U0041: Vehicle Communication Bus B (+) High

What it means

Bus B high-side line voltage above expected range — short to power or transceiver fault. A communication loss with this module breaks any function relying on its data — diagnostic tools may show 'no response' and dependent modules can fall into limp mode.

At a glance

• Usually lights the warning light of the system that lost communication
• The engine or gearbox may go into limp mode

How it works

Bus B sends data between its connected modules over paired conductors, with the (+) conductor serving as the high-side line. U0041 means the positive line is detected above its expected voltage range, which can corrupt messages or interrupt bus communication.

Common causes

Most likely first.

1. Wire shorted to battery
2. Gateway module routing CAN messages incorrectly
3. CAN terminating resistor (120 Ω) drifted out of spec

Symptoms

• Multiple warning lights may illuminate
• Affected modules may go into limp mode or shut down
• Specific functions inoperative depending on module
• Diagnostic tools may show communication faults

How to diagnose it

1. Record all codes and freeze-frame data, then note which bus B modules report communication loss or faults at the same time.
2. Inspect bus B (+) wiring for damage, poorly repaired sections, or contact with a battery-positive feed, and check connectors for bent or bridged pins.
3. Use scan-tool network status to see which modules stop communicating and whether the fault changes when the harness is moved.
4. With the vehicle in the manufacturer's specified test state, check bus B (+) for a short to power and compare line behavior with the service information.
5. If the wiring is sound, test gateway routing, termination, and the bus transceivers of affected modules before replacing any component.

Common fixes

• Repair bus B (+) wiring shorted to a power feed.
• Correct damaged or bridged connector terminals and secure the connector.
• Replace a bus B terminating resistor only if testing finds it outside specification.
• Repair gateway routing or replace a faulty module only after circuit testing identifies it.

Can I keep driving?

Do not continue driving if the communication fault disables steering, braking, stability control, or another essential function. Otherwise, drive only as needed to reach a safe place for diagnosis, since limp mode or additional system loss may occur.