NetworkU0039

Serious

Severity: Serious - have it checked soon

Vehicle communication bus B (+) open

21 brands affected · Description from Toyota data.

Key terms: Control module: a small computer that runs one part of the car

1What it means in plain English

Control modules in the car cannot communicate with each other over the vehicle network.

2Common causes

Wiring or connector fault on the communication bus
Faulty control module
Low battery voltage or poor ground
Water ingress in a connector or module
Aftermarket device interfering with the bus

3Can I drive?

Serious · drive with care

The car may run normally or may not run at all. If the module that has lost communication controls steering, brakes, park brake, charging or engine cooling, drive only if those systems feel normal; stop safely if the steering becomes heavy, a brake warning appears, or the engine temperature climbs. If the car will not start or runs badly, have it towed.

This page gives general information. It is not professional advice. For a definite diagnosis and a repair quote, ask a qualified mechanic to inspect the car.

4Brand data 21

Brand	Code	Description	System
Ashok Leyland CV	U0039	No description available	Network
BAIC Motor	U0039	Vehicle Communication Bus B (+) Open Brand	Network
BYD	U0039	Vehicle Communication Bus B (+) Open Brand	Network
Chery	U0039	Vehicle Communication Bus B (+) Open Brand	Network
Daewoo	U0039	No description available	Network
DFFS	U0039	Vehicle Communication Bus B (+) Open Brand	Network
DFFX	U0039	Vehicle Communication Bus B (+) Open Brand	Network
DFXK	U0039	Vehicle Communication Bus B (+) Open Brand	Network
EOBD	U0039	Bus truyền thông xe B (+) hở Brand	Network
Geely	U0039	Vehicle Communication Bus B (+) Open Brand	Network
GM	U0039	Vehicle Communication Bus B (+) Open Brand	Network
Great Wall	U0039	Vehicle Communication Bus B (+) Open Brand	Network
Hafei	U0039	Vehicle Communication Bus B (+) Open Brand	Network
Holden	U0039	No description available	Network
Hyundai	U0039	No description available	Network
Land Rover	U0039	Vehicle communication bus B(+) open Brand	Network
Peugeot	U0039	No description available	Network
Saab	U0039	Vehicle Communication Bus B (+) Open Brand	Network
MG (SAIC)	U0039	Vehicle Communication Bus B (+) Open Brand	Network
Tata	U0039	Vehicle Communication Bus B (+) Open Brand	Network
Toyota	U0039	Vehicle communication bus B (+) open Brand	Network

Legend: SAE is the generic J2012 description; Brand is text taken from that manufacturer’s data. Manufacturer rows keep the wording and language of the source data, and non-English text is tagged so screen readers pronounce it correctly.

5Related codes

Browse Uxxx codes or U003xx codes.