CAN Bus High Line Fault
Diagnostic trouble code U0017 indicates a fault in the medium-speed Controller Area Network (CAN) bus, specifically on the CAN-High (CAN-H) signal line. According to SAE J2012, this code is set when a control module detects an interruption, short circuit, or data communication anomaly between electronic modules operating on the medium-speed CAN network (typically 125-250 kbps). The CAN-H line is one of two differential lines (CAN-High and CAN-Low) that form the communication bus; when this line fails, it disrupts or distorts information transmission between modules such as those for comfort, climate control, infotainment, or driver assistance systems.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Short circuit to ground, battery voltage, or between CAN-H and CAN-L wires
- Terminal resistance of the CAN bus out of specification (should be 120 ohms per node, total approximately 60 ohms)
- Faulty control module affecting bus impedance
- Corroded, oxidized, or damaged connector or harness splice pins
- External electromagnetic interference on the bus wiring
- Failed CAN transceiver in a master or slave control module
3. Symptoms You Will Notice
- Malfunction indicator lamp (MIL) illuminated
- Intermittent or complete loss of function in affected modules (e.g., climate control, infotainment, driver assistance)
4. Step-by-Step Diagnosis
Scan for all stored codes and freeze frame data
Visually inspect CAN bus wiring and connectors for damage, corrosion, or loose pins
Measure resistance between CAN-H and CAN-L at the OBD2 DLC (should be approximately 60 ohms)
Check for shorts to ground or battery voltage on CAN-H and CAN-L lines
Isolate modules by disconnecting them one at a time while monitoring bus resistance and communication
5. Frequently Asked Questions
Is it safe to drive?▼
The vehicle may still be drivable, but some comfort or convenience systems may not work properly. It is recommended to diagnose and repair the issue promptly to avoid further electrical problems.
How much does it cost to fix?▼
Repair costs typically range from $150 to $600, depending on the root cause (e.g., wiring repair vs. module replacement) and labor rates.