U0002
High Speed CAN Communication Bus Performance
Network / communication (CAN bus)
Generic OBD-II
High
What it means
U0002 means the high-speed CAN data bus — the network that lets your car's control modules talk to each other — is not performing correctly. Signals are distorted or intermittent, so modules may miss messages, set unrelated codes, or drop offline. Because so many systems depend on this network, a weak bus can trigger limp mode and, in bad cases, a no-start.
High
Can I keep driving? Risky — a degraded CAN bus can make modules drop out, trigger warning lights or limp mode, and in some cases cause a no-start; have it checked before relying on the vehicle.
Common symptoms
What you'll notice
- Multiple warning lights or unrelated fault codes set at once
- Modules intermittently unresponsive (gauges, features, or scan-tool data drop out)
- Vehicle enters limp/reduced-power mode
- Hard starting or no-start in severe cases
Common causes
Most likely first
- Chafed, shorted, or broken CAN bus wiring (bus-high/bus-low pair)Likely
- Corroded or loose connector on the CAN network or a moduleCommon
- A single failing module dragging down the busCommon
- Missing or failed CAN termination resistorLess often
- Water intrusion into a connector or moduleLess often
How to diagnose & fix
Work through it in order
- Scan all modules and record every stored code — U0002 rarely acts alone, and the pattern points to the affected branch.
- Inspect CAN wiring and connectors for chafing, corrosion, and water intrusion, especially near harness junctions.
- Measure CAN bus resistance across the pair (should be about 60 ohms with two 120-ohm terminators) to check bus integrity.
- Disconnect modules one at a time to isolate a single unit pulling down the bus.
- Repair wiring or replace the faulty module, then clear codes and confirm the bus is stable.
FAQ
Quick answers
Is it safe to drive with U0002?+
Be cautious. A flaky high-speed CAN bus can make safety systems and the engine behave unpredictably, and it can cause a no-start. Get it diagnosed before depending on the car.
Can I just clear U0002?+
Clearing it may briefly quiet the dash, but if the bus fault is intermittent it will return. The underlying wiring or module problem has to be fixed.
Related codes
Often seen with U0002
Read & clear U0002 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX