U0009

High Speed CAN Communication Bus (-) Shorted to Bus (+)

Car Fault Codes Network

Can you still drive? With care, short trips only

Who can fix it? Needs a workshop

Typical repair time 1 hour – 5 hours

Typical cost SAR 150 to 3,000

What it means

A module has detected that the two high-speed CAN bus wires, (+) and (-), are connected to each other. The bus carries messages as the difference between the two wires, so when they touch that difference disappears and communication usually stops across the whole bus. The code is usually stored in another module and normally comes with many lost-communication codes.

Symptoms5

Many warning lights on at once.
Scan tool cannot communicate with most or all modules.
No start, or transmission in limp mode.
Gauges such as speed, rpm and temperature stop working.
Many lost-communication codes in different modules.

Possible causes5

Insulation on both wires damaged at a chafe or pinch point, letting the copper touch.
Water or corrosion inside a connector bridging the two terminals.
A wrong earlier repair that joined the two wires.
A module with an internal fault shorting the two wires.
Harness damage after a collision or from rodents.

How to diagnose5

Read codes from the modules that respond and note how widespread the loss of communication is.
With the battery disconnected, measure resistance between the two bus wires: a healthy bus has two 120-ohm termination resistors and reads about 60 ohms; about 120 ohms points to an open or a missing resistor, and near zero points to the two wires shorted together.
Disconnect modules one at a time and measure resistance between the wires again; if the reading returns to normal after unplugging a module, the short is in that module or its branch.
Split the bus at junction points or inline connectors to isolate the shorted section.
Inspect connectors exposed to water, chafe points and any earlier repairs.

How to fix5

Dry and clean the wet connector and replace corroded terminals.
Separate the touching wires and repair their insulation, or replace the damaged harness section.
Correct any wrong earlier repair on the bus wiring.
Replace the module shorting the wires if proven faulty, then program and code it.
Clear codes in all modules and confirm communication returns and the code stays off.

Repair cost

0–500

500–2,000

2,000–5,000

5,000+

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost is low if the short is at a visible connector, rises if it is inside the harness, and is highest if it is inside a control module that needs replacing and programming.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions

How can I confirm the two wires are shorted?

With the battery disconnected, a healthy bus reads about 60 ohms between the two wires. A reading near zero confirms they are shorted together.

Why does communication stop on the whole bus?

Modules read each message from the difference between the two wires. When the wires touch, the difference disappears and no module can read the messages.

Can I drive with this code?

It is usually not advised except for a very short distance with caution if the engine runs, because many systems such as the transmission and ABS are affected.

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This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.

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