[sierrap615]

if you replaced the batterys but the RKE does not work the transmitters may need reprogrammed. a special scantool is needed, any local GM dealership should be able to help you(bring in both transmitters). as a quick check before you go in, if you have a TV that uses a antenna and not cable. if the new GM transmitters are anything likey the older ones(like on my 95 buick). tune to channel 39, and press any button on the remote near the antenna and you should see the static change on the screen. if 39 doesn't work, try 40. if both 39 and 40 don't work, recheck the batterys. if one of the channels do work, the transmitters need reprogrammed or the vehicles RKE has a problem.

there are too many varibles for me to give you a solid quality answer about the fuel mileage. but check tires inflation, air filter, and repair any engine/tranmission/body problems. if the brake problem is caused by draging brakes, that will also affect fuel economy.

the brake squeak is most likey worn out pads and rotors. but it can be other things. you should have it checked by a shop soon.