How do I find the right PCM?

[NASFD35]

Ok, as some of you may know, I’ve had numerous problems with my 6.5. Many DTC have come back when a scan was conducted. The latest problem is a throttle problem. When I’m driving, I’m able to accelerate, but when I attempt to cruise the truck “bucks”. I think all of my problems are due to the PCM getting wet. When it rains really hard, water runs down the inside of the right windshield, down the inside firewall, and onto the floorboard. My plan was to get a cheap PCM from the junkyard, replace it and see if the problems duplicate. Now, my problem….. My mechanic (he is also “stumped” as to the source of the problems) informed me that I have a performance chip in the truck. How do I find a stock chip? And the PCM from the junkyard has a chip that is light blue and says Blue on the bottom. Could this be the stock chip? The PCM from the junkyard will not work in my truck (wrong plugs).
My VIN number is 2GCEK19S9S1136645 if that’ll help.

[JohnC]

Get one from the same year (must be Diesel) and put your chip in it.

I don't speak fluent VIN, but if you had the year and model it would help...

[a5150nut]

IIRC, only 94 & 95 have removable chips. 96 and up you reprogram or replace the entire box.

[Robyn]

That is correct
94-95 use a removable PROM and then 96 on had the box with all the goodies in the box.

The ECM you use must be from the same year, same tranny, same engine, same GVW and same options (AC and such)

There is/was a paper sticker on the ECM Box that has leters and numbers. this is the ECM code indentifier.

In short you just can't take any ECM and plug it in.

A stick shift Equiped trucks ECM will not work in a truck with an auto tranny. The ECM from a 1500 truck will not work in the 2500

Equipment and the emissions setting all play a part in this complicated game.

Good luck and keep us posted

Robyn

[JohnC]

The "Blue" chip is 94-95. Any Diesel PCM from the right year should work as long as the chip is right. I ran one from a 'burban with an "F" pickup chip in my e-cab "S". Worked fine...

[Robyn]

John
That info is good to know.

I was always under the impression that everything had to match in order for the ECM to interchange.

The info that the dealers peddle is not always right me thinks.

Back to the thread subject.

I would be spending some time and fixing the water leak issue.

Water getting into the electronics will foul that stuff reeeeeeeeeeeeeeeeeal quick.

If you live in salt country, the road spray that hits the windshield will in some diluted form find its way in through the leak too.

Salt is a real issue if it gets into the electronics.

Good luck

Robyn

[oilburnertoo]

There is a 4 letter code on a paper tag on the ECM and also on the chip , such as "BPAA" or some such. This is what has to match as that is the code for auto or manual trans , egr , A/C , etc. This is for '94-'95 only, '96 up needs the whole PCM sent in to be reprogrammed as has been posted already. The letters "BLUE" are so the chip can be easily oriented in the socket one way only.

[JohnC]

NASFD35 didn't give the year; I know it's buried in the VIN, but I'm too lazy to figure it out. Anyhow, my 93, and 94's are the same, has a problem with the area under the vent below the windshield. The "floor" had 2 raised edge holes that would leak tons of water if the vent drains in each outer corner got plugged, which happened every spring when the oaks pollinated. My '93 had no PCM, but the carpets sure stunk...

I don't think it applies to '95s as mine never had the same problem.

[More Power]

Have you verified that the PCM actually got wet? It's situated in a position that should prevent it from getting wet due to a windshield leak - or even a big spill on the dash.

Jim

[THEFERMANATOR]

The chip is what dictates the options of the truck. ALL 95 6.5 ECM's are the same and interchange so long as you put the correct PROM CHIP in it. And I know a 95 ECM WILL run in a 94 as I gave my old ECM from my 95 2500 BURB to a friend with a 94 2500 light duty(6 lug truck) and it ran fine with the exception of codes due to the fact he didn't remove the EGR set-up. He later removed the EGR solonoids and hooked the hoses up like an F engine and said it ran fine(except for the idle flare which is why I got a new ECM in the first place). Just make sure it is a 6.5 ECM for a DS4 truck as the DB2 vans PCM's was different.

[NASFD35]

Ok. I think I’m getting slightly confused. So any PCM from a `95 will work? As long as the 4 digit codes match? Is that correct?
More Power….How would I confirm that the PCM had gotten wet? I’ve ruled out various different issues and my problems seem to get worse after rain. I’m running out of options. The current problem is : (1) when the truck starts it revs up to about 4000rpm the settles down. This all happens without touching the accelerator pedal. (2) When the truck does settle down to an idle it’s very erratic. (3) When I drive the truck I can only accelerate or coast, theirs is no middle…..no “cruising”. May of the problems are similar to the fella in this link. http://www.thedieselpageforums.com/tdpforum/showthread.php?t=36758. I'm hoping that it's not the pump.
John C….sorry, the truck is a 95.

[THEFERMANATOR]

Any 95 6.5 ECM for a DS4 truck will work. The 4 digit code is for the chip which you can swap out from your old ECM or get the upgraded one from GM that address's shift issues and also changes theway the turbo boosts at cruise(I went from 2.2-2.5 at 65 MPH cruising down to 1.2-1.7 with the chip upgrade, milage also went up by about 1-1.5 MPG's).

[NASFD35]

I’m still unsure which route I should take. As Paul Harvey would say, here’s the rest of the story…(and more questions to follow).
The problems started after I disconnected the batteries to replace my starter. The problems are; (1) the I start the truck the RPM’s rev up to about 3-4K, then the truck settles into an erratic idle. (2) when I can get the truck to drive, I can accelerate or decelerate, there’s no in between to let me cruise. Now the newest problem (3) the truck wouldn’t go into reverse for a bit, now it won’t go into drive.
Now the questions;
If I disconnected the batteries, do I have to do anything specific to “reboot” the PCM?
What’s the likelihood that the problem is the PCM?
What actually controls things, the chip or the PCM? The kid that had the truck before me put a performance chip into the truck, so I’m not sure if that’s the problem.
If I change the computer, does the new one have to be “flashed”?
Any and all help is appreciated. I’m starting to lose my mind.

[JohnC]

The chip has all the instructions. The PCM minus the chip is just the interface to the truck.

First thing I'd do is go over all the grounds on the truck and the positive battery connections. Check especially the cluster of ground wires on the passenger's side rear of the intake manifold. These are for the PCM and all sensors. Also check the ground on the top cover of the injection pump and the double positive connection on the passenger's battery. Probably be a good idea to look at the positive feed to the truck from the starter, if there is one (I forget...).

The PCM does not need to reboot, but at this point it couldn't hurt to disconnect both batteries and let it sit for an hour or two, after checking things, to give it a clean start.

If you change the PCM you want to do "TDC offset learn" but it'll run without doing that.

[NASFD35]

Well……It’s officially NOT the computer. I found another K1500 for sale, bought it (or should I say I stole it for $1800) and switched the computers. The problem was identical. Any other thoughts? I think the old truck is going to become a parts truck.

[JohnC]

Well……It’s officially NOT the computer.

Have you put a scanner on it? Look at solenoid closure time. Also, run through the "stalling" troubleshooting in the Tech forum. My guess it's either the wiring or the injection pump. You could try dosing the heck out of it with fuel conditioner to see if there is an improvement. Also, what resistor is on the FSD? Too high a number can make it real touchy.