Block of codes
U00xx codes: communication bus (wiring and signals)
This block brings together the codes from U0001 to U0073 in the glossary. Open yours to see what it means, its causes and whether you can keep driving.
Reviewed by Daniel Morales, founder of Reprorace SL, on
What this block covers
Communication network
Control units talk to each other over buses such as CAN. A U code means one control unit has stopped hearing another: the cause may be that other unit, the wiring or the power supply, often a low battery.
The 72 codes of the block
- U0001High speed CAN communication bus: malfunction
- U0002High speed CAN communication bus: performance
- U0003High speed CAN communication bus (+): open circuit
- U0004High speed CAN communication bus (+): signal low
- U0005High speed CAN communication bus (+): signal high
- U0006High speed CAN communication bus (-): open circuit
- U0007High speed CAN communication bus (-): signal low
- U0008High speed CAN communication bus (-): signal high
- U0009High speed CAN communication bus (-): shorted to bus (+)
- U0010Medium speed CAN communication bus: malfunction
- U0011Medium speed CAN communication bus: performance
- U0012Medium speed CAN communication bus (+): open circuit
- U0013Medium speed CAN communication bus (+): signal low
- U0014Medium speed CAN communication bus (+): signal high
- U0015Medium speed CAN communication bus (-): open circuit
- U0016Medium speed CAN communication bus (-): signal low
- U0017Medium speed CAN communication bus (-): signal high
- U0018Medium speed CAN communication bus (-): shorted to bus (+)
- U0019Low speed CAN communication bus: malfunction
- U0020Low speed CAN communication bus: performance
- U0021Low speed CAN communication bus (+): open circuit
- U0022Low speed CAN communication bus (+): signal low
- U0023Low speed CAN communication bus (+): signal high
- U0024Low speed CAN communication bus (-): open circuit
- U0025Low speed CAN communication bus (-): signal low
- U0026Low speed CAN communication bus (-): signal high
- U0027Low speed CAN communication bus (-): shorted to bus (+)
- U0028Vehicle communication bus A: malfunction
- U0029Vehicle communication bus A: performance
- U0031Vehicle communication bus A (+): signal low
- U0032Vehicle communication bus A (+): signal high
- U0033Vehicle communication bus A (-): open circuit
- U0034Vehicle communication bus A (-): signal low
- U0035Vehicle communication bus A (-): signal high
- U0036Vehicle communication bus A: (-) line shorted to (+) line
- U0037Vehicle communication bus B: malfunction
- U0038Vehicle communication bus B: performance
- U0039Vehicle communication bus B (+): open circuit
- U0040Vehicle communication bus B (+): signal low
- U0041Vehicle communication bus B (+): signal high
- U0042Vehicle communication bus B (-): open circuit
- U0043Vehicle communication bus B (-): signal low
- U0044Vehicle communication bus B (-): signal high
- U0045Vehicle communication bus B: (-) line shorted to (+) line
- U0046Vehicle communication bus C: malfunction
- U0047Vehicle communication bus C: performance
- U0048Vehicle communication bus C (+): open circuit
- U0049Vehicle communication bus C (+): signal low
- U0050Vehicle communication bus C (+): signal high
- U0051Vehicle communication bus C (-): open circuit
- U0052Vehicle communication bus C (-): signal low
- U0053Vehicle communication bus C (-): signal high
- U0054Vehicle communication bus C: (-) line shorted to (+) line
- U0055Vehicle communication bus D: malfunction
- U0056Vehicle communication bus D: performance
- U0057Vehicle communication bus D (+): open circuit
- U0058Vehicle communication bus D (+): signal low
- U0059Vehicle communication bus D (+): signal high
- U0060Vehicle communication bus D (-): open circuit
- U0061Vehicle communication bus D (-): signal low
- U0062Vehicle communication bus D (-): signal high
- U0063Vehicle communication bus D: (-) line shorted to (+) line
- U0064Vehicle communication bus E: malfunction
- U0065Vehicle communication bus E: performance
- U0066Vehicle communication bus E (+): open circuit
- U0067Vehicle communication bus E (+): signal low
- U0068Vehicle communication bus E (+): signal high
- U0069Vehicle communication bus E (-): open circuit
- U0070Vehicle communication bus E (-): signal low
- U0071Vehicle communication bus E (-): signal high
- U0072Vehicle communication bus E: (-) line shorted to (+) line
- U0073Control module communication bus A: bus off
Other blocks
Read your car's fault codes on your phone
With an ECO-LITE in the OBD socket you see the codes in your account, with the data captured when the fault happened, and your workshop can check them remotely, always with your permission.
Keep reading
- OBD fault codes: what each one means
- Check engine light on: what to do
- How to read and clear your car's fault codes
- Will your car pass its MOT or inspection with the engine light on?
- Wi-Fi OBD2 reader: which one to choose
- Reading fault codes by car make
- Remote OBD diagnostics: what it is, how it works and what it can't do
- Vehicle diagnostics glossary