Installed my new PCM last nite

71GMC_3/4T · February 26, 2005

I swapped in my tuned PCM last night and all went fairly well, but when I tried to start it, it had the PassLock light on. I did the relearn procedure and it works.

Now, I'm wondering: did my PCM learn my truck, or did the truck learn the PCM? The reason I ask is I'm wondering if I'll have to go through this process if I ever switch back to the old PCM.

I haven't driven it much, only around the section since I had a few beers going through the relearn procedure (twice, misread directions!). She seems to have a little more pep already, and supposedly this will improve with time. I had read that everyone who had one wished they had gotten it sooner, so I bought one as soon as I could. I went for economy mainly, with tow/haul being the performance button now.

Bud · February 26, 2005

I swapped in my tuned PCM last night and all went fairly well, but when I tried to start it, it had the PassLock light on. I did the relearn procedure and it works.

Now, I'm wondering: did my PCM learn my truck, or did the truck learn the PCM? The reason I ask is I'm wondering if I'll have to go through this process if I ever switch back to the old PCM.

I haven't driven it much, only around the section since I had a few beers going through the relearn procedure (twice, misread directions!). She seems to have a little more pep already, and supposedly this will improve with time. I had read that everyone who had one wished they had gotten it sooner, so I bought one as soon as I could. I went for economy mainly, with tow/haul being the performance button now.

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Want brand did you buy?

JRKRACE · February 26, 2005

That's ironic...I Did the same exact thing last night...I swapped out my stock PCM with a PCM's For Less tune. Truck fired right up without a re-learn. Took it out, warmed it up a little, and began "observing". Now for a gas engine computer upgrade, I am quite impressed. Easy install, and it smoothed things out. The truck is more powerful and seems to feel like my wife's Yukon XL. Quite an improvment fin the 2-3000 RPM range. Motor feels unchoked. Granted it does not smoke the tires off the line but I could care less about that. It just makes the truck feel better overall. Granted this is only one day, so I'll keep you all posted. So far, this mod is definitely worth it..

dewfpo · February 26, 2005

It should feel even better after putting a couple hundred miles on it after the ECM re-learns some things. They it can really take advantage of the full 'tune'.

DEWFPO

JRKRACE · February 26, 2005

Sorry...going back to the passlock learning thing...I was told that once you do the procedure(if needed) that would be it. So your original PCM should work fine when or if you re-install it.

Butch 02 Denali · February 26, 2005

Correct! One time per PCM after it has been reflashed.

Shaners · February 27, 2005

You'll enjoy the learning process!!!

For me it took quite awhile because I don't drive the truck alot of miles, but the final result was worth it!!!

71GMC_3/4T · February 27, 2005

I got the PCM For Less from Bryan Herter.

Thanks all for the replies regarding whether or not the PCM has to be relearned at each swap.

JRKRACE, yes, that is rather ironic that both of us were probably swapping the PCM at the same time within a couple hours. Mine went real easy except I didn't note that you had to "try" to start it each time between the 11 minute cycles, so I did it all over again. I got a lot of cleanup done in the shop, checking the stop watch every so often.

I drove it around some yesterday and I think it's going to be great. Already seems to have more power, even in the normal mode. Hopefully the fuel mileage will shoot up there around twenty... Okay, maybe a mile or two per gallon to 11 or 12. I had done some rough calculations and figured that if I could get a 2 mpg increase over 100K miles, at $2 a gallon, it would save about $3300. That in itself made the PCM look like a worthwhile effort, but the performance gains were supposed to be awesome too.

No problem with knocks, pings or anything yet, nor do I expect them. I did notice the engine surged a little in reverse yesterday morning, but it only did that once and hasn't done it again.

I'm waiting for the time to come when I get to use the tow/haul button to smack down a ricer or some kid driving momma's beemer... I'm gettin' too old for this, but it's still fun if ya don't get caught!

Butch 02 Denali · February 27, 2005

You do understand that the tow/haul button can ONLY be programmed for transmission functions like shift points and shift pressure, and not any performance increase beyond what the shifting will give you?

rascal · February 28, 2005

You do understand that the tow/haul button can ONLY be programmed for transmission functions like shift points and shift pressure, and not any performance increase beyond what the shifting will give you?

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I had to re-read the thread to figure this out. :lol

since we are on the subject, am I understanding this right. you can get a tune that has 2 functions that you can toggle between? like economy and performance?

Butch 02 Denali · February 28, 2005

No you cannot. The GM PCM is not capable of it, by any tuner. Tow/haul can be set for shift points, shift pressure (firmness) and torque converter clutch lock-up, all transmission functions. There is no capability to control any engine functions.

71GMC_3/4T · February 28, 2005

No you cannot. The GM PCM is not capable of it, by any tuner. Tow/haul can be set for shift points, shift pressure (firmness) and torque converter clutch lock-up, all transmission functions. There is no capability to control any engine functions.

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Hmmmm... Bryan said he could take out the torque limit on the tow/haul side and leave it on the normal side, so that's what I asked him to do. It does run out higher and shift firmer on the tow/haul side, but I haven't tried to spin the wheels in one mode or the other yet. Maybe I misunderstood.

Butch 02 Denali · March 1, 2005

No you cannot. The GM PCM is not capable of it, by any tuner. Tow/haul can be set for shift points, shift pressure (firmness) and torque converter clutch lock-up, all transmission functions. There is no capability to control any engine functions.

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Hmmmm... Bryan said he could take out the torque limit on the tow/haul side and leave it on the normal side, so that's what I asked him to do. It does run out higher and shift firmer on the tow/haul side, but I haven't tried to spin the wheels in one mode or the other yet. Maybe I misunderstood.

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Probably! Once the abuse mode is shut off in the tune, Torque limit

does nothing for performance. It is just another abuse table. But it is already deactivated when the tuners shut of the abuse mode that makes the truck so unresponsive. Abuse mode and shift torque management are 2 completly different things!

rascal · March 3, 2005

No you cannot. The GM PCM is not capable of it, by any tuner. Tow/haul can be set for shift points, shift pressure (firmness) and torque converter clutch lock-up, all transmission functions. There is no capability to control any engine functions.

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I read that part, I meant with another button or toggle switch kinda thing? like you sig has a 91/93 tune, what does that refer too?

Butch 02 Denali · March 3, 2005

Wester's does custom dual octane tunes that can automatically adjust themselves for the octane that you put in the tank. It's like getting a custom tune with every fill-up. If I'm on a trip and can only find 91 octane, my tuning will retune the program for the 91 octane. When I get 93 again, the computer will automatically go into a short sampling mode and retune the engine to take full advantage of the 93 octane again. You don't feel anything and you don't have to do anything, it's all in the Wester's tuning!!!!