CAN Bus Performance Fault U0011
Diagnostic trouble code U0011 indicates a performance issue in the medium-speed Controller Area Network (CAN) bus. This code is set when the monitoring control module detects that signal integrity, response time, or data packet transmission falls below the manufacturer's specified performance standards, even though the bus may remain partially operational. The medium-speed CAN network typically handles communication between secondary or comfort modules, and this fault signals degraded communication quality, which can cause intermittent operation of associated systems.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Incorrect CAN bus termination or damaged termination resistors
- CAN bus wiring with excessive resistance, corrosion, or loose connections
- Short to ground or voltage on CAN High or CAN Low lines
- Electromagnetic interference (EMI) affecting bus performance
- A control module on the network causing signal degradation
- Intermittent power or ground supply to a network module
3. Symptoms You Will Notice
- Intermittent operation of comfort or secondary systems (e.g., power windows, climate control)
- Warning lights on the dashboard (e.g., check engine, system-specific warnings)
4. Step-by-Step Diagnosis
Scan for all stored codes and freeze frame data to confirm U0011 and related faults.
Visually inspect CAN bus wiring and connectors for damage, corrosion, or loose connections.
Measure resistance between CAN High and CAN Low at the OBD2 port (should be ~60 ohms with two termination resistors).
Check for shorts to power or ground on CAN lines using a multimeter.
Isolate the faulty module by disconnecting modules one at a time while monitoring bus activity.
5. Frequently Asked Questions
Is it safe to drive?▼
The vehicle may still be drivable, but intermittent failures in comfort or secondary systems can occur. It is recommended to diagnose and repair the issue promptly to avoid further complications.
How much does it cost to fix?▼
Repair costs typically range from $100 to $500, depending on whether the issue is a simple wiring repair or requires replacing a control module.