U0165
Lost Communication with Auxiliary HVAC Control Module
The Auxiliary HVAC Control Module has stopped transmitting on the vehicle data bus, so other control units no longer receive its messages. Rear or auxiliary climate control stops working. Typical causes are loss of power or ground at the module, an open or shorted CAN/LIN bus wire, a connector fault, or an internal module failure.
The Auxiliary HVAC Control Module has stopped transmitting on the vehicle data bus, so other control units no longer receive its messages. Rear or auxiliary climate control stops working. Typical causes are loss of power or ground at the module, an open or shorted CAN/LIN bus wire, a connector fault, or an internal module failure.
Common causes
- high
Auxiliary HVAC module unpowered
One of the most commonly reported causes for this code — check this first.
Typical part cost: $90-1100
- medium
CAN wiring to auxiliary HVAC broken
A plausible cause — test and verify before replacing parts.
Typical part cost: $90-1100
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First things to check
- 1Confirm the code with a scan tool and check for additional related codes.
- 2Inspect the relevant sensors, wiring, and connectors for damage or corrosion.
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Related codes
See related trouble codes
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Frequently asked questions
What does U0165 mean?
U0165 means "Lost Communication with Auxiliary HVAC Control Module". It is a generic OBD-II code that points to a fault in the network / communication.
What are the most common causes of U0165?
auxiliary hvac module unpowered; can wiring to auxiliary hvac broken; gateway module routing can messages incorrectly — these are the most commonly reported causes. Verify with a proper diagnosis before replacing parts, or use the Wrenchify app for a vehicle-specific diagnosis.
Can I keep driving with this code?
The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical. Use the Wrenchify app for a full diagnosis specific to your vehicle.
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