U0068 — Vehicle Area Network (VAN) Data Bus E (+) – Voltage High #

Note: The wording of this fault may differ depending on the vehicle manufacturer. Below is a list of known label variations:

• U0068: VAN Data Bus E (+) High Voltage (Renault, Peugeot, Citroën)
• U0068: CAN Data Bus E (+) High (Mercedes-Benz, BMW)
• U0068: Vehicle Network Bus High (Ford, GM)

Summary of code U0068 #

The U0068 diagnostic trouble code (DTC) signals a problem with the Vehicle Area Network (VAN) data bus, specifically indicating a high voltage condition on the E (+) communication line. The VAN or CAN (Controller Area Network) bus is a critical network of wires and modules that allows all computers (ECUs) in your vehicle to communicate with each other. When voltage on the E (+) line exceeds normal parameters, it can disrupt data flow between modules, potentially affecting multiple systems. This code typically means the network is either overloaded, shorted, or has a wiring fault. Ignoring this code can lead to cascading electrical and drivability issues.

Common symptoms for U0068 #

When U0068 is present, your vehicle may display a range of symptoms, from subtle glitches to more severe operational problems. The reason is that the VAN/CAN data bus is like the nervous system of your car—if the signals are scrambled, everything from safety systems to engine management may react unpredictably. Watch for:

• Intermittent or complete loss of functionality in certain modules (e.g., ABS, power steering, instrument cluster)
• Warning lights illuminated (ABS, ESP, airbag, or check engine)
• Gauge or dashboard display malfunctions
• Difficulty starting or stalling
• Communication errors during diagnostic scans
• Reduced performance of comfort features (AC, windows, infotainment)

Probable causes for U0068 (in order of frequency) #

There are several possible reasons why the VAN data bus E (+) voltage could be too high. The most common causes, listed by likelihood, include:

1. Corroded, damaged, or shorted wiring harnesses (especially where moisture can intrude)
2. Faulty or poorly grounded VAN/CAN connectors
3. Aftermarket device installation interfering with the bus (alarms, stereos, trackers)
4. Defective module (e.g., a malfunctioning ECU or control unit causing bus voltage to spike)
5. Faulty network termination resistors
6. Battery or charging system overvoltage
7. Water ingress in fuse or relay boxes

Step-by-step diagnostic for U0068 #

Diagnosing a U0068 code requires patience and a systematic approach, as network issues can be tricky. Here’s a reliable procedure:

• 1. Verify the code: Use a professional-grade scan tool to confirm U0068 and check for related codes.
• 2. Visual inspection: Examine wiring and connectors related to the VAN/CAN network for corrosion, pin damage, or loose connections, especially at module plugs and junctions.
• 3. Check voltage levels: With a multimeter, measure voltage on the E (+) line. Compare to OEM specifications (usually around 2.5V for CAN high; consult your vehicle manual for VAN specs).
• 4. Inspect for aftermarket devices: Look for recently installed electronics tapping into the network. Remove or disconnect to see if the code clears.
• 5. Isolate affected modules: Disconnect VAN/CAN modules one at a time to identify if a specific module is pulling the voltage high.
• 6. Inspect network terminations: Ensure that the correct number of resistors (typically 2 x 120 ohms for CAN) are present and within spec.
• 7. Check charging system: Verify alternator output and battery voltage for overcharging conditions.
• 8. Clear codes and retest: After each step, clear the DTC and see if it returns upon system restart.

Possible repairs for U0068 #

Repairs must address the root cause to prevent recurrence. Depending on your findings, typical fixes include:

• Repair or replace damaged/corroded wiring or connectors on the VAN/CAN network
• Improve grounding points for affected modules
• Remove or correctly rewire aftermarket devices interfering with the data bus
• Replace a faulty module (control unit) that is shorting or overdriving the network
• Replace defective network termination resistors
• Resolve charging system overvoltage (replace alternator or regulator as needed)
• Seal and clean fuse/relay boxes to prevent future water ingress

Is it safe to drive with U0068? #

Driving with a U0068 code is not recommended. While the vehicle may start and run, the high voltage condition on the data bus can cause unpredictable failures in critical safety systems (such as ABS, airbags, or power steering) at any moment. You risk losing control features or experiencing sudden module shutdowns, which can be dangerous. Address the issue as soon as possible.

Vehicles most commonly affected by U0068 #

This code is most frequently reported on European vehicles using VAN or CAN networks, as well as certain models with complex multiplexed wiring. Examples include:

• Renault (Clio, Mégane, Scenic)
• Peugeot (206, 307, 308)
• Citroën (C3, C4, C5)
• Mercedes-Benz (C-Class, E-Class)
• BMW (3 Series, 5 Series)
• Ford (Focus, Mondeo with CAN bus systems)
• General Motors (Opel/Vauxhall Astra, Zafira)

Common mistakes & best practices for U0068 #

Technicians and DIYers often make avoidable errors when tackling network codes like U0068. To save time and avoid frustration, remember:

• Don’t replace control modules before thoroughly checking wiring and connectors
• Avoid using generic scan tools that cannot access all network modules—invest in OEM-level diagnostics
• Always check for aftermarket wiring or electronics added to the vehicle
• Follow OEM wiring diagrams for accurate pinout and voltage references
• Don’t overlook simple causes like poor grounds or water-damaged connectors

Quick FAQ for code U0068 #

Still have questions? Here are quick answers to common concerns:

• Q: Does U0068 always mean a bad module?
  A: No. Most cases are caused by wiring or connector issues, not the control module itself. Replace modules only after eliminating all other possible causes.
• Q: Will clearing the code fix the problem?
  A: Clearing the code without fixing the underlying issue will only result in the DTC returning, often along with worsening symptoms. Always address the root cause.