U0165

Lost Communication With HVAC Control Module - Rear

Q: Is it safe to drive with U0165?

Yes — it only disables rear climate control. There's no impact on the engine, brakes, or safety systems; it's a comfort issue you can fix at your convenience.

Q: Can I just clear U0165?

It will return if the module still isn't communicating. Repair the wiring or module for it to stay clear, but there's no urgency beyond restoring rear climate control.

Communication network (climate control) Generic OBD-II Low

What it means

U0165 means the vehicle has lost communication with the rear HVAC (climate) control module — the unit that runs heating and air conditioning for the rear cabin. The only effect is that rear climate control stops working or won't respond; the engine and all safety systems are unaffected. It usually comes down to a wiring or connector fault, a power/ground problem, or a failed rear HVAC module.

Low

Can I keep driving? Fully drivable — this only affects rear climate control; the engine and safety systems are unaffected.

Real-world scan data

Seen in

123

scans in the past year

Found in

<0.1%

of scans

<0.1%

of scans that found faults

Appears alongside · share of U0165 scans

B1A28in 93.5% of scans

B1322in 90.2% of scans

U0102in 79.7% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Rear heating/air conditioning not responding or unavailable
Rear climate controls dead or erratic
Front HVAC or cluster reports the rear HVAC module missing
No temperature or fan control for rear passengers

Common causes

Most likely first

Damaged or corroded connector/wiring at the rear HVAC control moduleLikely
No power or ground to the rear HVAC module (blown fuse, bad ground)Common
Water intrusion into the module or connectorCommon
Internally failed rear HVAC control moduleLess often

How to diagnose & fix

Work through it in order

Scan all modules and confirm the rear HVAC module isn't communicating.
Check the fuse, power, and ground feeding the rear HVAC module.
Inspect the module's connector and CAN wiring for corrosion, moisture, and damage.
Repair the wiring or connector as needed.
If it still won't respond, replace the rear HVAC module, then clear and re-test.

FAQ

Quick answers

Is it safe to drive with U0165?+

Yes — it only disables rear climate control. There's no impact on the engine, brakes, or safety systems; it's a comfort issue you can fix at your convenience.

Can I just clear U0165?+

It will return if the module still isn't communicating. Repair the wiring or module for it to stay clear, but there's no urgency beyond restoring rear climate control.

Read & clear U0165 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX