I have over 200,000 miles on my 2001 Monte Carlo LS. I started to have this problem that when I drive the car and have to go over 50 miles per hour, it sticks in high gear so when I slow down the car it still races. I noticed that it only does this in the summer when I'm blowing the a/c. I took it to Auto Zone and they used their "check engine light" equipment to see what's wrong. 3 codes were given: P1887 (TCC release switch circuit fault), P0135 (HO2S 11 Heater condition (Heated Oxygen Sensor Bank 1 Sensor 1) and P0141 (HO2S 12 Heater condition - heated oxygen sensor bank 1 sensor 2). The guy from Auto Zone says that these are transmission issues. I've had several repairs done and spent thousands of dollars trying to fix the problem, but none of the repairs work. I've had a soft overhaul of the transmission, a cooler and torque converter installed, all valves updated, a solenoid kit, and the oxygen sensors replaced and the problem still exists. Is there anyone that has had this issue before and knows what to suggest for a repair?