Damaged or chafed CAN bus wiring, especially at flex points or near sharp edges; Corroded or loose connectors at any module on the high-speed CAN network; A failed or improperly installed CAN bus termination resistor, usually internal to a module; A module on the bus that is internally shorted and pulling the bus voltage out of specification; Aftermarket electronics improperly tapped into the CAN wiring, causing signal interference; Water intrusion into a connector or module, leading to intermittent shorts; A faulty ground connection shared by multiple modules on the network

DTC codes / U00xx · Network wiring and bus faults / U0002

U0002High Speed CAN Communication Bus (Performance)

Q: What does code U0002 mean?

High Speed CAN Communication Bus (Performance). U0002 indicates that the high-speed Controller Area Network (CAN) communication bus is not performing as expected, meaning the modules that share data over this network are not exchanging messages reliably. The computer has detected a general performance fault on the bus itself, such as an intermittent short, excessive voltage swing, or termination issue, rather than a specific module failure.

U0002 indicates that the high-speed Controller Area Network (CAN) communication bus is not performing as expected, meaning the modules that share data over this network are not exchanging messages reliably. The computer has detected a general performance fault on the bus itself, such as an intermittent short, excessive voltage swing, or termination issue, rather than a specific module failure.

SystemNetwork

Code typeGeneric (all makes)

SeverityHigh

Fix difficultyProfessional

AreaNetwork wiring and bus faults

Symptoms you may notice

Multiple warning lights illuminated simultaneously, including the check engine light, ABS, and airbag lights
The engine may start but run poorly or stall intermittently due to lost communication between the engine and transmission modules
Inoperative accessories such as the radio, power windows, or climate control that rely on CAN bus data
A no-start condition if the bus fault prevents the engine control module from receiving critical signals
Often no symptoms besides the warning light if the fault is intermittent and the bus recovers quickly

Common causes, most likely first

Damaged or chafed CAN bus wiring, especially at flex points or near sharp edges
Corroded or loose connectors at any module on the high-speed CAN network
A failed or improperly installed CAN bus termination resistor, usually internal to a module
A module on the bus that is internally shorted and pulling the bus voltage out of specification
Aftermarket electronics improperly tapped into the CAN wiring, causing signal interference
Water intrusion into a connector or module, leading to intermittent shorts
A faulty ground connection shared by multiple modules on the network

How to diagnose and fix it

Perform a visual inspection of all accessible CAN bus wiring and connectors for damage, corrosion, or loose pins
Use a scan tool to read all modules and record which modules are communicating and which are not
Measure the CAN bus voltage with a digital multimeter at the diagnostic link connector (DLC) with the ignition on, checking for proper bias voltage
Check the resistance across the CAN bus at the DLC with the battery disconnected, looking for approximately 60 ohms
Disconnect modules one at a time to see if the bus performance improves, isolating a faulty module
Inspect and test the CAN bus termination resistors, which are often internal to the engine control module or body control module
Repair or replace any damaged wiring, connectors, or modules found during diagnosis, then clear the code and verify the repair

What most technicians miss on U0002

A common cause of U0002 that is often overlooked is an aftermarket device such as a remote starter or alarm system that has been spliced into the CAN bus wiring, disrupting signal integrity.
The code can be set by a module that is not completely dead but is intermittently pulling the bus voltage low, so disconnecting modules one at a time while monitoring bus voltage is more effective than simply replacing the first module that fails to communicate.
U0002 does not always mean the bus wiring is faulty; a weak battery or charging system issue can cause modules to drop off the bus intermittently, setting this code without any physical wiring damage.
On some vehicles, the CAN bus termination resistors are part of the instrument cluster or the engine control module, and a failure there can mimic a wiring fault, so resistance testing at the DLC is a critical first step.
Intermittent U0002 codes that appear only in cold or wet weather often point to a connector with poor pin tension or water intrusion that a static visual inspection will not reveal.

Can I keep driving with U0002?

If the warning light is on and the vehicle runs normally, you can drive it cautiously to a repair shop, but avoid long trips or high-speed driving. If the engine stalls, runs poorly, or multiple systems fail, stop driving and have the vehicle towed, as the bus fault can disable critical safety and powertrain functions without warning.

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.