U0068: CAN Bus E High Speed Fault
Diagnostic trouble code U0068 indicates a communication failure on the Vehicle Communication Bus E (High), as defined by SAE J2012 for Controller Area Network (CAN) systems. The main control module (ECU) has detected an interruption, short circuit, or electrical anomaly on the high-speed bus designated as 'Bus E'. Loss of communication on this bus prevents proper exchange of critical data between interconnected electronic modules, potentially triggering a limited operating mode (limp mode) or disabling specific vehicle 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 to ground or voltage on the CAN E bus lines
- Open circuit in the Bus E communication wiring
- Corroded, bent, or loose connectors on control modules connected to this bus
- Internal failure of one of the electronic modules on this bus
- Incorrect termination or out-of-spec resistance in the CAN bus terminating resistors
- Severe electromagnetic interference (EMI) affecting signal integrity
3. Symptoms You Will Notice
- Check Engine Light or other warning lights illuminated
- Vehicle enters limp mode or reduced power mode
- Intermittent or complete loss of functions controlled by affected modules (e.g., transmission, ABS, stability control)
4. Step-by-Step Diagnosis
Scan all modules for related communication codes and verify which modules are offline.
Inspect the CAN E bus wiring and connectors for damage, corrosion, or loose connections.
Measure resistance across the CAN bus terminating resistors (typically 60 ohms between CAN High and CAN Low).
Check for shorts to ground or power on the CAN E bus lines using a multimeter.
Isolate the fault by disconnecting modules one at a time while monitoring bus activity.
If wiring and terminations are good, suspect a faulty module and test or replace it.
5. Frequently Asked Questions
Is it safe to drive?▼
Driving with code U0068 is not recommended as it can cause unpredictable behavior or loss of critical systems. The vehicle may enter limp mode, limiting speed and functionality. Have it diagnosed and repaired promptly.
How much does it cost to fix?▼
Repair costs vary widely depending on the cause. Simple wiring repairs may cost $100-$300, while replacing a faulty module can range from $500 to $1,500 or more, including labor and diagnostics.