Fault Family System: Network (U-Codes) 29 SAE Codes

Lost Comm HVAC Module

Diagnostic & Technical Explanation

U010F (Lost Communication With Air Conditioning Control Module) covers loss of contact with the HVAC control head or one of the small LIN-networked blend-door, mode, and refrigerant sensor actuators behind the dash. These actuators cycle constantly with every temperature and mode change and their multi-pin connectors sit directly behind the defroster ducting, so repeated heat/cool cycling and vibration from the actuator motors themselves -- not road exposure or engine heat -- is the dominant wear mechanism. A failed actuator motor that also carries the LIN transceiver is a more common root cause here than in most other module classes, since the sensor and actuator functions share one small circuit board.

These 29 diagnostic trouble codes share one detection mechanism and one repair path, which is why MechanicDB groups them into a single authored fault family rather than repeating the same explanation 29 times.

Codes in this family (29)

Code	Definition	Repair coverage
U010F	Lost Communication With Air Conditioning Control Module	4 ranked fixes
U0164	Lost Communication With HVAC Control Module	4 ranked fixes
U0165	Lost Communication With HVAC Control Module - Rear	4 ranked fixes
U0166	Lost Communication With Auxiliary Heater Control Module	4 ranked fixes
U016B	Lost Communication With A/C Compressor Control Module	4 ranked fixes
U0605	Lost communication With A/C Refrigerant Sensor A	4 ranked fixes
U0626	Lost Communication With A/C Refrigerant Pressure Sensor 'A'	4 ranked fixes
U0627	Lost Communication With A/C Refrigerant Temperature Sensor 'A'	4 ranked fixes
U0628	Lost Communication With A/C Refrigerant Pressure Sensor 'B'	4 ranked fixes
U0629	Lost Communication With A/C Refrigerant Temperature Sensor 'B'	4 ranked fixes
U062A	Lost Communication With A/C Refrigerant Distribution Valve Actuator 'A'	4 ranked fixes
U062B	Lost Communication With A/C Refrigerant Distribution Valve Actuator 'B'	4 ranked fixes
U062C	Lost Communication With A/C Refrigerant Distribution Valve Actuator 'C'	4 ranked fixes
U062D	Lost Communication With A/C Refrigerant Distribution Valve Actuator 'D'	4 ranked fixes
U062E	Lost Communication With A/C Refrigerant Expansion Valve Actuator	4 ranked fixes
U0658	Lost Communication With Windshield Temperature Sensor	4 ranked fixes
U0659	Lost Communication With Left Front Temperature Actuator	4 ranked fixes
U065A	Lost Communication With Right Front Temperature Actuator	4 ranked fixes
U065B	Lost Communication With Left Front Mode Actuator	4 ranked fixes
U065C	Lost Communication With Right Front Mode Actuator	4 ranked fixes
U065D	Lost Communication With Air Intake Actuator	4 ranked fixes
U065E	Lost Communication With Ram Air Actuator	4 ranked fixes
U065F	Lost Communication With Left Rear Temperature Actuator A	4 ranked fixes
U0660	Lost Communication With Left Rear Temperature Actuator B	4 ranked fixes
U0661	Lost Communication With Right Rear Temperature Actuator A	4 ranked fixes
U0662	Lost Communication With Right Rear Temperature Actuator B	4 ranked fixes
U0663	Lost Communication With Rear Mode Actuator	4 ranked fixes
U0664	Lost Communication With Rear HVAC Air Cutoff Actuator	4 ranked fixes
U0693	Lost Communication With Humidity Sensor	4 ranked fixes

What this page does not show

This page publishes the fault mechanism and the code index. The licensed dataset adds, for every one of the 15,886 codes, the full authored repair set (56,729 procedures in total) with the fields deliberately withheld here:

Procedures 2..n after the first-listed procedure
Aftermarket parts cost ranges in USD (est_parts_cost_min/max_usd)
Professional labor-hour estimates (est_labor_hours)
Step-by-step diagnostic and repair instructions
Replacement-part mappings and catalog lookups
6,637 manufacturer-specific OEM codes across 32 makes ($149 tier)

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