What does it mean?
P1748 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Electronic Pressure Control Solenoid Circuit Malfunction .
Symptoms
- Extremely harsh, banging shifts because the module defaults to maximum line pressure
- Or the opposite, slipping and soft shifts if pressure collapses
- MIL (check engine lamp) on with a transmission warning lamp
- Limp mode with a fixed gear and no torque converter lockup
- Harsh engagement into Drive and Reverse and rising fluid temperature
Likely causes
- Open or shorted winding inside the electronic pressure control solenoid
- Short to ground or short to battery on the solenoid drive circuit
- ATF soaked internal harness with chafed insulation against the valve body
- Corroded or leaking case connector with pushed-out pins
- Blown fuse or a lost feed to the transmission solenoid supply
- Sticking pressure regulator valve raising the current the solenoid draws
- Module driver stage failure, verified only after the solenoid and wiring pass
How to fix it
- Check battery voltage, charging output and the transmission fuses before anything else
- Read the freeze frame and note fluid temperature, gear and commanded pressure
- Measure solenoid resistance at the case connector and compare with the published value
- Test the drive circuit for opens, shorts to ground and shorts to battery with the solenoid unplugged
- Compare commanded and actual solenoid current on live data while raising engine load
- Inspect the internal harness and case connector for fluid ingress and rub-through
- Replace the pressure control solenoid, then verify line pressure with a gauge before returning the vehicle