Pcm Reflash

TyeeMan · June 14, 2011

Good Morning,

I have a 2002 GMC 1500HD Crew Cab, 4WD, 6.0L & 4L80E tranny.

Is it possible for me to take my truck to the dealer and have the PCM? (computer that controls the transmision) reflashed with orginal 2002 parameters?

I don't have any tune programs or anything like that. Here's why I ask, I'll try to keep it short. I've been after this problem for a while and posted on this site asking questions but am getting no where. I even went to the dealer, had the tech go out with the tech II to see if everything is ok.

Here's my issue; when I'm towing, 2K, 4K, 6K lbs, gear select in 3, my tranny pops in and out of what I think is T/C lockup, even at a steady speed going down a flat road. When she pops out of T/C lock up the tranny temp starts to rise, pushing 200 deg on a 70 degree day. The only way T/C will stay locked is if I'm running 70 MPH or over.

When I first got the truck this NEVER happened. Like clock work under lite to moderate acceleration the T/C would lock up about 55 mph and stay there until I either slowed down or I had to go to the floor for passing gear/ up a hill.

I could pull 5k lbs all day long at 150-160 trans temp.

According to the GM Tech and the Tech II the computer is telling the T/C to unlock and all is well. A - this just doesn't seem right and once again B - it never did this before and it bugs the H^^L out of me.

Is it possible for the tranny/PCM to learn different shift patterns and save them in memory?

The only reason I'm asking if the PCM can be reflashed is that if everything in the tranny is functioning normally, and the computer is telling the tranny to go into and out of T/C lock up for seemingly no reason at all, the only other thing that seems logical to me would be something changed in the PCM program somewhere along the way.

Any way, please let me know if this is possible or if I'm still barking up the wrong tree and I have to deal with this irritating shifting.

Thank you very much in advance for your response.

Still Frustrated, , , ,

Doug_Scott · June 14, 2011

I think this may actually be pretty simple. When your truck was new, it was in its best condition. The engine made the most power. Have you considered looking into the actual simple things, like plugs, wires, air filter, in other words, get a tune up. It takes torque to maintain the speed when going up hills. Have you added anything like a CAI or different exhaust? Both CAI and a higher flowing exhaust may actually reduce your low speed torque. And that low speed is like under 2000rpm. That happens to be where the engine is running at 60mph.

TyeeMan · June 15, 2011

I don't believe it's that simple. The truck is bone stock. I don't believe in cold air intakes, it's a waste of money, as well as aftermarket exhasust. The 6.0L has d@@n big pipes and a free flowing muffler, , stock. ya can't tell me after market will improve anything. The truck has 144,000 miles on it, I bought it at about 70,000. At that time every fluid was replaced, plugs were repleced and the air filter is replaced, after that every other oil change and it performed as I described for the first two or so years.

This truck is maintained better than most....

Please keep in mind that this change in tranmission operation happened from October when I towed my travel trailer home (everything was fine) and January (3 months later) when we went on a sowmobile trip.