CAN network

U0158 — Lost Communication with HVAC Control Module

Severity: low Safe to drive

What U0158 means

One or more control modules stopped receiving messages from the HVAC (climate control) module over the CAN bus. This module normally exchanges data constantly, sending commands for the A/C compressor, blower and air doors. When those messages disappear, the system stores U0158.

Symptoms

  • Climate control panel is dead or unresponsive
  • A/C will not turn on
  • Temperature and fan speed cannot be adjusted
  • Other warning lamps may light up
  • Functions tied to the HVAC module are unavailable

Possible causes

  1. Failed HVAC control module
  2. Blown fuse for the HVAC module
  3. Open, shorted or chafed CAN bus wiring
  4. Corroded connector or terminals
  5. Missing power or ground at the HVAC module
  6. Another faulty module pulling down the bus

How to diagnose

  1. Run a full-module scan to see which modules are not communicating
  2. Check the fuses and relays that power the HVAC module
  3. Inspect the module connector and harness for corrosion, chafing or water damage
  4. Measure power supply voltage and confirm a solid ground at the module
  5. Check CAN bus resistance and voltages at the diagnostic connector
  6. If another module is suspected, disconnect modules one at a time, only following a documented procedure
  7. If power, ground and wiring are good, test or replace the HVAC module

Common fixes

  • Replace the fuse and find out why it blew
  • Repair damaged CAN wiring or connectors
  • Clean terminals and restore the ground connection
  • Replace and program the HVAC control module
  • Replace a module that is loading the bus

Questions and answers

What does U0158 mean?

It means communication with the HVAC control module has been lost. Other modules are not receiving its messages on the CAN bus, and the cause may be the module itself, its wiring or its power supply.

Can I drive with code U0158?

Usually yes, because it does not affect how the car drives. You should still fix it if you rely on defrost and heat for visibility.

Will clearing U0158 fix it?

No. The code will return until the root cause is repaired. Start by checking the fuse, power, ground and wiring of the HVAC module.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.