changed tire size, now ABS INOP

[gcross]

I changed my rear tire size to a 295/50R16 (mickey thompson) on my 02 TA. (which looks sweet by the way). But now the ABS INOP, Brake and TCS off light is on. The brake feel like they are working fine. I few read this issuse is doen the different size in tires on front to back, give the ABS system a bad signal and trips it off which then trips the TCS. My question is "Is there way to tune for the bigger tires in the back and still keep the ABS working?" I did the speedo cal to fix the speedo.

[chevy052500hd]

you could try upping the tire size in the abs module, this is done with a tech 2 from gm, if it is possible on a 02 ta, I have done it on my 05 silverado. That may or may not fix the issue, I haven't tried it for that setup, I had to do it on a customers 02 silverado to get rid of the abs light for his 35" tires, I upped it to the max of 285/75/16's seemed to work in his setup.

[gcross]

thanks i'll give it a shot

[ChipsByAl]

Did the ABS INOP, Brake and TCS off lights come on before you corrected the speedometer settings with EFI_Live? F-body's with traction control have the rear ABS wheel speed sensors at the axle, not the ring gear. EFI_Live does not adjust for different tire sizes for these vehicles. The ABS/Traction Control will not work properly unless the tires are within specification.
Al

[gcross]

all three lights came on before and after the speedo cal. Understand I wont have ABS or TCS with these tire's installed. Will pulling the ABS fuse stop the lights for coming on? Im just worried about abs trying to work some times and causing a driving problem. Or should I just live with the lights?

[chevy052500hd]

when abs lights are on, system is locked out from operating. Another possiblity to elimanate the lights is cut the rear sensors and the rear inputs on the abs brain tie those inputs to the front sensors, not sure how well that will work or if it will work at all. Only isssue with that is abs system will not know if the rear tires are skidding.

[sdhager]

I changed my rear tire size to a 295/50R16 (mickey thompson) on my 02 TA. (which looks sweet by the way). But now the ABS INOP, Brake and TCS off light is on. The brake feel like they are working fine. I few read this issuse is doen the different size in tires on front to back, give the ABS system a bad signal and trips it off which then trips the TCS. My question is "Is there way to tune for the bigger tires in the back and still keep the ABS working?" I did the speedo cal to fix the speedo.

If you check the trouble codes you will probably find that you have mismatched vehicle speed between the front and rear wheel speeds in the ABS module. Since the front sensors go to the ABS module and the rear sensor goes to the PCM, the calibration must be correct for tire size in order to allow both calculations to be correct so that you have the right amount of pulses per mile. The tire size is adjustable in the ABS using the Tech 2, but you can only choose from factory options. Since you didn't change the tire size in the front, you must change the calculation that outputs the VSS signal that the ABS uses. Try looking at H104 (I think). Not sure of the location, but that is what you need to fix.

[joecar]

There are either 4 or 5 speed sensors on the vehicle:
a. 2 at front (1 at each front wheel),
b. 2 at rear (1 at each rear wheel) or just 1 on the axle ring gear;
c. 1 at the transmission output (or axle shaft on Corvette);

The ABS/EBCM (brake controller) module sees a. and b.
If the rear sensors don't agree with the front sensors, then the ABS/EBCM module will throw DTC's.

The PCM/TCM sees c.
This is what the PCM/TCM uses to lookup shift tables and also transmits it to the IPC.

EFILive can program c. via the H0101 and H0104, but you need another tool (Tech 2) to program b.