Fault codes covered
52-01
The outdoor coil thermistor is used to determine when the outdoor coil is completely cleared during defrost. For this reason all defrosts performed when this fault is active will occur for the maximum time length allowed by software. 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.
*Note if any combination of OAT and OCT shorted/open are present the system will limit operation based on each individual fault.
In AC systems, this thermistor is labeled as LLT. This thermistor is used for charging and subcooling calculation. A faulted LLT will make subcooling calculation unavailable in charge mode. OCT (HP) or LLT Open (AC) connect to the PCM through a shared 5-pin connector with OAT.
Source: ACHPVSR454-02SM troubleshooting pages.