubject: Re: "Bad" PCM?   Sat Oct 25, 2014 8:55 pm

No, disconnecting battery doesn't cause a PCM tune to be lost. It does reset fuel trims, though.

PS - I didn't mean to imply ZZP's or Abaddon's tunes are "bad", just that it would be bad if either one didn't flash properly.

_________________
'98 SC Riviera 268k miles 298 HP/370 TQ 0-60: 5.79s ET: 13.97 @ 99.28 4087 lb 20.1 avg MPG Nelson Ledges Lap: 1:30
3.4" pulley AL104 plugs 180 t-stat FWI w/K&N 1.9:1 rockers OR pushrods LS6 valve springs SLP headers ZZP fuel rails
KYB GR2 struts MaxAir shocks Addco sway bars UMI bushings GM STB Enkei 18" EV5s w/ Dunlop DZ101s F-body calipers
EBC bluestuff/Hawk HP plus SS lines Brembo slotted discs DHP tuned Aeroforce Hidden Hitch


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PostSubject: Re: "Bad" PCM?   Sun Oct 26, 2014 2:53 am

Well, I bought that hp tuner that I posted about a while back, but I don't have a laptop right now. I'm hopefully picking up a laptop tomorrow, then I can get a better idea of what's going on. I was just thinking that I don't want to pay for the credits to unlock the pcm if I'm just going to have to replace it then pay again to unlock the new one too.
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PostSubject: Re: "Bad" PCM?   Mon Oct 27, 2014 9:01 am

I think you will be fine. get the HPT on your PC now while you wait for a laptop so you can play with other peoples BINs watch scans so youre ready to hit the ground running.
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PostSubject: Re: "Bad" PCM?   Mon Oct 27, 2014 9:16 am

I just read this. Weird. I remember you shot me a text about the Speed Limiter when it happened. I absolutely changed all kinds of stuffs. I think I still have the file too if you need it.

I'll do some digging around today, ask some questions and see if any of the vets here around the shop have ever encountered a resetting PCM.
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PostSubject: Re: "Bad" PCM?   Mon Oct 27, 2014 3:25 pm

Thanks Scott. I remember you told me that it's impossible for a PCM to revert back to the stock tune. I'm hoping to get the hpt going today and scan to see what's going on.
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PostSubject: Re: "Bad" PCM?   Mon Oct 27, 2014 3:38 pm

It pretty much IS impossible, but we've seen some WEIRD shit around here. With so many modules and data lines, really nothing is impossible....

Once the board gets flashed, that's it. It's burned into it. That's what makes no sense. I remember changing your trans, Injector flow rates, MAF table, etc. It was there. We went on the freeway and scanned. The damn tune was loaded!!!
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PostSubject: Re: "Bad" PCM?   Tue Oct 28, 2014 9:38 am

Sooooo, yeah. There's no way that we know of for a software burn to overwrite itself. We have absolutely no ideas how it could happen twice, let alone once. Anybody's guess is as good as mine.

I just opened the tune we did....On 8/25/13 @ 5:26pm is when we finished it. I looked, and the Injector flow rates are exactly how they needed to be (~244.47 ms/Gram), and the trans and everything else is changed. I still have the log of it as well.
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PostSubject: Re: "Bad" PCM?   Tue Oct 28, 2014 10:48 am

This is freaking me out... Should I just look for a 97 riv pcm to swap in?

Thanks for asking around and looking up that tune Scott.
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PostSubject: Re: "Bad" PCM?   Tue Oct 28, 2014 12:04 pm

Couldn't hurt to have an extra laying around to throw in if need be. They're pretty cheap now, so I would grab one. Does anyone know if the wiring is different between 96 and 97+ PCMs? I'm thinking about grabbing a 97+ one and just flashing my bin to it to see if HPTuners works because it doesn't work on 96 PCMs.
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PostSubject: Re: "Bad" PCM?   Tue Oct 28, 2014 12:31 pm

It has to be different. Remember, you have a completely different trans. Plus, the logic in a '96 seems primitive compared to a '97.

You want me to send you a '97 .bin file for you to compare?
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PostSubject: Re: "Bad" PCM?   Tue Oct 28, 2014 2:38 pm

I already have the 97 bin and know it's pretty different. I'm just wondering if the PCM itself can be swapped with a 96 bin on it.
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PostSubject: Re: "Bad" PCM?   Tue Oct 28, 2014 3:41 pm

Oh that's right....I sent you that, ha.

I guess the only real way to tell is to pull the connector end-view schematics and compare all the PCM terminals. Again, though, the trans is going to be the biggest issue.
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