A short to battery voltage or ignition power on the Vehicle Communication Bus B positive wire, often from chafed insulation against a power feed; A failed control module that is internally shorted and holding the bus positive line at an elevated voltage; Corroded, pushed-back, or damaged terminals at a module connector on the affected bus, creating an intermittent high-voltage condition; Water intrusion into a connector or module housing that bridges the bus positive circuit to a power circuit; Aftermarket accessories or improper repairs that tapped into the bus wiring and introduced a voltage backfeed; A faulty voltage regulator or charging system overcharging condition that raises bus voltage above the normal operating range

DTC codes / U00xx · Network wiring and bus faults / U0080

U0080Vehicle Communication Bus B (+) High

Q: What does code U0080 mean?

Vehicle Communication Bus B (+) High. U0080 is a generic network communication code indicating that a control module detected an abnormally high voltage on the Vehicle Communication Bus B positive circuit, which is a secondary data bus used for module-to-module messaging. The computer sets this code when the bus voltage exceeds the expected upper threshold, typically because the bus is shorted to power or a module is holding the line high.

U0080 is a generic network communication code indicating that a control module detected an abnormally high voltage on the Vehicle Communication Bus B positive circuit, which is a secondary data bus used for module-to-module messaging. The computer sets this code when the bus voltage exceeds the expected upper threshold, typically because the bus is shorted to power or a module is holding the line high.

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 a communication fault message on the dashboard
Multiple warning lights on at once, such as ABS, airbag, and traction control, because several modules share the affected bus
Intermittent or complete failure of features that rely on inter-module communication, including stability control and climate control
The engine may run poorly or the transmission may shift harshly if the affected bus carries powertrain data
Often no symptoms besides the warning light, with the vehicle driving normally because the fault is isolated to a secondary bus

Common causes, most likely first

A short to battery voltage or ignition power on the Vehicle Communication Bus B positive wire, often from chafed insulation against a power feed
A failed control module that is internally shorted and holding the bus positive line at an elevated voltage
Corroded, pushed-back, or damaged terminals at a module connector on the affected bus, creating an intermittent high-voltage condition
Water intrusion into a connector or module housing that bridges the bus positive circuit to a power circuit
Aftermarket accessories or improper repairs that tapped into the bus wiring and introduced a voltage backfeed
A faulty voltage regulator or charging system overcharging condition that raises bus voltage above the normal operating range

How to diagnose and fix it

Connect a scan tool and record all stored codes across every module to confirm U0080 is active and identify which modules are offline or reporting the fault
Inspect the wiring harness for the Vehicle Communication Bus B positive circuit for chafing, pinches, or contact with power wires, especially near sharp edges and moving components
Disconnect modules one at a time from the bus and recheck bus voltage with a digital multimeter to isolate a module that is holding the line high
Measure resistance and voltage on the bus positive circuit at each module connector and compare to the manufacturer's specification to locate the short
Check for water intrusion or corrosion at connectors and module housings, and repair or replace damaged terminals and seals
Repair or replace the shorted wiring section or the faulty module, then clear codes and verify the bus voltage returns to normal with all modules communicating
Perform a road test with the scan tool connected to confirm the code does not return and all network communications are stable

What a high bus voltage really tells you

A short to power on the bus positive wire is more common than a failed module, so always inspect harness routing near the battery and fuse box before condemning any control unit
This code can be set by a single module that remains powered after the ignition is turned off and backfeeds voltage onto the bus, which is easy to miss during a key-on-only test
Aftermarket remote starters, alarms, or phone chargers plugged into the diagnostic connector can introduce voltage onto the bus and trigger U0080 without any factory defect
A weak or failing battery can cause modules to boot improperly and hold the bus line high, so load-test the battery before chasing wiring faults
U0080 often appears alongside other U-codes for the same bus, and clearing codes without fixing the short will only lead to a repeat visit

Can I keep driving with U0080?

The vehicle is usually safe to drive short distances to a repair shop because the fault typically affects a secondary communication bus, but avoid long trips and towing until diagnosed. If multiple warning lights are on or the engine runs poorly, stop driving and have the vehicle towed to prevent loss of critical module communication.

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.