Engine check light coming on coincidently with very rough shifting. Dealer states transmission needs replacement, even though an independent transmission shop could find no problem with the transmission. The independent mechanic maintains the problem is in the computer, which is shutting down and causing a full line pressure in the transmission, causing the rough shift. The independent shop dropped the transmission pan, inspected the fluid and visually inspected the transmission. Also kept and drove the vehicle for 2 days. Dealership insists the computer code they are receiving (P1870) indicates a transmission slip, to be remedied by a complete transmission replacement or at least an overhaul. No visual inspection of the transmission was conducted by the dealer -- only relying on a computer code to diagnose the problem. Dealer also stated they have had to replace many transmissions on this model vehicle --- "more than we care to admit." Still, an independent shop can find no internal problem and maintains it is a problem in the PCM. Dealer does not want to change PCM and will diagnose only as far as "pulling codes" from the PCM. They cannot adequately explain why the problem is intermittent and only presents intelf under certain weather conditions. When rough shifting occurs, the problem immediately goes away when the engine is shut off and re-started.

- Springfield, VA, USA