U0006

High Speed CAN Communication Bus (-) Open

Communication network (CAN bus) Generic OBD-II High

What it means

U0006 means the high-speed CAN bus low line (CAN-) is open — the "minus" wire that carries the vehicle's main data network is broken or disconnected somewhere. Because most modules share this bus, an open can knock several of them offline at once, producing multiple warning lights, loss of scan-tool communication, and often a no-start or stalling condition. It's a network wiring fault, usually a broken wire, bad connector, or failed terminating resistor, and it needs proper diagnosis rather than clearing.

High

Can I keep driving? Often not — an open high-speed CAN line can knock multiple modules off the network, causing no-start, multiple warning lights, and loss of scan-tool communication.

Common symptoms

What you'll notice

Multiple warning lights (check-engine, ABS, traction, airbag) at once
No-start or stalling, or modules dropping offline
Scan tool can't communicate with one or more modules
Gauges, displays, or accessories behaving erratically

Common causes

Most likely first

Open or broken CAN low (CAN-) wire between modulesLikely
Corroded, backed-out, or disconnected connector on the CAN- lineCommon
Faulty terminating resistor in a module or the harnessCommon
A failed module or splice dragging the bus downLess often

How to diagnose & fix

Work through it in order

Read codes from all modules; a spread of communication codes helps locate the break.
Inspect the CAN- wiring and connectors along the bus for opens, corrosion, or damage.
With the key off, measure CAN bus resistance (typically about 60 ohms across the two terminating resistors) to confirm an open.
Isolate the fault by disconnecting modules one at a time while watching the bus.
Repair the open wire, connector, or terminating resistor; replace a failed module only after the wiring is verified good.

FAQ

Quick answers

Is it safe to drive with U0006?+

Often no. Losing the CAN- line can disable safety systems and even prevent starting or running. Treat it as a get-it-diagnosed-now fault rather than driving on it.

Can I just clear U0006?+

Clearing won't reconnect an open wire — the code and the affected modules will drop off again. The break in the bus has to be repaired.

Related codes

Often seen with U0006

U0007High Speed CAN Communication Bus (-) Low U0003High Speed CAN Communication Bus (+) Open U0001High Speed CAN Communication Bus U0002High Speed CAN Communication Bus Performan

Read & clear U0006 yourself

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✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX