U040AInvalid Data Received From Air Conditioning Control Module
- Generic OBD-II code · Network
- How the car detects it
- J2012 separates the air conditioning control module, which governs the refrigerant side with compressor, pressures and, in electrified cars, an electric compressor drive, from the HVAC module that handles blower, flaps and set temperature (invalid data from that one is U0424). U040A is stored when frames from the A/C unit arrive but carry values the receiver cannot trust, such as a failed counter or checksum or a signal outside its range. No manufacturer documents U040A publicly. GM confirms the module itself: the 2011 Saab 9-5 code list carries U010F for lost contact with it, and GM's generic routine for U0400-U05FF reprograms the named module and replaces it only if the code returns. The compressor is likely held off, so cooling and demisting suffer; engine and emissions stay unaffected. U010F is lost contact.
- What you may notice
- Air conditioning blows warm, compressor stays off
- Windows demist slowly
- Likely causes
- PossibleSoftware of the A/C control module or of the receiver out of step
- PossibleFaulty pressure or temperature input making the module send invalid values
- PossibleDisturbed bus line, poor ground or low supply voltage at the module
- RareA/C control module internally faulty
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.