I have a 05 S convertible. I am having the DSC/tire pressure light issue (no abs light). I searched the forums and found that the steering angle sensor is usually the cause. I am just curious. When I start my car the lights don't come on. They only illuminate when I release the parking brake (i always apply the parking brake when I park). Is that normal with this issue or should I be checking other things? just before this problem started I noticed the 2 lights would occasionally come on when I hit a bump but turning the car off and restarting it would shut them off. Now they are always on once I release the parking brake although every once in a blue moon they won't come on.

 

Stab in the dark... I wonder if somehow the TPM wires have been entangled with the e-brake wires and/or mechanisms. Especially when considering they initially came on with intermittent "bumps." It's been explained to me the TPM indications are a result of wheel sensor comparison.

Also, have you plugged in a code reader to your OBD II port for codes? It may help narrow down the culprit.

Like I said... stab in the dark.