PCM failure?????

[BIGSTICK]

About 2 months ago my truck started missing at stop lights but would smooth out after takeoff and it wasn't regularly I took it to the dealer and they said unless it was doing it when I brought it in, they couldn't help me. So I waited for 2 weeks until it did it again and this time I used the trust Onstar and they diagnosed it saying it was a number 8 cylinder failure. So I went to the dealer and told them what Onstar said and that they had stored it in the system and after arguing with the service manager about it(he said that there was no way Onstar would do that, in which I said that he needed to do some research on Onstar). After a few minutes, he ate his words when lo and behold, their diesel mechanic prooved him wrong. Anyways the wiring harness to the number 8 cylinder was bad so they replaced it and the fuel module. The truck ran great until 2 weeks ago when I was on vacation and it started it again only worse this time it was bucking and stuttering at 70 on the highway. It lasted about 5 minutes then went back to normal. Did not come back until last Saturday. It was doing it all weekend for about 90% of the time. So I used Onstar again and they said PCM failure. On tuesday I took it to the dealer and they verified it and ordered one thank god it was covered under a 80,000 mile emissions warranty b/c it would've been 1000-1500 for a new one. They finally got the part yesterday but said my batteries were drained and they had to charge them overnight b/c they can't reprogram the new one unless they batteries are at 12.7-13.5 volts. So here I sit while they are charging my batteries. Oh and they have no idea what made the PCM go bad. Has anyone else had this kind of problem? I do have the Hot juice w/ attitude so I called Edge and they said no way possible for the Juice to cause it b/c it hooks in after the PCM. Hopefully someone can shed some light on this for me.
Thanks,
Randy

[More Power]

I'd run the truck without any performance modules for a period of time to verify that the problem doesn't return. ECM's rarely go bad, but....

Incidentally, ECM's from a salvage center are about $200 each. I'm running both an ECM and a TCM in our project truck that was obtained from a nationally operated salvage center. They work just fine, and have been reprogrammed at the dealership - updating them with the VIN and current programming for the truck's current configuration.

I'd be curious to learn how your batteries went dead...

MP

[BIGSTICK]

Well now the dealer tells me that the new pcm they tried to program is already bad. ARGH!!!!!!!!!!! WHY ME!?!?!?!?!? So they won't be able to get another one till monday. Thankfully due to my unhappiness, they are going to set me up with a loaner. They still have no idea what made it go bad and he told me that these things go bad in vehicles across the board fairly frequently. Say what!?!? That is why they are warrantied to 80,000 miles now, and they can't say whether or not the new one will survive. Maybe I should have rebuilt my totalled Dodge........

[BIGSTICK]

Well, the dealer recieved another PCM today and it would not program either. The called tech support at GM and was told that it was another bad PCM but my service manager finds it hard to believe that he has gotten 2 PCM's bad out of the box now. So they are doing some investigating in the electrical system. At least they got me in an '04 Silverado ex-cab 4x4 until they get it fixed.

[BIGSTICK]

Well the dealer found some fuses/relays in the main fuse block not getting power caused by a bad BUSS strip and wiring harness so they replaced those parts today and PCM still will not program so GM Tech Assistance told them to replace the PCM again b/c the 2nd new one was alos a bad one. The service manager is as dumbfounded as I am at this point. OH and get this, they still have no idea what caused all this mess. Next tuesday will be 2 weeks that they have had the truck and for the same problem for the 2nd time........LOL.

[BIGSTICK]

Well the dealer got the 3rd PCM today and it wouldn't program either. GM Tech Support says still yet another bad PCM. So they are getting another one tomorrow.

[NFLDMAX]

I can't believe they keep replacing the PCM's. 3 bad ones in a row :confused:

[heartbeatcanada]

I'd find a new dealer cause these guys are a joke. But then again, gm is just as dumb, IF this is what they are telling the dealer to do. There is obviously another problem than the pcm. I've swapped more pcms into my truck than a hooker has partners and have never ever had one problem.

I'd start barkin at gm customer service and get things straightened out as its obvious they are clueless. It doesn't take a rocket scientist to figure out its not constantly bad pcms. :mad:

[heartbeatcanada]

Or the dealer does not know how to program the pcm and keeps f'n them up or installing it wrong. If thats the case its definetely time to find another dealer. If i can do it, anybody with half a brain can do it.

How are they bad pcms??? Will the truck not run after they install it??? Whats the symptoms???? Do they know that they have to do the theft deterent learn in??? I would assume they do, but then again, maybe they don't.

[BIGSTICK]

It is not the dealership's fault, and I know this b/c their diesel mechanic has his own D-max that is turned up. He knows what he is doing and at this point they have to follow GM Tech Support's orders although they are still going through almost every electrical device while waiting. If they put my original PCM in the truck runs but like ****. The 4 new ones they have tried will not program at all it gets to a certain point and then kicks them out. They also found out that the injection module isn't getting power and they are wondering how the truck ran when I took it in without power. They even tried to reprogram with an aftermarket programmer for ****s and grins. No one across the board has apparently had this problem either. It is not the dealership as me nor anyone I know has never had any problem with them they are very reputable in my area and their diesel mechanics are the best around. I am very happy with the dealer just not GM at this point.

[heartbeatcanada]

It sounds like theres a bad wire connection somewhere then. The only thing thats got me puzzled and most likely you too....is why does the truck still start with your old pcm and not any of the new ones :confused: if it was a bad connection somewhere you would think it wouldn't start with the old one too.

