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U046C Invalid Data Received From A/C Compressor Control Module

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U046C means that the electric A/C compressor's controller, i.e. the inverter spinning the high-voltage compressor in hybrids and EVs, sends data a receiver refuses: speed, power draw or status with bad checksums, frozen counters or values outside their range. Receivers are the climate controller and the hybrid or engine controller, which also use the refrigerant circuit to cool the traction battery. No manufacturer documents U046C publicly. GM's 2016 Volt table shows how tightly the compressor is supervised: the engine controller expects its message $222 and sets the lost-contact code U016B after 10 s as Type B (lamp on the second trip). U032A is a software mismatch, U0424 bad data from the HVAC unit. With untrusted compressor data, cabin and battery cooling may be cut back and charging or drive power limited in heat.

Likely causes

Damaged or chafed low-voltage harness or connector at the electric compressor
Compressor inverter software fault or mismatch after service
Weak 12 V supply disturbing the compressor electronics
Internal fault in the compressor control electronics

Symptoms

  • Air conditioning blows warm or switches off intermittently
  • Battery cooling limited, slower DC charging in hot weather
  • Climate or hybrid system warning in the cluster

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–2,500
Time0.5–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

ac compressor module

Related codes

U016BU032AU0424U010F

References: gsi.ext.gm.com, static.nhtsa.gov, en.wikipedia.org.