LS1TECH - Camaro and Firebird Forum Discussion

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- - Traction control problems (https://ls1tech.com/forums/pcm-diagnostics-tuning/1903804-traction-control-problems.html)

Traction control problems

Can anyone take a look at my log and explain me what is happenning. This is a stock 02 tahoe lm7 with a 60e. the only change that i made to this tune was to update the tire size from stock to 24's. using the hpt tire and gear wizard. the truck is running just fine without the tune. the speedo is off a bit and the trans shifts so so. with the tune the trans shifts a lot better. but i can only get to about 20mph and the no traction ligh will come off and the truck is left with no power or response from the throttle at all. i'll push the traction off button and everything is fine. it can be seen clearly on the log. any ideas as what's happening? with traction off it runs great. i'm triying to get this sorted out so i can start doing some tuning.I tried posting this on the HPT website, but no one seems to have an idea.
i attached the stock tune and the tire size change tune. the log is with the tire size change. i can clearly see the timing dropping out as low traction is activated.

thanks guys.

Quote:

Originally Posted by Mymonte666 (Post 19942861)

I'm far too lazy to go through all of your files, but you need to go back to stock. Make one change at a time until the truck runs right. I had a situation years ago where I made too many changes at one time, and the truck was stuck in 2nd gear "limp" mode. I made all of the same changes one at a time, and it has been running fine for years. I don't know if the problem was user error or a computer glitch, but a simple approach to fixing it eliminated trying to diagnose an unknown error.

I understand changing only one thing at the time. And that's what i did, but when you do the tire size change using the hpt wizard, it also makes changes to all your transmission tables. And thet's the thing the transmission started shifting weird when i put the tires there. Nothing major, but i could tell it was off. After doing the tire size change on hpt it shifts a lot better ie quicker, no hanging gears or shifting too early the speedo is now dead on also. One thing i noticed while comparing the filed is that almost every transmission parameter was aftected by this change, exept vss output. I was under the impression that this is the signal that is sent to the bcm for abs, speedo, traction and so on. I also tried disabling traction control on hpt and did not make a difference.
For now i have left it at that, since this issue acts like anti theft device. The truck wont go past 20 unless you turn the traction off. But i want to get this corrected so i can start doing some tuning on it and get more familiar with hpt.

HPT is only changing the tire size in the pcm, it also needs to be changed in the ABS controller with a tech 2. There is also a limit on how big you can change it.