U016B code meaning
Lost Communication With A/C Compressor Control Module
Network system Generic code U01xx codes Check engine light
What U016B means
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.
U016B at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyWorkshop only
- Typical labor0.3 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U016B
- Air conditioning blows warm
- Check engine or service high voltage message, charging possibly limited
- Reduced battery cooling or charging power in heat
Common causes of U016B
- Most likelyCompressor unplugged while the bus was awake, stored code without real fault (GM 18-NA-096)
- PossibleCompressor low-voltage harness chafed on axle shaft or bracket (GM PIC6609)
- PossibleCompressor control module without 12 V supply or ground
- Less likelyElectric compressor inverter faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Ac compressor moduleCAN bus wiring
What each part of U016B means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 6B | The exact fault in that area. |
What to do next
- Note U016B and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U016B
What does U016B mean?
U016B means "Lost Communication With A/C Compressor Control Module". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with U016B?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will U016B fail an emissions test?
U016B is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U016B to fix?
Difficulty: workshop only. A typical repair takes 0.3 to 4 hours of work. This is a job for a workshop.
Will U016B clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.