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 PCM ECM ECU computer bad on 1995 SC Riviera?

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al_roethlisberger
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al_roethlisberger
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PCM ECM ECU computer bad on 1995 SC Riviera? - Page 2 Empty
PostSubject: Re: PCM ECM ECU computer bad on 1995 SC Riviera?   PCM ECM ECU computer bad on 1995 SC Riviera? - Page 2 EmptyTue Aug 26, 2014 9:13 pm


Thanks for all the suggestions, sounds like I have some more testing opportunities smile

I'll let you know what I find.

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al_roethlisberger
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PCM ECM ECU computer bad on 1995 SC Riviera? - Page 2 Empty
PostSubject: Re: PCM ECM ECU computer bad on 1995 SC Riviera?   PCM ECM ECU computer bad on 1995 SC Riviera? - Page 2 EmptyFri Aug 29, 2014 5:28 pm


Can anyone confirm on what other GM models the PCM is shared with the 1995 SC Riviera?

Hoping to go to the pick/pull this weekend and pickup one or two to test.

Thanks
Al
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PCM ECM ECU computer bad on 1995 SC Riviera? - Page 2 Empty
PostSubject: Re: PCM ECM ECU computer bad on 1995 SC Riviera?   PCM ECM ECU computer bad on 1995 SC Riviera? - Page 2 EmptyFri Aug 29, 2014 6:04 pm


Here is what I get from Rock Auto:

ACDELCO Part # 16183247

Buick Lesabre 1994-1995
Buick Park Avenue 1994-1995
Buick Riviera 1995
Chevrolet Lumina APV 1994-1995
Oldsmobile 88 1994-1995
Oldsmobile 98 1994-1995
Oldsmobile Silhouette 1994-1995
Pontiac Bonneville 1994-1995
Pontiac Tran Sport 1994-1995

Look correct?

Thanks
Al
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PCM ECM ECU computer bad on 1995 SC Riviera? - Page 2 Empty
PostSubject: Re: PCM ECM ECU computer bad on 1995 SC Riviera?   PCM ECM ECU computer bad on 1995 SC Riviera? - Page 2 EmptyFri Aug 29, 2014 6:13 pm


One other question, if I find another PCM or buy a refurb unit and change over the PROM... will the PCM operate just fine (and the car run and operate normally) or am I going to have to have some sensors, security, other? reset by a technician with factory tech tool software?

Wasn't sure if this generation of PCM was pretty "dumb" and the PROM carried over all the vehicle specific information and settings such that just swapping it out was a simple 1:1 swap affair (hope so!)

Thanks
Al
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PCM ECM ECU computer bad on 1995 SC Riviera? - Page 2 Empty
PostSubject: Re: PCM ECM ECU computer bad on 1995 SC Riviera?   PCM ECM ECU computer bad on 1995 SC Riviera? - Page 2 EmptySat Aug 30, 2014 5:00 pm


Well, LKQ was having a 1/2 price "sale" today (funny, but true) so I got two PCMs and both happen to be refurb units so maybe that is good news.

I'll pop one in after swapping over the PROM and see what happens.

BTW, found two other threads here that may be useful for anyone else researching this issue for the SC Series 1 cars. Based on the thread below, it appears there is no programming needed, and one just pops out the PROM and installs. So I'll give that a try.

https://rivperformance.editboard.com/t6103-where-is-the-pcm-located-in-1995-buick-riviera

Another helpful thread:

https://rivperformance.editboard.com/t10487-write-up-reading-editing-and-burning-chips-for-a-series-1-l67




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PCM ECM ECU computer bad on 1995 SC Riviera? - Page 2 Empty
PostSubject: Re: PCM ECM ECU computer bad on 1995 SC Riviera?   PCM ECM ECU computer bad on 1995 SC Riviera? - Page 2 EmptySat Aug 30, 2014 6:53 pm

OK, too soon to declare victory, but the car does run and accelerates normally now.  Hopefully that is not a fluke!  wink


So, some answers:

1)  Yes, any of the models above exchange the same PCM as the 95 Riviera.
2)  Yes, it is simply a plug-and-play change, just swapping over the PROM.  No programming/reprogramming required.
3)  It is literally a 10 minute job of removing two screws to drop the under dash panel, unplug the three color coded harnesses, move the plastic clips to the side, and the PCM just slides out, maybe 15 if you take your time.  Of course one should disconnect the battery during this process.
4) Reverse process to reinstall (after swapping the blue PROM from inside the case)

So, some interesting discoveries.

I pulled two PCM's from the yard, one from a Lesabre and one from a Bonneville.  Both turned out to be remanufactured units.  When I pulled the PCM from the Riviera, guess what... it too was remanufactured.

After doing a little more Googling and reading about this series PCM, it seems that the 95 units (and probably the 94 too) are failing relatively commonly.  And based on my discovery of 3 for 3 being reman units, I would tend to agree.

That leads one to wonder why.  Who knows.  But it is also interesting that there are so many reman units available, and affordable. I doubt they are replacing ICs, but instead are probably replacing something like a capactor(s), resistor or cold solder work and that stuff is cheap.

So I'm going to tear apart my 'broken' one and see what I find.  It would be interesting to discover that these are failing due to something as simple as that.  It could also be a transistor, which is harder to detect to some degree of course.  But I bet it's something like that.

Anyway, if your 95 starts going wacky in an odd way with no or weird codes that the seemingly appropriate repairs don't address... the PCM may be the issue.  I'd get a cheap one from a yard for $30-50 and see if that clears it up.

We'll have to drive it for a week or two before I'm convinced of course, but so far it seems to be acting more normal than it has for a long while.
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PCM ECM ECU computer bad on 1995 SC Riviera? - Page 2 Empty
PostSubject: Re: PCM ECM ECU computer bad on 1995 SC Riviera?   PCM ECM ECU computer bad on 1995 SC Riviera? - Page 2 EmptyTue May 01, 2018 11:58 pm

What ever happened with this issue, i have been experiencing the same problems with my 95 and it has spent the padt 6 months in and out of the shop.
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PCM ECM ECU computer bad on 1995 SC Riviera? - Page 2 Empty
PostSubject: Re: PCM ECM ECU computer bad on 1995 SC Riviera?   PCM ECM ECU computer bad on 1995 SC Riviera? - Page 2 EmptyWed May 02, 2018 8:23 am

ajgee2011 wrote:
What ever happened with this issue, i have been experiencing the same problems with my 95 and it has spent the past 6 months in and out of the shop.

If I were you I'd try it.
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LARRY70GS
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PCM ECM ECU computer bad on 1995 SC Riviera? - Page 2 Empty
PostSubject: Re: PCM ECM ECU computer bad on 1995 SC Riviera?   PCM ECM ECU computer bad on 1995 SC Riviera? - Page 2 EmptyWed May 02, 2018 1:30 pm

I just had to change my mass air flow sensor. It's amazing how that little part can affect how the engine runs. My car would start, but would not idle, and it would stall almost immediately. To test it, just unplug the electrical connection. If the car idles and runs, the MAF is the problem. What happens is the MAF tells the PCM there is a lot of air entering the engine, the PCM ramps up the fuel injection, and then the O2 sensor tells the PCM the engine is running rich so the PCM pulls fuel. Back and forth it goes and the engine goes schitzo.

_________________
98 Riviera SC3800  All stock except gutted air box.
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