There is no strategy with the ABS/TC system that defaults the transmission. Usually, in response to an ABS fault, it disables ABS because it is no longer reliable. Here is a brief description.
ANTILOCK Indicator Lamp
The ANTILOCK Indicator (ABS) is located in the instrument cluster and will illuminate if a malfunction in the ABS is detected by the electronic brake and traction control module (EBTCM). The ANTILOCK Indicator informs the driver that a condition exists which results in turning OFF the ABS function. If only the ANTILOCK Indicator is on, normal braking with full power assist is available. If the BRAKE and ANTILOCK Indicators are on, a problem may exist in the hydraulic brake system. Refer to Brake System Testing in Hydraulic Brakes. Conditions for the ANTILOCK Indicator to turn ON are as follows:
" ABS malfunction detected. As previously described, the ANTILOCK Indicator turns ON when a problem has been found in the ABS. The ANTILOCK Indicator indicates that the ABS and TCS have been disabled.
" Instrument cluster bulb check. When the ignition switch is turned to RUN, the ANTILOCK Indicator will turn on for approximately three seconds and then turn off.
" Illumination of the BRAKE warning Indicator may indicate reduced braking ability.
" Illumination of the Antilock Indicator without the BRAKE warning Indicator ON indicates only that ABS braking is no longer available. Power assisted braking without ABS control is still available.
" Refer to Brake System Testing in Hydraulic Brakes for diagnosis of any condition which causes the BRAKE warning Indicator to illuminate.
TRACTION CONTROL Indicator Lamp
" Indicator in the instrument cluster notifies driver that the EBTCM has disabled the TCS.
" Manually disabling the TCS will not activate this indicator.
" Indicator is controlled by the instrument cluster, with messages via serial data class 2 from the EBTCM.
Now obviously, I have not experienced the car, so I am just going on what I know here. In the 13 years that I have been with Cadillac, I have never seen a default to second gear as a result of brake problems. Is there a check engine light on? Try this for me. If the ABS light is on currently, with the key on, press OFF and WARMER on the climate panel. The segments of display will light up, and then codes will display by module, alphabetically. Record them codes and post them in a reply. In adiition, does it start in second gear, and stay in second gear, or is it a 1-2 type pattern starting in first?
Friday, July 16th, 2010 AT 4:09 PM