Fault Family System: Network (U-Codes) 5 SAE Codes

Invalid Data HVAC Module

Diagnostic & Technical Explanation

U040A sets when the HVAC control head or a related module reports refrigerant pressure, temperature, or actuator-position data outside a physically plausible range while communication itself stays intact. Because HVAC sensors are exposed to condensation and mounted directly on refrigerant lines subject to vibration, this pattern most often traces to a moisture-fouled pressure transducer or a temperature sensor that has slipped out of its probe well rather than a network fault.

These 5 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 5 times.

Codes in this family (5)

Code	Definition	Repair coverage
U040A	Invalid Data Received From Air Conditioning Control Module	4 ranked fixes
U0424	Invalid Data Received From HVAC Control Module	4 ranked fixes
U0425	Invalid Data Received From Auxiliary Heater Control Module	4 ranked fixes
U0466	Invalid Data Received From HVAC Control Module - Rear	4 ranked fixes
U046C	Invalid Data Received From A/C Compressor Control Module	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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