I am told I need a new PCM

[tRidiot]

GM LQ9 swapped into my 2004 Tahoe about 18 months ago, original PCM sent in to the builder and he told me he put a 6.0 Escalade tune on it.

Lately has been going into 'limp mode' i.e., "reduced engine power". Have to pull over, let it sit turned off a minute or two and it'll start back up and run another few minutes (sometimes) or few seconds. Had this problem 6 months ago, a local shop told me it was the throttle body and throttle body control module. They replaced both ($900) and it worked since. Now it has started again, and worse.

New shop says they have traced wiring and when plugging the computer back in, it trips the circuit for the wiring to the throttle body, even with power off. So... they say they are fairly sure it is something physical in the computer causing a short. So I need a new PCM.

Can't just buy one off Ebay, because I have the 6.0 tune, so they won't program it for a 6.0, only my stock 5.3.

I have an HP Tuners MPVI2+ with 2 credits. I purchased this 18 months or so ago, never used it. Can I just buy a PCM off Ebay (or somewhere) and download the stock Suburban 6.0 tune I see in the repository, load it onto the new PCM and plug it into my truck? Then deal with 'tuning' issues like turning on my fans and such later?

I don't really know how this works too well. I just need to try to get my truck RUNNING, then I can work on tweaking.

I have an external wiring harness I bought, as well, so I can program outside the vehicle.

[RDF1]

Read the tune off your current PCM.. Full flash into your new PCM.

[edcmat-l1]

Why don't we start with, what are the exact code numbers it's setting?

[tRidiot]

Why don't we start with, what are the exact code numbers it's setting?

I don't know this. I haven't scanned it. I'm going by what the mechanic tells me - he is pretty good, he teaches auto repair at the local Vo-Tech school, has his own shop in his off hours. I just talked to him by phone, I didn't scan it myself.

[tRidiot]

Read the tune off your current PCM.. Full flash into your new PCM.

I can do this, as well - my concern was if there is a short in the PCM, will it read properly, and am I going to need more credits to read one and program a 2nd? I'm ok with this, if I need to - but do I NEED to pull the tune off my current PCM, as it's supposedly just a generic Esky tune for a 6.0 with the electric fans turned on - which I can do at tune-time anyways, I believe. So.... do I need to 'waste' a credit for the tuner just to pull the tune?

[edcmat-l1]

I don't know this. I haven't scanned it. I'm going by what the mechanic tells me - he is pretty good, he teaches auto repair at the local Vo-Tech school, has his own shop in his off hours. I just talked to him by phone, I didn't scan it myself.

If you have your own HPtuners all you have to do is connect your scanner and check the codes yourself. You'll probably have to make it go into REP and then check them, but then at least you'd know.

It's easy enough to do. Not sure why you wouldn't want to know. If you want help diagnosing the problem that has to be the first step.

Side note, PCMs rarely go bad. Not saying it's impossible, just improbable.

[bk2life]

original PCM .

do you have a pic of the ECM?
2004 im guessing a 0411 or more likely a P59. I buy these from junk yards for $15 or $25 each.
Do like stated above, download your tune file ASAP... if it dies before you do this, than youve lost whatever tune it was.

[tRidiot]

do you have a pic of the ECM?
2004 im guessing a 0411 or more likely a P59. I buy these from junk yards for $15 or $25 each.
Do like stated above, download your tune file ASAP... if it dies before you do this, than youve lost whatever tune it was.

The tune is nothing special. It's a generic 6.0 tune - probably honestly the same as the Suburban tune in the repository. I'm not averse to it - but if it's going to 'use up' one of my keys and I have to pay $50 for another one, I have to wonder what is it benefitting me.

I will have to take my unit and go over to the shop and hook it up to read the codes. Is this also using one of my credits because it's 'registering' my PCM in order to read the codes? Or is that only if I am saving the tune currently on the PCM?

As you can see - I am new to all this.

[edcmat-l1]

The only thing you need credits for is flashing your PCM. You can scan, data log, check codes on anything you want. Anything HPtuners works as a scanner on.

In addition, you can read the calibration out of any vehicle you want, save it and view it. All without any credits. Only thing you won't be able to do is flash.

[tRidiot]

Ahhhhh ok, that is great to know. Thanks!

[2xLS1]

By taking your unit to the shop are you meaning taking just the PCM out of the vehicle? Because if you are taking just the PCM and not the whole vehicle disconnecting the power from the PCM will clear any codes set in it. I'm pretty sure I know who you are by your user name. You are in the Tulsa OK area, right? I believe I did some programming for you in OKC at my house probably around 15 years ago.

