What it means
An open fault has been detected on the negative line of the high-speed CAN communication bus. The affected functions depend on the vehicle network layout.
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
The high-speed CAN bus carries messages over paired CAN-High and CAN-Low wires. U0006 identifies an open in the CAN-Low line, which can disrupt communication on the affected branch and leave connected modules unreachable.
Common causes
Most likely first.
- CAN-Low wire broken
- Pin pushed back in connector
- Gateway module routing CAN messages incorrectly
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
- Scan all modules and record those that do not respond, then compare the affected modules with the vehicle’s network layout.
- Review related communication codes and event records to see whether the fault appeared after a repair, collision, or electrical disturbance.
- Inspect the CAN-Low wire and connectors for a broken conductor, pulled or backed-out pin, corrosion, or harness damage.
- Use the wiring diagram and manufacturer’s procedure to check continuity through the CAN-Low path and verify connector pin fit.
- If the CAN-Low path is intact, isolate network branches and modules as specified to locate an internal open or gateway connection fault.
Common fixes
- Reseat a loose connector or pushed-back CAN-Low terminal.
- Repair a broken or damaged CAN-Low wire in the affected branch.
- Replace a corroded or damaged connector terminal and restore the harness seal.
- Repair a confirmed internal module or gateway connection fault after checking the external wiring.
Can I keep driving?
A CAN-Low open can interrupt communication with affected modules, potentially causing warning lights, limp mode, or loss of functions. Do not drive if essential systems are affected; if the vehicle remains safe to control, keep travel short and cautious because additional functions could fail.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.