One of the first things to do is perform an ECU code readout and a TCM code readout with a portable scan tool that supports ECU/TCM readouts to see if any fault codes are set. The tool can be purchased at most auto parts stores; also most auto parts stores will perform a readout free of charge. Post the actual codes here on the forum so that we may be able to help you further. If there is one or more fault codes set, they can help point to the malfunction. If you have a copy of the FSM for your vehicle, the code readout procedure is described there along with a listing of codes. You can download a copy of the FSM from this web site: https://ownersmanuals2.com/. The section EC.PDF is the one you need to read.