ABS and Servic Brake System light

[randyc]

sounds like you are getting somewhere!!! keep up the good work and thanks for your efforts

[nvogel1245]

Mikel, Yes I noticed that..........................In my case no, only started after the tune.
I asked the question to see if anyone with an 07 is NOT having the problem to see if we can figure what the problem is by comparing differences. I have a theory that maybe because my truck is close to a brake job (pads are not yet squecking, but getting short), that this might be the problem.

I have a 07 avalanche ltz 4X4 with no problems.
Dont know if that helps

[randyc]

bumping to top..............don't want to be forgotten

[cbwallace]

Just bought an inTune and applied the Diablo tune and now have the same issue with ABS and Servic Brake light. No issues with this prior to applying the tune.

Chris

[cbwallace]

Some more details related to my specific situation... I have applied both the Diablo and 87 Octane tunes and the ABS and Service Brake lights come on with both after about 5 minutes of in town driving. Last night and this morning I noticed something else that caught my attention. During firm braking or moderate corner braking the the ABS would engage clearly before there was any tire slippage. This was of course within the first 5 minutes before the ABS and Brake Service lights came on! This got me to thinking that the truck must be sensing a wheel speed differential from actual vehicle speed while braking that was causing the ABS to enage. I then remembered that my truck did not have the standard 245/70-17 tires, but the optional 265/65-18's. So I went back home reapplied the tune with the appropriate tire size and now the ABS and Service Brake lights come on in about 30 seconds. I have not had an opportunity for another test drive, but will do so at lunch and see what happens.

Makes me wonder if there is something in the Speed Sensing programming related to tire size that is causing the ECM to feed data to the ABS system that depending on the tire size, causes the ABS to accumulate a tolerance variance at different rates to the point that the ABS detects too much variation and triggers the ABS to such off and the lights to come on? Perhaps my IT background is overthinking this too much, but has me thinking...

Chris

[mikel]

Some more details related to my specific situation... I have applied both the Diablo and 87 Octane tunes and the ABS and Service Brake lights come on with both after about 5 minutes of in town driving. Last night and this morning I noticed something else that caught my attention. During firm braking or moderate corner braking the the ABS would engage clearly before there was any tire slippage. This was of course within the first 5 minutes before the ABS and Brake Service lights came on! This got me to thinking that the truck must be sensing a wheel speed differential from actual vehicle speed while braking that was causing the ABS to enage. I then remembered that my truck did not have the standard 245/70-17 tires, but the optional 265/65-18's. So I went back home reapplied the tune with the appropriate tire size and now the ABS and Service Brake lights come on in about 30 seconds. I have not had an opportunity for another test drive, but will do so at lunch and see what happens.

Makes me wonder if there is something in the Speed Sensing programming related to tire size that is causing the ECM to feed data to the ABS system that depending on the tire size, causes the ABS to accumulate a tolerance variance at different rates to the point that the ABS detects too much variation and triggers the ABS to such off and the lights to come on? Perhaps my IT background is overthinking this too much, but has me thinking...

Chris

you are on the correct path, the question is, why is this issue prevalent on only 07 models...whats different about the ABS system on this truck vs an 08, 09, 2010, etc...

[randyc]

one other note with mine. I have noticed that sometimes (not everyday) BEFORE the lights come on, my brake pedal will feel like it is pushing back or kinda chatters. I let off slightly then press again and it goes away. Only happens once in awhile and only once during a drive.
I want to get a custom tune done once this issue is settled. I'm running the 87 octane setting..........................plan on upping octane and want a tune tailored to my driving and add ons (CAI and Cat Back)

[cbwallace]

Mikel, Is there any other data or information those of us having this issue can provide?

Chris

[mikel]

another customer just provided me with an ABS code that may help us diagnose this, we're still investigating.

[randyc]

mine has for the second time also put an "error code"(PO121)up.................each time I cleared them easy enough and didn't notice anything different from my truck. Don't know if this is related..........Does anyone know what that error code is?

[stroudtom]

Google is your friend...."P0121 - Throttle Position Sensor/Switch A Circuit Range/Performance Problem"

[randyc]

I did google it, probably not related.......................going to clean it this weekend

[cbwallace]

Mikel, Any progress on running down the source of the issue? I am trying to decide if I should hold off a custom tune from Lew until this is fixed or just go ahead and get it hoping the issue gets resolved at some point.

[randyc]

same boat

[06MonteSS]

Mikel, Any progress on running down the source of the issue? I am trying to decide if I should hold off a custom tune from Lew until this is fixed or just go ahead and get it hoping the issue gets resolved at some point.

no need to wait man... whatever they finally figure out, if anything, can always be updated/changed in the custom tune, no biggie....