AutoDiag

U0164

Lost Communication With HVAC Control Module

Low· Fix when convenientProfessionalNetworkGeneric, all makes

What it means

A module on the vehicle network has stopped hearing from the HVAC Control Module. The HVAC Control Module controls heating and air conditioning. Lost communication is often a power, ground or wiring problem rather than a failed module.

Is it safe to drive?

Usually safe to drive, but the affected features may not work.

Symptoms

  • Several warning lights on at once
  • Heating or A/C controls not working

Probable causes

Most likely first

  1. 1Low battery voltage or poor battery connections
  2. 2Blown fuse feeding the module
  3. 3Poor ground connection
  4. 4Damaged CAN bus wiring or water in a connector
  5. 5Failed module

How to diagnose it

Work through these in order before buying parts

  1. 1Record the code and its freeze frame data (speed, load, temperature when it set), then clear it and see if it comes back.
  2. 2Check the battery and charging voltage. Low voltage is the most common cause of communication codes.
  3. 3Scan all modules: if one module is missing from the list, focus on its power, ground and connectors.
  4. 4Check the fuses that feed the module that is not communicating.
  5. 5With the battery disconnected, measure resistance between CAN High and CAN Low at the diagnostic port; about 60 Ω is normal.
  6. 6Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.

Common fixes

  • Repair battery, fuse or ground problems
  • Repair the network wiring or connector
  • Replace and program the module

This information is general guidance for all makes. Exact causes, specifications and procedures vary by vehicle, so confirm with your service manual or a qualified mechanic before replacing parts.