P1624 - MIL on request signal to ECM (from TCM).
The TCM has requested that the ECM turn on the MIL. (The TCM does not have the authority to turn the MIL on.)
This code informs you that an A/T related code was set and should be accompanied by another code which indicates the diagnostic condition. See Transmission Control Systems. See: Powertrain Management Transmission Control Systems
Note: Refer to TSBs for additional information.
4th gear ratio mis match
You need a trans shop to check this for you. There could be multiple issue but what concerns me is the 4th gear mis match. Comes from slipping