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U016B Lost Communication With A/C Compressor Control Module

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U016B appears when the control module of the electric A/C compressor, the inverter fed from the high-voltage battery in hybrids and EVs, stops talking to its partners. In GM's 2016 Volt table (16OBDG01) the engine controller watches frame $222 and fails after 10 s, Type B with MIL after two trips. GM bulletin 18-NA-096 (Volt and CT6 plug-in 2017-2018) explains a MIL with U016B after service: the compressor was unplugged while the bus was still awake, and a power-down followed by a battery disconnect clears it. PIC6609 (Blazer EV, Equinox EV, Optiq 2025) finds the compressor's low-voltage harness chafing against the right front driveshaft, with charging limited to 26 %. Saab lists the code as well. Cabin and battery cooling suffer.

Likely causes

Compressor unplugged while the bus was awake, stored code without real fault (GM 18-NA-096)
Compressor low-voltage harness chafed on axle shaft or bracket (GM PIC6609)
Compressor control module without 12 V supply or ground
Electric compressor inverter faulty

Symptoms

  • Air conditioning blows warm
  • Check engine or service high voltage message, charging possibly limited
  • Reduced battery cooling or charging power in heat

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€0–2,500
Time0.3–4 h

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

Parts involved

ac compressor modulecan bus wiring

Related codes

U046CU032AU010FU0164

References: gsi.ext.gm.com, static.nhtsa.gov, static.nhtsa.gov, saabwisonline.com.