Fault codes covered
55-01
The LLT thermistor provides the liquid line temperature to the PCM for use in heating control and charging. HP units have both an OCT and LLT, while AC units only have LLT. LLT is connected to the PCM through a unique 3-pin connector. If the LLT thermistor fails, full cooling and/or heating operation is permitted, however subcooling calculation in charging mode will become unavailable. A faulted LLT sensor will result in a reported LLT value of 47 F in heating mode and the OCT value in cooling mode.
The sensor is monitored continuously and if resistance is above 465kohm for 1 second this fault will occur. Once sensor value drops below 465kohm for 1 second the fault will clear. This fault does not escalate to a malfunction.
Measure resistance value of thermistor at the PCM connector. If value is above 465kohm, look for a break in the wiring or at the connector itself. If no breaks are observed, replace sensor. If measured resistance is within allowable range, replace PCM.
Source: ACHPVSR454-02SM troubleshooting pages.