If you have access to it, look that DTC code up in Alldata. The description of P0742 is “TCC system stuck ON” The problem can be many things other than a defective TCC OFF switch or the TCC Pulse Width Modulating solenoid. The PCM does the actual switching of the solenoid and looks for the openning response from the TCC OFF switch. The problem could be a stuck solenoid or shorted TCC OFF switch but it also could be bad wiring; shorted wiring outside or inside the transmission; a bad PCM; or ?. The AllData troubleshooting tree goes though about 25 steps and requires a diagnostically capable scanner. Do you have access to a scanner that can pull freeze frame data; read live action data; and command transmission functions?
BTW the TCC solenoid and the TCC OFF switch are under the side cover of the transmission. To get that cover off the left half axle has to come out and a transmission mount may have to be removed. Do you feel like tackling that job? If so, go ahead and shot gun the problem by replacing both the solenoid and switch-- you might get lucky; solve the problem; and clear the code. If not, it might be better to let a someone who has the scanner and is conversant with trouble shooting the system diagnose the circuit.
Hope this helps.