Diablosport Forums

Ok, so after a billion topics on the abs/brake light coming on after tunes or changing tire sizes here is the fix(this is for 2007-2010 silverados new body_

After spending days of research and hours on the phone with tech support(GM) I found the solution lol!!

Ok on gmt900's the ecms(pcm) can only be modified so much with the predator or a cutom tune, once you are out of range the EBCM(brake module) and wheels speed frequencies get out of whack causing the lights to come on. My truck is stock with 265 65 18, I could go up to 285 60 18 with no problems. I then put 295 70 18 on, used the predator to change it and baam! The lights back on, because I was just a hair out of the ecm/ebcms/vss frequency range.

I figured I would get a black bear tune(amazing by the way I removed 75% tranny tm and all of the engine tm, running an 87 tune, amazing !!!!) I had justin program my tires to the 295 70 18 and sure enough the lights come on!! I then got ahold of hypertech and inquired about the in line speedometer calibrator that plugs into the back of your cluster. It does not re program your ecm or anything, it just changes the speedo input so you are not screwing with the ecm settings and getting your frequency messed up.

So what this means is, tune away with your predator or custom pcm tune but leave your tire size STOCK, just program the hypertech unit to whatever size you are running and your speedo will be right without throwing any codes at all!! This is the ONLY solution to the abs/brake light coming on with ANY programmer when you chnage your tire sizes!!

I hope I was clear but pm me if you have any questions!!! There is nothing diablo can do or blackbear, edge or anyone. GM has locked down the calibrations and frequencies so badly that you can not go about it anyother way! So what I am saying is its not diablos fault or anyones because the lights come on, its a GM ISSUE 100%! Good luck!

This makes sense. I replaced my stock tires with larger ones. Concerned about throwing out the speedometer, I had the dealership, where I purchased the truck, flash the ecm with the new tire size. Funny thing though, the day I first got the ABS/BRAKE light warning I said "Oh s**t, did I just f**k up my truck". I immediately called Diablo support, they said the warning lights would go away after driving the truck a few times. Part of my job is driving a lot. Well after three days it never went away. I ended up restoring the factory tune. This doesn't instill much confidence in Diablo getting that kind of advice from thier support.

So what happens when you leave them stock? Does it mess with any other calibrations to how the motor runs or the speedometer reacts or anything else? The only reason I bought my predator was so I can change that kinda stuff after I lift and do 35s. Now your telling me I can't?

he is telling you that if you put 35" tires on your truck you may get a check engine light when correcting your speedometer because your change is outside of the range that the ABS module will accept. An inline device like the hypertech speedometer calibrator doesnt retune the computer, it just alters the signal before it reaches the PCM so there is no conflict with the ABS module.

This advise is for certain truck/suv customers that dont want an annoying check engine light after correcting their speedometer for larger tire sizes. The Predator was not the problem and did fix the speedometer but the check engine light was unavoidable if using the predator to do it.

So I need to get a speedometer recalibration thing to let the truck know about the tires, but don't worry about it in the predator programmer and that way my lite stays off? Am I correct?

yes you will need to get the hypertech in line speedometer re calibrator.

With ANY tuner the lights on alot of these gmt900's will come on the minute you mess with the tire size(screws with gm calibrations)

So if you have the diablo put whatever tune you want in (87, diablo etc) but leave the tire size and speedo alone.

You get the hypertech in line, program in your tire size on your pc with it and it will provide the proper cal id so the lights dont come on(it plugs right into the back of you speedo cluster) Dont worry either getting to the cluster is CAKE! It takes literally 5 minutes

i had issues with those lights too tried to get them to go away but since i got a custom tune from lew i havent seen the lights since..its been a few months ish