U0073 Control Module Communication Bus Off: Meaning, Causes, Symptoms & Fix

U0073 Control Module Communication Bus Off means a vehicle control module has detected so many communication errors on the CAN network that it has stopped transmitting. The code does not identify one failed part by itself. A damaged wire, weak power or ground, incorrect termination resistance, water intrusion, a faulty module, or an aftermarket accessory can all create the same fault.

The correct repair is therefore a network diagnosis, not an automatic control-module replacement. Start by recording all codes, checking battery voltage and fuses, and testing the CAN bus with the vehicle powered down before disconnecting modules one at a time.

What Does DTC U0073 Mean?

DTC U0073 is a generic communication code defined as Control Module Communication Bus “A” Off. Most modern vehicles use a Controller Area Network, or CAN bus, to let the engine computer, body control module, transmission controller, ABS module, instrument cluster, and other units exchange data over two twisted wires: CAN High and CAN Low.

When electrical interference or a wiring fault causes repeated invalid messages, a module’s CAN controller increases its internal error count. Once the error count reaches the bus-off threshold, that controller stops transmitting to protect the network. “Bus off” describes the network condition; it does not necessarily mean that the module which stored the code is defective.

Common Symptoms of U0073

The symptoms depend on which modules lose communication and whether the fault is constant or intermittent. A vehicle may still start and drive, or it may become completely inoperative.

• Multiple warning lamps, including ABS, airbag, traction control, or check-engine lights
• A dead, blank, or intermittently resetting instrument cluster
• No communication with one or more modules during a scan
• Hard starting, a no-start condition, reduced-power mode, or stalling
• Inoperative windows, locks, HVAC controls, radio, or lighting functions
• Transmission shift problems or a vehicle that will not shift out of Park
• Several U-codes appearing together rather than one isolated fault

An important clue is timing. If U0073 appeared immediately after a battery replacement, jump-start, collision repair, stereo installation, remote starter installation, or water leak, inspect that event first.

Most Common Causes of U0073

1. CAN wiring damage

CAN-H and CAN-L are often routed through harnesses near the battery, fuse boxes, door sills, dashboards, and engine compartments. Chafing against a bracket, a crushed harness, corrosion inside a connector, or an incorrectly repaired twisted pair can pull the network voltage out of range.

2. Poor power or ground

A control module with a loose ground, corroded power feed, blown fuse, or voltage drop may repeatedly reset and flood the network with communication errors. Check the module’s power and ground circuits under load; visual inspection alone can miss a high-resistance connection.

3. Shorted CAN High or CAN Low circuit

A short to ground, battery voltage, or between the two CAN wires can disable communication across an entire network. Even a partially shorted circuit may cause an intermittent U0073 that appears only when the harness moves, the engine vibrates, or moisture reaches a connector.

4. Incorrect or failed termination

A high-speed CAN network normally uses two 120-ohm terminating resistors. With the ignition off and the modules asleep, measuring across CAN-H and CAN-L commonly produces approximately 60 ohms because the two resistors are in parallel. A reading near 120 ohms, an open circuit, or a very low reading indicates that the network needs further testing.

5. Failed control module or aftermarket equipment

A module can internally short the CAN network, especially after water intrusion, an electrical surge, or a failed power supply. Non-factory alarm systems, trackers, remote starters, radios, and trailer interfaces are also frequent sources of improper CAN connections. Disconnecting accessories temporarily can be a useful diagnostic step.

How to Fix U0073 Control Module Communication Bus Off

Use this sequence rather than replacing parts based only on the code description.

