I have a 2008 FWD and was driving and the wrench light came on. I pulled off and the tranny was very slow engaging (slipping) when I began to accelerate. I stopped to check the ATF and looked a little low, went into the auto parts store. No Mercon V so i bought a quart of Lucas ATF fix. The wrench light went out and never came back on. Any suggestions ? BTW, 170,000 miles on it. Bought at 150,000 as a lease turn in from a local company so no info on maintenance.
Sounds like you where low on fluid, unless the dealer can pull up a maintenance record showing that it has been regularly serviced. I would advise against having trans maintenance'd, reason being transmissions that haven't properly cared for and are acting up. Changing fluid will usually result in the trans not working at all