Low Pressure Sensor (PSL) Disconnection/Output Error

What does E54 mean?

The low-pressure sensor (PSL) is either disconnected or its output signal is erroneous. This prevents the system from accurately monitoring low-side refrigerant pressure, compromising operational control and safety.

• Low pressure sensor (PSL) is disconnected or not receiving power.
• PSL sensor is outputting an invalid signal or has failed internally.
• Wiring fault between the PSL sensor and the control board.

Click steps to track your progress.

1. 1

   Inspect the PSL sensor's connector on the outdoor unit PCB — verify it is securely seated.

2. 2

   Measure the output voltage or resistance of the PSL sensor according to manufacturer specifications using a multimeter.

3. 3

   Check continuity of the wiring connecting the PSL sensor to the PCB.