CAN network

U0184 — Lost Communication with Radio (Head Unit)

Severity: low Safe to drive

What U0184 means

U0184 means a control module, often the BCM or a gateway, stopped receiving messages from the radio head unit on the vehicle network. Normally the radio constantly exchanges data with other modules for audio, steering wheel controls, settings and sometimes cluster displays. When those messages disappear, the module logs a lost-communication code.

Symptoms

  • No audio, or the radio won't turn on
  • Steering wheel controls don't work
  • Settings menus grayed out
  • Other warning lamps may light up
  • Features tied to the radio (camera, navigation, hands-free) are unavailable

Possible causes

  1. Failed radio head unit
  2. Damaged harness or connector between the CAN bus and the radio
  3. Aftermarket stereo installed without the proper interface
  4. CAN bus wiring fault (open, short, chafed harness)
  5. Another faulty module loading down the bus
  6. Connector or terminal corrosion
  7. Power or ground fault at the radio or another module

How to diagnose

  1. Run a full-module scan to see which modules are missing from the network and whether other U-codes are stored
  2. Check whether the radio powers up, and test its fuses and constant and ignition-switched power feeds
  3. Check the ground at the radio and neighboring modules
  4. Inspect the radio connector and harness for corrosion, moisture or pushed-out terminals
  5. Measure CAN bus voltages and resistance at the diagnostic connector (about 60 ohms between CAN-H and CAN-L with power off)
  6. Find out whether an aftermarket stereo or other accessory was installed, and temporarily restore the factory setup
  7. Disconnect suspect modules one at a time, only following a documented procedure
  8. Consider whether it's a self-test history code: clear it and see if it returns

Common fixes

  • Restore power or ground to the radio, replace a blown fuse
  • Repair or replace the damaged harness, clean or replace the connector
  • Repair or replace the radio, and program it if required
  • Install the correct interface for an aftermarket stereo, or return to the factory unit
  • Replace a module that is disrupting the CAN bus

U0184 on different brands

Ford · manuals
On Ford, U0184:87 (Missing Message) is documented in SSM 51578 as a possible BCM self-test history DTC on the 2023 F-Super Duty, so it doesn't always mean the radio has actually failed.

Questions and answers

What does U0184 mean?

It means communication between the control modules and the radio was lost on the CAN network. The cause may be the radio itself, its power, the wiring or the bus.

Can I drive with U0184?

Usually yes, as it doesn't affect driving safety. But a CAN bus problem could affect other systems too, so get it checked soon.

Why do my steering wheel buttons and audio not work?

Those functions go through the radio. If it drops off the network or loses power, audio, buttons and settings stop working.

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.