Broken or chafed wire in the D (+) data bus circuit, often at a flex point or near a connector; Corroded or loose pins in a bus connector, especially in areas exposed to moisture; Failed control module that internally shorts or opens the bus line; Damaged splice pack or junction connector where multiple bus segments meet; Aftermarket accessory improperly tapped into the bus wiring; Rodent damage to the wiring harness

DTC codes / U00xx · Network wiring and bus faults / U0057

U0057Vehicle Communication Bus D (+) Open

Q: What does code U0057 mean?

Vehicle Communication Bus D (+) Open. U0057 means the vehicle's communication bus, specifically the D (+) data line, is open or disconnected somewhere in the network. The computer that set this code tried to communicate over that bus and detected no voltage or signal on the positive data wire, so it flagged the circuit as open.

U0057 means the vehicle's communication bus, specifically the D (+) data line, is open or disconnected somewhere in the network. The computer that set this code tried to communicate over that bus and detected no voltage or signal on the positive data wire, so it flagged the circuit as open.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaNetwork wiring and bus faults

Symptoms you may notice

Multiple warning lights on the dashboard, often including the check engine light, ABS, and airbag lights
The engine may start and run, but other modules like the transmission or body control module may be unresponsive
Intermittent or complete failure of features controlled by networked modules, such as power windows, radio, or climate control
The scan tool may fail to communicate with one or more control modules
Often no symptoms besides the warning light if the open is on a non-critical branch of the bus

Common causes, most likely first

Broken or chafed wire in the D (+) data bus circuit, often at a flex point or near a connector
Corroded or loose pins in a bus connector, especially in areas exposed to moisture
Failed control module that internally shorts or opens the bus line
Damaged splice pack or junction connector where multiple bus segments meet
Aftermarket accessory improperly tapped into the bus wiring
Rodent damage to the wiring harness

How to diagnose and fix it

Connect a scan tool and check which modules can and cannot communicate to narrow down which bus segment is open
Inspect the D (+) wire at each module connector for corrosion, loose pins, or pushed-out terminals
Measure resistance and voltage on the D (+) circuit at each module to find where the signal drops out
Disconnect modules one at a time to see if the bus returns to normal, isolating a faulty module
Check splice packs and junction connectors for water intrusion or loose terminals
Repair or replace the damaged section of wire and re-test communication with all modules
Clear the code and verify the bus is stable after a test drive

What most technicians miss on a U0057

A single failed module can pull the entire D (+) bus down, so disconnecting modules one by one is often faster than chasing wires.
The D (+) line is one half of a twisted pair; an open on the D (-) line will set a different code, so confirm which wire is actually open before repairing.
Aftermarket alarms, remote starters, or dash cams tapped into the bus are a common cause that owners forget to mention.
Water intrusion in a connector far from the module that set the code can be the real fault, so inspect the whole bus path.
A U0057 can be stored by a module that is itself failing, so replacing the module that set the code without testing the bus first is a misdiagnosis trap.

Can I keep driving with U0057?

The vehicle may still start and drive, but communication failures can disable safety systems like ABS or airbags, so limit driving to a short distance to a repair shop and avoid relying on features controlled by the affected bus.

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.