U0048: Vehicle Bus C Communication Circuit Open
The U0048 code indicates that the control module has detected an open circuit in the Vehicle Communication Bus 'C'. This means there is an electrical discontinuity in the data line (CAN High, CAN Low, or other manufacturer-defined protocol for Bus C), preventing message transmission between modules connected to that specific 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, loose, or corroded connector pins at a module on Bus C
- Defective or missing Bus C termination resistor
- Internal failure of the CAN transceiver in a module connected to Bus C
- Short to battery or ground forcing the bus into a permanent dominant/recessive state (interpreted as open due to loss of communication)
3. Symptoms You Will Notice
- Check Engine Light or other warning lights illuminated
- Communication loss with modules on Bus C, such as ABS, airbag, or instrument cluster
4. Step-by-Step Diagnosis
Use a scan tool to verify U0048 and check for related codes on other modules.
Inspect Bus C wiring and connectors for damage, corrosion, or loose connections.
Measure resistance across the CAN bus termination resistors (typically 60 ohms total).
Check for shorts to power or ground on the CAN lines.
Isolate the fault 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 loss of communication can affect critical systems like ABS or airbags. It is recommended to diagnose and repair promptly.
How much does it cost to fix?▼
Repair costs vary widely, typically ranging from $100 to $500 depending on the root cause (e.g., wiring repair vs. module replacement).