[tRidiot]

Wow! Yes, I am north of Tulsa. Good to see you! I think you did the original activation of my electric fans!

I meant I could take my HP Tuners MPVI2+ to the shop and read the computer in the truck, read the codes. The truck is at the shop across town and from the sound of things now, it won't be making it back to my house unless and until I get this problem sorted. I would have to go read the codes. I do not know if my mechanic pulled the whole PCM from the vehicle, or just disconnected it from the wiring harness to run his tests.

[2xLS1]

I could probably help with a programming a new PCM (i would recommend a cheap salvage yard PCM if you want to try replacing it) if you were in possession of the vehicle but I don't want to interfere with another shop that is already working on it. FWIW I am going to be in Tulsa a week from today.

[tRidiot]

Well I guess if I can get a cheap salvage PCM for $50 or something, it doesn't hurt to swap that out and see if it fixes my problem, if I can load a tune on it.

[2xLS1]

Any used P59 would work. (will have blue/green connectors) The one specific for a 2004 will be service # 12586242 or 12586243. They are usually $20-$40. There was a salvage yard here that would sell me about any PCM for $20 that burned to the ground earlier this year or I would get you one. They would let me go to the back and just let me dig through their pile of PCMs they had and pick out whatever I wanted.

[tRidiot]

I'll have to check into that. I'm being told on the Tahoe/Yukon forum they think it unlikely it's my PCM, it's more likely connectors or wiring, etc. This is what my mechanic has told me he was checking - so I either take his word for it - or I tow it back home and try to figure all that out myself. <sigh> I dunno. What I do know is I'm fecking tired of being without my truck.

[edcmat-l1]

Soooooo, we still don't know the exact code numbers?

[tRidiot]

Soooooo, we still don't know the exact code numbers?

No, I don't know the codes. I'm sorry, I don't have a lot of access. I'll have to dig out my HP Tuner, then drive across town and get into the truck, but have to do this when someone is at the shop, since they have the keys. I have a very demanding job and work all day every day during the week, usually work through lunch and often leave after dark, especially these days. So I have limited time to access it, and limited free time to get there.

This is why it's been sitting at the shop for... I dunno, 3+ weeks now, waiting for me to figure out what to do. I can't ask him to do anything else with it, he's already given me his opinion on what it needs - a new PCM. And sadly, my backup vehicle that I have been driving also now needs a new battery ($250+) and badly BADLY needs new rear tires ($500+) - apparently the 2 I spent $750 on 6 months and only 3k miles ago are already shot. <sigh> Things are just falling apart on me.

I've been sort of paralyzed with indecision, the money I've managed to save up and stick in the safe from my side gig (selling BBQ) is now all going to be eating up keeping my backup vehicle running - because at least it RUNS and I KNOW what is wrong with it.

Life is busy.

[SiriusC1024]

Why don't you just get a junkyard ecu and write entire your tune?

Rotate your tires. Find out what's causing the rears to wear prematurely.

Get a Walmart battery. They're like $100, reliable, warrantied. Don't pay the parts store prices.

[tRidiot]

Why don't you just get a junkyard ecu and write entire your tune?

Rotate your tires. Find out what's causing the rears to wear prematurely.

Get a Walmart battery. They're like $100, reliable, warrantied. Don't pay the parts store prices.

I'm making contact with a pulled part dealer to get a PCM - hopefully $40 plus shipping.

As for the tires, it is a sports(ish) car with asymmetric front and rear and the tires are also directional - so no rotating either front to rear OR left to right. In addition, they are also fairly evenly worn, so it's not an alignment issue per se, although it could be a camber issue. Rear tires alone run $500+ and that's buying online and cheaper tires. I DO need to get it in to get it checked, it's been a couple of years and I put some coilovers on it that probably DID change things a little bit - but no one in my town will align this thing, I've checked everywhere. My best options are an hour away, so I have to coordinate that. See again about my work schedule above.

As for the battery, I usually buy those online as well, to get the best performing battery I can due to the nature of the car AND the 4000W stereo in it. <ahem> Yeah. The current one was from June 2019 and is an Interstate AGM. I doubt I'll go back with another AGM now, but I dunno. My alt charges at 15V (custom Ohio Generator 300A), so that is good for AGM batteries - I just don't (normally) drive it enough to keep it up - of course, now it is my DD for several months this year. <sigh> With winter coming, I would really like to not have to depend on something 2.5" off the ground. <edit> I just checked WM and I am surprised at the difference in prices for batteries - of course, I'm not sure about 'Everstart', I'll need to do some research on them and see if this is a good fit for me. Even their Group 35 AGM battery is $179, which is suprising.