Ok I took a look in dealer connect. The
trans control relay sends 12v to the various slonoids. If it's only missing voltage to the 3/4 shift solenoid 12v supply is not the issue. The 3/4 solenoid is controlled by the PCM grounding circuit T60 (brown wire) at connector C2 cavity 21. Either the 3/4 solenoid, open in circuit T60 or a faulty PCM. To test disconnect PCM connector C2 test lamp connected to ground and pin 21. Touch a wire connected to ground to cavity 30 (pink wire). If the solenoid and circuit are good the test lamp wil illuminate.
Doug