16156395 ??

[JeepsAndGuns]

Just got back from visiting my family in VA over the holiday weekend. While on my way up there, I hit up the pull a part in knoxville tn. Looked up thei inventory and had a few I wanted to check out. I scored a pcm from a 95 c3500 dually truck that had (long since removed) a 454. All others were a bust.
Its a 6395 pcm, BCC BJKW, finally scored a 454 memcal!. I am very interested to see if the knock filter gets along with my 401 any better than the 350 knock filters do.

Well when wiping the dust off the pcm, I noticed something odd. The service number on it is 16156395. Something hit me as odd, but it didnt hit me right away. A quick check of bcc find, and the bin/defination section, shows 16196395. But this one is most definately 16156395. I searched that service number on this site and got no hits. I google searched it and got no hits, however if I google search 16196395 I get plenty of hits.
So what exactly do I have here? Some oddball pcm? I hooked it up to my test harness and tested it, it works fine. So whats with the one number difference? The BCC and memcal appear to be original to the pcm, as the bcc is printed on the label with the service number. BCC find says 16196395 when I search it.

[EagleMark]

Ive found a few replaced like that. I think it is just a new number for servive when and ECM/PCM fails the dealer puts in a new one with old Memcal/Chip.

[JeepsAndGuns]

Do they print the service number/bcc sticker at the dealership? This one has the bcc on the sticker. I didnt think the reman/replacement ones had the bcc on them.

[EagleMark]

That was just one scenario, but all you have is a differant number PCM. It's still the same thing.

[RobertISaar]

pop it open and put an opened 16196395 next to it for comparison?

[JeepsAndGuns]

I do not have a 16196395 to compare to. All I have is a couple 7427's and a 8625.

I sodered in the mpfi jumper wire and gave the 454 memcal a try today. No luck. Still the same stupid crazy number of knock counts as I get with the 350 memcals/knock filters. My next try will be to add one of those brass elbows and try that.

[EagleMark]

Might be hard to see some subtle differences? Could see if anything noticable to a 16197427. So far 16197427 PCM has worked for all other PCMs I've tried...

[JeepsAndGuns]

So what exactly are the differences between the service numbers of this series of pcm's? 8625, 6395, 7427, etc..
And why would this 95 model truck have this pcm instead of a 7427? This is the first 94-95 truck/suv I have seen that did not hve a 7427.
I'll open it up this afternoon when I get home from work and set it next to a 7427 and see if I see any differences.

[1project2many]

That family of pcm went through several fairly rapid part number changes early on. There were some bulletins back in the day that addressed issues where the dealer parts dept. ordered one number and another was sent instead. Usually when this happened it suggested a production change due to a defect or flaw, although GM usually didn't give details. 7427 is the last number IIIRC.

The label with the BCC indicates that is a factory supplied pcm. 16156395 is probably what's called a GM "internal number". It's the number called out in build drawings and engineering documents for use inside GM but it's not the number used by GM SPO for replacement parts.

[JeepsAndGuns]

So this pcm was not supposed to make it out of the factory? Or you think it maybe had a flaw and they changed maybe one tiny part of it and changed the number to 16196395?


I opened it and a 7427 up and put them side my side. No major changes, it all looks the same. Only differences I see are some of the small numbers on some of the chips (the large numbers all mach, but theres also a 2nd set of smaller numbers thats different) There are also a few random small do-hickeys on the board that are different colors (resistors, capicators, whatevers?..lol)
Anyone have a 16196395? I can takes pics if anyone wants to compare them.

[RobertISaar]

being nearly identical is not surprising. small changes on the ICs might be date code differences or something similar.

[JeepsAndGuns]

I opened up the 16168625 pcm I have and compared it to them as well. All the small little parts that were different colors between the 6395 and 7427, were the same between the 6395 and 8625. Board and everything else was all laid out just the same on the 8625, only big difference in the 8625 was it had two extra round red disc thingys. The 6395 and 7427 had the spots on the borad for them, but nothing was in them.

[RobertISaar]

about the size of a quarter? maybe looks like it had a wire running through it diagonally?

those would be varistors, used for protection against abnormally high voltages.

[JeepsAndGuns]

No, these were WAY smaller than a quater, maybe 1/2 in or smaller, had two wires coming out of them. Looking at pics, I think they are disk type capacitors.

[RobertISaar]

could be, if any codes were visible on them, it could be 100% determined.