Damaged or chafed wiring on the bus 'B' CAN high or CAN low circuits, often near a hinge, firewall pass-through, or under-seat routing; Corroded or loose connector terminals at a module on bus 'B', particularly in areas exposed to moisture; A failed or failing control module that is loading down the bus 'B' network and corrupting message traffic; Improperly installed aftermarket electronics, such as alarms or audio equipment, that tap into or interfere with the bus wiring; A shorted or open termination resistor inside one of the modules on bus 'B', which upsets the differential voltage the bus relies on; Low battery voltage or a weak charging system that causes modules to drop offline intermittently and set performance codes

DTC codes / U00xx · Network wiring and bus faults / U0075

U0075Control Module Communication Bus "B" Performance

Q: What does code U0075 mean?

Control Module Communication Bus "B" Performance. U0075 is a generic network communication code indicating that a control module has detected a performance fault on the Controller Area Network (CAN) bus designated as 'B'. The computer is not reporting a failure of any single component but rather that the bus itself is not delivering messages with the timing, integrity, or continuity expected, which can disrupt communication between multiple modules.

U0075 is a generic network communication code indicating that a control module has detected a performance fault on the Controller Area Network (CAN) bus designated as 'B'. The computer is not reporting a failure of any single component but rather that the bus itself is not delivering messages with the timing, integrity, or continuity expected, which can disrupt communication between multiple modules.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaNetwork wiring and bus faults

Symptoms you may notice

Multiple warning lights illuminated simultaneously, often including the check engine light, ABS, and traction control
Intermittent or complete failure of non-critical features such as radio, climate control, or power windows
The engine may start and run normally, or it may crank but not start if the fault affects the powertrain bus segment
Erratic gauge behavior, such as the speedometer or tachometer dropping to zero and returning
Often no symptoms besides the warning light, especially if the fault is intermittent and affects only a low-priority module
Stored communication codes in several different modules that all reference bus 'B'

Common causes, most likely first

Damaged or chafed wiring on the bus 'B' CAN high or CAN low circuits, often near a hinge, firewall pass-through, or under-seat routing
Corroded or loose connector terminals at a module on bus 'B', particularly in areas exposed to moisture
A failed or failing control module that is loading down the bus 'B' network and corrupting message traffic
Improperly installed aftermarket electronics, such as alarms or audio equipment, that tap into or interfere with the bus wiring
A shorted or open termination resistor inside one of the modules on bus 'B', which upsets the differential voltage the bus relies on
Low battery voltage or a weak charging system that causes modules to drop offline intermittently and set performance codes

How to diagnose and fix it

Verify battery state of charge and charging system output, then clear the code and test-drive to see if U0075 returns under normal voltage
Inspect the bus 'B' wiring harness for chafing, pinches, and corrosion at every connector between the modules that share that bus
Measure resistance across the CAN high and CAN low circuits at the diagnostic link connector to check for an open or shorted termination
Disconnect modules one at a time from bus 'B' and recheck bus performance to isolate a module that is pulling the network down
Use a scan tool with live network data to confirm which modules are dropping offline and correlate that with the physical bus layout
Repair or replace the damaged section of harness or the faulty connector terminals, then recheck bus voltage and message integrity
If a module is confirmed to be corrupting the bus, replace or reprogram that module and perform any required network configuration

What a bus performance code really means

A performance code on a CAN bus does not automatically mean a module has failed; it often means the bus is seeing corrupted or late messages because of a wiring or voltage problem that a simple code reader cannot pinpoint.
Technicians commonly misdiagnose U0075 as a bad module and replace parts when the real fault is a chafed wire behind a kick panel or a corroded ground that intermittently pulls the bus voltage out of range.
Aftermarket accessories wired into the CAN bus, such as dash cameras or remote starters, are a frequent and easily overlooked cause of bus performance codes because they introduce extra capacitance and noise.
Bus 'B' is often a lower-speed or body-oriented network, so the vehicle may drive normally while accessories misbehave, which leads owners to ignore the code until a more critical module drops offline.
A weak battery can set U0075 without any wiring fault at all, because modules that brown out during cranking may log bus performance errors that clear once the battery is replaced.

Can I keep driving with U0075?

The vehicle is usually safe to drive short distances to a repair shop because bus 'B' typically carries body and convenience functions rather than engine control, but avoid long trips and do not ignore the warning if multiple modules or safety systems are affected. If the engine stalls, gauges fail, or safety systems disable, stop driving and have the vehicle towed.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.