Don't take it as i was ragging on the dealer(though i re-read what i posted and it did seem harsh) sometimes little things like the learn in of the theft deterent or such can be overlooked so easily. I've been through some problems of my own, that some very reputable people in the know how department couldn't solve, yet my wife suggested something so simple and we laughed at her, but guess what she was right :eek: . We were so involved and thought it was so much more, that we were stuck looking "inside the box" instead of looking "outside the box" Thats all i was getting at.

I have never heard of this, and like i've said, i've had prolly over 20-30 pcm swaps in my truck testing tunes and not one problem.

[Kennedy]

Do you have any audio accessories installed like aftermarket XM etc?

I'd be looking at grounds, wires, and removing any odd accessories that may be on the Data Bus.

I believe the grounds behind the dash cluster are usual suspects, as well as the grounds to the block down near the crankcase.

[White Truck]

I am not surprised the truck won't start with any of the new PCMs. If the programming can't be completed, it lacks the security communication with the BCM, for starters.
JK has some good ideas, check those out, especially all block grounds. I would also look at all other modules to be sure they are communicating properly. You mentioned them charging your batteries in your 1st post, that's a critical step they are obviously aware of.
These comments concern me: "Well the dealer found some fuses/relays in the main fuse block not getting power caused by a bad BUSS strip and wiring harness so they replaced those parts today ------- They also found out that the injection module isn't getting power and they are wondering how the truck ran when I took it in without power."
Well, the engine won't run without power to the FICM. You still have a wire harness or junction block issue, if this is the case.


Dennis

[jbplock]

It would be interesting to see if one of these "bad" PCM's could be successfully programmed in another truck... If so it would point to a wiring problem ...

[BIGSTICK]

Well they did find a grounding problem yesterday and have the truck running and have been test driving it to see what happens. Here is the new problem though they have the old PCM in it and it programmed, updated and everything else needed to get it running. However, none of the 4 new PCM's will program and the whole problem in the beginning was a bad PCM so they don't want to give the truck back to me with my old PCM in it because of that being the initial problem. So they are driving it trying/hoping that it will reveal a problem so they can fix it. So why will the old PCM work but none of the new ones? 15 days and counting....

[Kennedy]

Could be that the partially completed programming locked them up...

[midwest]

I agree with John, unless you get a full download there is no operating system file and the pcm is dead.It can't be recovered in the field. It sure wouln't take me 4 pcms before I confirmed (voltage droped) all power and ground circuts. Serial comunication data bus circuts are also crutial.I'm not sure I believe your problem is a pcm in the first place.I believe if you find the problem the pcm will program also. I have never had to put in a pcm for any issues. I've seen several ficm's failures though.
Have you ever had any welding done on your truck for any reason.(exhaust,trailer hitch,body work)
This will usually damage the tcm first but the pcm can also be damaged but may not show up right away. Ign switches have also been an issue and can be verified in power mode with tech II.

[White Truck]

I don't have any reason to believe the orginal PCM was faulty in the 1st place with the wiring faults that have been identified so far.

Dennis

[BIGSTICK]

Yes I have welded on my truck but I am a welder by profession so, I have never done it with the batteries connected. Here is some interesting news, after testing with the old PCM yesterday, they recieved yet another new one. HOLY COW BATMAN!!!! It took a program however, the other ones still would not program so it looks like maybe Tech Support could have been partially right. Only time will tell if the problem is fixed. I am supposed to get the truck back at noon after they road test it with the new PCM. SO I guess maybe I will get my truck back with a lot of new parts and 20K more miles, lol....

[midwest]

Unhooking the battery does not save the pcm or bcm.They must be removed from the vehicles. There are several other paths to the pcm through the harness. On a gas vehicle the o2 senors are a direct path.Diesels can actually return to the FICM and pcm through grounds still conected. It is probably less safe to actually unhook the battery just by itself as the battery is a form of capacitor.
The BCM CAN NOT be grounded, thats why it is in the plastic case on the fan shroud. If you let the case ground during testing or whatever it will likely damage the BCM.

As for your pcm now programming,I believe it is because you fixed the communication problem(power,ground,serial data). The other pcm's were good pcm's till the programming failed.Once this happens it's done and can't be recovered in the field. Do not Weld on these trucks without removing or at least unhooking modules.

[BIGSTICK]

Well got the truck back and everything works great! WOOHOO!! I put about 110 miles on it last night and it was fine. I really want to thank all of you that replied with your vast knowledge of information. That is what makes these sights so great.

[Dr_Crane]

Oopsy!! I weld on my truck all the time. The rear bumper is a work bench with the welder bolted to the body. Never disconnected the batteries! My old welder was hooked to the truck battery directly! I even shorted out the 2/0 cable running to the welder which started a fire under the hood! (body and chassis grounds) Had to put it out with fire extinguisher! After that all the lights came on real dim, I though I fryed the pcm, but I turned the key and the truck started, fixed the burned wire and all is good! Guess I was lucky!

[midwest]

Dr Crane, I'm not sure if your being a smart a-- or what,but you did not weld ON your truck, you welded WITH your truck. Thats probably why you did not have an issue.A shorted cable to your welder would not be any different than an excessive current draw only affecting battery or related wiring.All I can tell you is from experience,is that I have only replaced PCM/TCM on duramaxes that were welded ON.When diagnosis reveales a PCM or BCM as failed and you look around and find welding on the truck and quiz the customer on when they had this done it is usually within a week or so.I personally have NEVER replaced a PCM/TCM on a duramax for any driveability issues.Sure it can happen but not likely.
PCM's on any newer GM vehicle are the LEAST likely component to cause a driveability issue.
I still believe the pcm was not the issue on this truck.

[Dr_Crane]

Midwest: I actually do clamp things in the vise bolted to the bumper for welding, with the welder ground clamped to the bumper. Have also welded brackets to the utility body itself.