High Speed CAN Communication Bus (+) Low
What it means
A module has detected that the (+) wire of the high-speed CAN bus is lower than expected, which usually happens when the wire touches the vehicle body or a ground circuit. Messages then become corrupted or communication between modules stops. The code is usually stored in another module, and several U codes with it confirm the problem is in the bus rather than one module.
Symptoms5
- Several warning lights on the cluster at once.
- Scan tool cannot communicate with several modules or the whole bus.
- Some gauges stop working or the transmission goes into limp mode.
- Hard starting or no start on some vehicles.
- Fault appears when certain parts are moved or in humid weather.
Possible causes5
- The (+) wire shorted to the vehicle body through insulation worn by chafing.
- Water or corrosion inside a connector linking the wire to ground.
- Wire pinched under a seat or panel or pierced by a screw after service or an accessory install.
- A module with an internal fault pulling the wire to ground.
- Harness damage after a collision or from rodents.
How to diagnose5
- Read codes from all modules and note whether communication is lost completely or only with some modules.
- Disconnect the battery and measure resistance between the (+) wire and the vehicle body; a clear path to ground means a short.
- 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 again; if the short disappears after unplugging a module, the problem is that module or its branch.
- Inspect the wiring route in areas prone to chafing and water, such as under the carpet, along body edges and at accessory installs.
How to fix5
- Dry and clean the wet connector, and fix the source of the water leak.
- Repair the damaged insulation or replace the damaged wire section, and secure it away from sharp edges.
- Free the pinched wire or the wire pierced by a screw and repair it.
- Replace the module pulling the wire to ground if proven faulty, then program and code it.
- Clear codes in all modules and confirm communication returns and the code stays off.
Repair cost
In Saudi riyals; the highlighted part is the expected range for this fault.
The cost is low if the short is at a connector or an easy-to-reach spot, rises with the time needed to trace the harness, and is highest if a control module is causing the short.
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
What is the most common cause of this code?
The wire shorting to the vehicle body through damaged insulation or water in a connector, and sometimes a wire pinched while installing an accessory.
How do I know if a control module is the cause?
Disconnect modules one at a time and measure the wire to ground again. If the short goes away after unplugging a module, that module or its branch is the cause.
Can I drive with this code?
With caution and for a short distance if the engine runs, because the transmission and ABS systems may stop working or run in limp mode.
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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