U0055: CAN Bus D Communication Failure
The U0055 code indicates a communication failure on the vehicle's D bus, which is a secondary or auxiliary CAN (Controller Area Network) bus that connects various electronic control modules. This code is set when a control module detects an interruption, excessive noise, or data transmission fault on this specific communication line, preventing proper data exchange between the modules on that bus.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Damaged, cut, or shorted CAN bus wiring (to ground or battery)
- Faulty or incorrect network terminators (typically 120 ohms)
- Wet, corroded, or damaged network connectors or pins
- Electromagnetic interference (EMI) or external electrical noise
- Faulty control module generating erroneous traffic or blocking the bus
- Low battery voltage or weak charging system affecting communication
3. Symptoms You Will Notice
- Check Engine Light or other warning lights illuminated
- Intermittent or complete loss of function in modules on the D bus (e.g., infotainment, climate control, or driver assistance systems)
4. Step-by-Step Diagnosis
Scan all modules for related communication codes and note which modules are offline.
Inspect CAN bus wiring and connectors for damage, corrosion, or loose pins.
Measure resistance across the CAN bus terminals (should be ~60 ohms with two terminators).
Check battery voltage and charging system; ensure voltage is stable and within spec.
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 severity is medium. You may be able to drive, but some systems may not function properly. It's best to diagnose and repair promptly to avoid further issues.
How much does it cost to fix?▼
Costs vary widely: from $100-$200 for simple wiring repairs to $500-$1500+ for module replacement, depending on the root cause and labor rates.