1. Scan every available module. Record current, history, and pending codes, along with which modules communicate and which do not. A full network scan is more useful than reading only the engine computer.
2. Check the battery first. A fully charged battery should generally be near 12.6 volts with the engine off, although the exact specification varies. During cranking, excessive voltage drop can make multiple modules appear faulty.
3. Inspect fuses, grounds, and connectors. Look for green corrosion, pushed-back terminals, water tracks, damaged locks, and loose ground eyelets. Verify module power and ground with a test light or voltage-drop test, not only with an unloaded multimeter reading.
4. Measure CAN resistance correctly. Turn the ignition off, remove the key or keep the key away from the vehicle, allow the network to go to sleep, and measure resistance between CAN-H and CAN-L at the diagnostic connector. Do not measure resistance on a powered circuit. Around 60 ohms is typical for a healthy terminated high-speed CAN segment, but always confirm the vehicle’s service information.
5. Check for shorts and physical damage. Inspect the twisted-pair wiring from the diagnostic connector to the relevant junctions and modules. Do not pierce insulation unnecessarily; back-probe sealed connectors or use approved breakout leads.
6. Isolate the module that is collapsing the network. If the network resistance or communication returns when a module is disconnected, test that module’s power, ground, and connector before condemning it. Disconnect modules only with the ignition off and according to manufacturer procedures, especially airbag and high-voltage systems.
7. Repair, then verify. Use the correct wire type, splice method, twist rate, terminal, and connector seal. After repair, clear codes, perform a complete network scan, cycle the ignition, and road-test the vehicle while monitoring communication faults.

Do not install a new control module simply because it is the only unit that will not communicate. A shorted CAN wire or missing module power can produce exactly the same scan-tool result. Replacement modules may also require programming, configuration, theft relearn, or setup before the vehicle operates normally.

What Does U0073 Mean on a GMC?

On a GMC, U0073 usually points to a problem on the vehicle’s high-speed GMLAN/CAN communication network. The exact network and module list depend on the model, year, engine, and equipment. If a GMC shows U0073 together with codes such as U0100, U0101, or U0121, treat the pattern as a possible shared power, ground, or network fault rather than several unrelated failed modules.

GM vehicles can also set communication codes after low battery voltage or a disturbed connector. Check the battery terminals, underhood fuse-block connections, body grounds, and harnesses near recent repairs before pursuing expensive module programming.

What Does U0073 00 Mean on a 2014 Chevrolet Silverado?

On a 2014 Chevrolet Silverado, U0073 00 means the control module communication bus has entered an off condition; the “00” is the failure-type suffix used by the scan system and does not identify a particular replacement part. The code may be accompanied by a no-start, multiple warning messages, a dead cluster, or loss of communication with several modules.

Begin with battery condition, grounds, fuses, and a complete module scan. Then test the high-speed network at the diagnostic connector and inspect the harness around the underhood fuse block, cabin junction areas, previous collision repairs, and aftermarket equipment. Use the Silverado’s wiring diagrams and service information for the exact terminating modules and connector pinouts instead of relying on a generic pin chart.

When Is Professional Diagnosis Necessary?

Seek qualified help when the code returns immediately after clearing, several modules are offline, the vehicle has an airbag or high-voltage system, or the wiring requires connector-terminal repair. A professional shop with a factory-level scan tool, wiring diagrams, a current clamp, and an oscilloscope can observe CAN waveforms and identify intermittent faults that a basic code reader cannot.

Stop testing and arrange repair if the vehicle has burning-wire odor, melted connectors, signs of water intrusion, or unstable power supply. Continuing to drive with disabled ABS, airbag, steering, or transmission communication may create a safety risk.

Key Takeaway

U0073 is a network communication failure, not a diagnosis of one specific module. The fastest reliable path is to document all codes, stabilize battery voltage, verify power and grounds, test CAN resistance and wiring, and isolate the module or circuit that is disrupting the bus. After the repair, confirm that every module communicates and that the code does not return during a complete road test.

Frequently Asked Questions

How do I fix the U0073 code?

Scan all modules, check battery voltage, fuses, grounds, CAN wiring, connectors, and termination resistance. Repair the damaged circuit or replace the confirmed failed module, then program it if required and verify communication after clearing the code.

How do I fix control module communication bus A off?

“Bus A off” requires CAN-network diagnosis. Check for a shorted CAN-H or CAN-L wire, missing power or ground, incorrect termination, water damage, or an aftermarket device that is loading the network. Do not assume the module named by the scan tool is automatically bad.

What does U0073 mean on a GMC?

It generally means the GMC’s high-speed GMLAN/CAN network has stopped communicating normally because a module detected excessive errors. Low voltage, damaged wiring, connector corrosion, and failed modules are common causes.

What does U0073 00 mean on a 2014 Chevrolet Silverado?

It indicates a control-module communication bus-off condition, with “00” identifying the failure-type format. It does not specify which component must be replaced; the Silverado needs a complete network, power, ground, and wiring test.