Diagnostic trouble code (DTC) U0073 stands for “Control Module Communication Bus “A” Off.” OBD code U0073 is a communication system DTC that applies to most vehicles. Usually, this code is triggered when communication is lost intermittently or fully between your vehicle’s control modules.
U0073 is a communication system diagnostic code related to your CANbus. This code can register in a variety of modules, including the PCM, TCM, anti-lock braking system (ABS), or body control module (BCM).
Your vehicle’s data network is much like a human body’s nervous system, as it connects various modules. For example, a 2019 F150 (depending on its equipment package) may have 40 modules, all of which communicate with each other. Many vehicles have far more modules than 40, and there are switches embedded in modules that send the switch signals over the network on some of them.
The U0073 code doesn’t apply to all newer vehicles. It mostly applies to vehicles equipped with the faster network referred to as the CAN bus, of which there are different speeds. CAN bus speeds are determined by the importance of the information the CAN bus is expected to deliver.
The U0073 code doesn’t apply to all newer vehicles. It mostly applies to vehicles equipped with the faster network referred to as the CAN bus, of which there are different speeds. CAN bus speeds are determined by the importance of the information the CAN bus is expected to deliver.
–Richard McCuistian, ASE Certified Master Automobile Technician
The fastest CAN busses do the most time-sensitive work on vehicles, particularly powertrain (engine/transmission) control, vehicle dynamics, etc. More recently, engine control modules (ECM) and transmission control modules (TCM) are separate modules rather than being concentrated in just one powertrain control module (PCM). Thus, some of the more important information exchanged between modules are the messages between the ECM and TCM during normal driving.
With that in mind, just about any issue a vehicle may have can be network-related, thus the bevy of Uxxx codes that can be set in modern vehicle systems.
Unexpected issues can cause network codes. For instance, a 2007 Cadillac Escalade can have a flashing traction control light and a stored network code due to extremely high fuel pressure from an in-tank pump with a bad fuel pressure regulator. With that in mind, note that Uxxx codes aren’t typically DIY serviceable beyond checking fuses, examining module connections, or looking for chafed or damaged wire harnesses. Moisture intrusion on vehicles with body water leaks can be an issue as well, and just about any module that has to be replaced must have some programming done.
Here are some of the possible causes that could trigger the U0073 code:
Common symptoms associated with the code include the following:
Resolving code U0073 can be challenging. It is usually best to leave the job to trusted professionals with the tools to isolate the concern and repair it.
However, if you’re confident about your DIY repair skills, here is a video you can watch to help you learn more about code U0073 diagnosis:
Fixing the U0073 code can be tricky, especially since solutions can vary depending on your vehicle’s make and model. With that being said, a few things you can attempt include:
Do a quick check on your vehicle’s battery to see if it’s still running strong. Low power can lead to the U0073 code being flashed.
Using a code reader, you can check for other DTC logs that might be linked to the U0073 code. Addressing the other logs might also solve U0073.
Do a quick visual inspection of the CANbus area. Any broken wires or loose connectors can trigger the U0073 code. Replacing or repairing these parts might be the simple solution you need to fixing U0073.
Keep an eye out for any TSBs from your vehicle’s manufacturer about your vehicle’s model and year. These bulletins will often let you know if there’s a specific problem linked to your vehicle’s model that needs addressing and how to get it fixed.
The CANbus module is an especially complex system that you need to be familiar with before making any type of repair. We recommend contacting a licensed mechanic for their assistance rather than attempting further repairs by yourself. Here are the steps a professional might need to do:
Similar to the U0073 code, U0077 codes are stored in the error memory of the control unit. The U0077-00 is defined as the Control Module Communication Chassis Expansion CAN Bus Off Code, which is related to communication problems of the data bus systems.
It’s typically addressed by checking the vehicle’s battery, electrical system voltage, and various system components.
Depending on your vehicle’s year, make, and model, you might have to check with your manufacturer regarding any TSBs. For example, GM issued a TSB for several Chevrolet Silverado and GMC Sierra models regarding the U0077 error code. A high resistance/open in the Communication Enable circuit 5986 can trigger various DTCs, including the U0077. Owners of said vehicles were advised to repair any opens in the circuit and review their warranty information.
Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.