Sorry, I know there are numerous articles about a problem similar to this but, the breadth and shear number of posts becomes inundating and confusing as to the correct path to take. Can anyone point me to particular posts that specifically outline how to correct the following issue with a 2000 XK8 convertible (32K miles)? Thanks!
- ASC/TRAC NOT AVAILABLE
- FAILSAFE MODE
- OBDII code P0121 Throttle/Pedal Position Sensor/Switch 'A' Circuit Range/Performance
- ABS light NOT ON

 

Before you do anything else, go to autozone etc. and have the battery load tested. Your problems sound very much like weak battery. If the battery is okay, check all the connections, including grounds.

Then do a hard reset: disconnect neg batt cable and touch it to positive post for a few seconds, reconnect. Now if the codes come back return here for more ideas.