What does code U0184 mean?

Code U0184 stands for Lost Communication with Radio.

The radio on modern vehicles can be quite complex. It doesn't just play music, it communicates with other computers throughout the vehicle. These computers are referred to as modules and there are many of them onboard, each of which is responsible for a specific part of the vehicle. For example, the engine control module is in control of the engine and the transmission control module is in charge of the transmission. Many times, the radio is referred to as the audio control module.

On most modern vehicles, the modules communicate over the Controller Area Network (CAN) bus. There are two CAN bus lines: CAN High and CAN Low. They are referred to as such because CAN High allows communication at a rate of 500k bit/second, whereas CAN Low operates at 125k bits/second. There are two terminating resistors at the ends of the CAN bus.

Code U0184 indicates the radio is not receiving or transmitting messages on the CAN bus.

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U0184 symptoms

Common causes for U0184

Code U0184 is typically caused by one of the following:

  • A dead battery
  • Radio problems
  • A problem with the CAN bus

How to diagnose and repair U0184

Perform a preliminary inspection

Sometimes U0184 can pop up intermittently, or it can result from a dead battery. This is especially true if the code is a history code and not current. Clear the code and see if it returns. If it does, the next step is to perform a visual inspection. A trained eye can check for issues such as broken wires and loose connections. If a problem is found, the issue should be repaired and the code cleared. If nothing is discovered, check for technical service bulletins (TSBs). TSBs are recommended diagnostic and repair procedures put out by the vehicle manufacturer. Finding a related TSB can greatly reduce diagnostic time.

Check the battery

Obviously, the radio needs proper battery power to operate. On some vehicles, the radio may even get "locked out" due to improper battery voltage. Check the battery and charging system. Repair or replace as needed and clear the code.

Check for other DTCs

Additional diagnostic trouble codes (DTCs) may indicate problems elsewhere that are affecting radio operation. For example, multiple communication DTCs may indicate a problem with the CAN network. Any additional DTCs should be addressed prior to diagnosing U0184.

Multiple communication DTCs may indicate a problem with the CAN bus. The bus can be checked for typically electrical defects, such as open circuits and short circuits. Bus testing usually begins with a digital multimeter or breakout box at the vehicle data link connector. Pin 6 of the connector is CAN High and pin 14 is can low. From there, further testing and repair of the CAN bus can be completed as needed.

Check for a faulty control module

Next, the radio itself should be checked. The easiest way to start this process is to attempt to communicate with the radio using a diagnostic scan tool. Once connected to the vehicle, the tool acts like just another module on the network. It can be used to address the radio directly. If the radio does not respond, there is a problem with it.

Before deeming the radio faulty, it's important to check that the radio has proper power and ground. This is usually done using a DMM. Any problems with the radio circuit should be repaired as needed and the code cleared.

Finally, before replacing the radio, its software should be checked. Sometimes, the radio can be reprogrammed rather replaced.

Other diagnostic codes related to U0184

All the 'U' codes are network communication codes. Codes U0100 to U0300 are lost communication with XX module codes.

Code U0184 technical details

This code is typically monitored when the ignition is on and battery voltage is within a specific range.

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