1605tcm code on 99 se-l

Had my oil changed today at my buddy's shop- on the way there my ses light
came on.
Code shown is 1605tcm, his shop is mainly just shocks, tires, wheels, etc.
no heavy engine/computer work.
Can someone tell me a little bit about this code? Don't notice any symptoms
yet, the code has not come back since he read and cleared it this afternoon.

Thanks

Dave