Damaged or shorted wiring in the low-speed CAN bus (e.g., chafed wires, corrosion); Faulty control module on the low-speed CAN bus (e.g., body control module, door module); Poor electrical connections at module connectors or ground points; Low battery voltage or charging system issues affecting module communication; Failed termination resistor within a module on the low-speed CAN bus; Aftermarket accessories improperly wired into the CAN bus

DTC codes / U00xx · Network wiring and bus faults / U0019

U0019Low Speed CAN Communication Bus

Q: What does code U0019 mean?

Low Speed CAN Communication Bus. U0019 indicates that the low-speed Controller Area Network (CAN) communication bus, which connects various control modules in the vehicle, has failed or is experiencing communication errors. The computer detects this when modules on the low-speed CAN bus cannot reliably exchange data, often due to wiring faults, module failures, or power issues.

U0019 indicates that the low-speed Controller Area Network (CAN) communication bus, which connects various control modules in the vehicle, has failed or is experiencing communication errors. The computer detects this when modules on the low-speed CAN bus cannot reliably exchange data, often due to wiring faults, module failures, or power issues.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaNetwork wiring and bus faults

Symptoms you may notice

Illumination of the malfunction indicator lamp (MIL) or other warning lights
Multiple unrelated systems (e.g., windows, seats, climate control) may malfunction simultaneously
Intermittent or complete loss of communication with certain modules
Erratic behavior of interior accessories or body control functions
Sometimes no symptoms besides the warning light, especially if the fault is intermittent

Common causes, most likely first

Damaged or shorted wiring in the low-speed CAN bus (e.g., chafed wires, corrosion)
Faulty control module on the low-speed CAN bus (e.g., body control module, door module)
Poor electrical connections at module connectors or ground points
Low battery voltage or charging system issues affecting module communication
Failed termination resistor within a module on the low-speed CAN bus
Aftermarket accessories improperly wired into the CAN bus

How to diagnose and fix it

Perform a visual inspection of the low-speed CAN bus wiring for obvious damage, corrosion, or loose connectors
Check battery voltage and charging system operation to rule out power supply issues
Use a scan tool to retrieve all codes and identify which modules are not communicating
Measure resistance across the low-speed CAN bus (typically around 60 ohms with termination resistors) to check for open or short circuits
Disconnect modules one by one to isolate a faulty module that is pulling down the bus
Repair or replace damaged wiring or connectors as needed
Replace the faulty module if diagnosed, and clear codes to verify the repair

Low-speed CAN bus faults often misdiagnosed

A common oversight is blaming the body control module when the real issue is a corroded connector or chafed wire in a door jamb or under the dash.
Low-speed CAN is more susceptible to interference from aftermarket electronics, so check for recently installed accessories before replacing modules.
The code can be set by a module that is failing to power up correctly due to a weak battery, so always load-test the battery first.
Some vehicles use a gateway module that can set U0019 if it loses communication with the low-speed bus, even when the bus itself is fine.
Intermittent U0019 codes often stem from poor ground connections at the modules, which can be overlooked during diagnosis.

Can I keep driving with U0019?

If the vehicle runs and drives normally, you can drive it to a repair shop, but avoid relying on functions like power windows or climate control that may be affected. If multiple systems fail or the engine stalls, pull over safely 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.