OBD-II code U0627 indicates that a control module (often the HVAC control module or PCM) has lost communication with the refrigerant temperature sensor 'A'. This sensor monitors the temperature of the refrigerant in the A/C system, and a loss of communication can disable or impair A/C operation.
The sensor itself may have failed internally, causing it to stop sending data on the communication bus.
Open, shorted, or corroded wiring and connectors between the sensor and its control module can interrupt communication.
Loose, corroded, or backed-out terminals at the sensor connector can cause intermittent or complete loss of signal.
The module that directly communicates with the sensor may have internal faults preventing proper data exchange.
In some vehicle architectures, the PCM acts as a gateway for sensor data; a rare internal failure could cause this code, but it is the least likely cause.
Yes, the vehicle will typically remain drivable, but the air conditioning system may not work or may perform erratically.
Ignoring the code won't cause immediate engine damage, but it can lead to discomfort and potential A/C system issues if the refrigerant temperature is not properly monitored.
Almost never. The PCM is very rarely the cause of this code. The problem is usually a faulty sensor, wiring issue, or HVAC module. Replacing the PCM should only be considered after thorough diagnosis rules out all other possibilities.
A low refrigerant charge itself does not directly cause a lost communication code, but it can lead to abnormal sensor readings that may trigger other codes. The U0627 code specifically points to a communication failure, not a performance problem.