I have a 2005 GTP comp G that has had intermittent problems with the cruise control and torque converter (locking and unlocking in 4th gear). I replaced the brake switch about a year ago and it did not change anything. Once in awhile my cruise wont work or it will kick out of cruise when its set BUT this has not happened in a few months. The current problem which has happened a couple times in the past (usually in the winter months) is that when running highway speeds (55-75 mph) the torque converter will unlock. When it unlocks my highway mileage will drop from my normal 28-30 mpg down to 20-22 mpg. Sometimes if I stop and shut the car off then start it back up and drive down the highway the torque converter will lock and operate normally and sometimes not. I've tried clearing the codes with my scanner while driving and it makes no difference. The P0703 (torque converter/brake switch circuit B) code is stored almost every time I scan it and maybe once every 3-6 months I will get a P0420 (catalyst system low efficiency bank 1) code but there are no other symptoms of a clogged cat. The transmission shifts fine and there is no shutter or slipping as far as I can tell and it usually runs around 170*F during the winter months.
Has anyone had this problem before? It wouldn't bother me so much if I didn't put on 600 miles almost every weekend but because I do I would like my mileage back and if its a serious problem I'd definitely like to get it fixed before it leaves me stranded...
