U0063 — Vehicle Area Network (VAN) Data Bus D (–) Shorted to Data Bus D (+) #

Note: The label for DTC U0063 may vary depending on the vehicle manufacturer (OEM). Below are some known variations:

• VAN Data Bus D (–) Short to Data Bus D (+) (Peugeot/Citroën)
• CAN Bus D (–) Shorted to CAN Bus D (+) (Ford)
• Vehicle Area Network Communication Bus Short (Renault)
• Communication Bus D Shorted (General Motors)

Summary of Code U0063 #

Diagnostic Trouble Code (DTC) U0063 indicates a fault in the vehicle’s communication network, specifically within the Vehicle Area Network (VAN) data bus. This bus is a communication pathway that allows electronic modules—such as the engine control module (ECM), transmission control module (TCM), and body control module (BCM)—to share information. A “short” between Data Bus D (–) and Data Bus D (+) means these two wires, meant to carry different electrical signals, are touching or electrically connected, causing communication errors. The result is that several vehicle systems may not operate correctly, triggering warning lights or abnormal behavior. Although the code often points to wiring or connector issues, module failures can also be involved. Addressing U0063 quickly is important to maintain vehicle reliability and safety.

Common Symptoms for Code U0063 #

When U0063 is present, symptoms can range from subtle warning messages to noticeable malfunctions, depending on which modules are affected by the communication breakdown. Some symptoms may seem disconnected from each other, which is often a clue that a network issue is at play. Watch for the following:

• Multiple warning lights illuminated (ABS, airbag, check engine, etc.)
• Erratic gauge readings or instrument cluster behavior
• Loss of function in certain electrical systems (windows, locks, lights)
• Communication errors when scanning with a diagnostic tool (modules not responding)
• Intermittent starting problems or failure to start
• Unexpected activation or deactivation of electronic features

Most Likely Causes for Code U0063 #

The root cause of U0063 generally lies in the wiring or connectors associated with the VAN data bus. However, faulty modules or aftermarket installations can also trigger this code. Here’s what to check, in order of probability:

1. Damaged or chafed wiring harness in the VAN bus circuit (often due to rubbing or pinching against metal parts).
2. Corroded, loose, or improperly seated connectors at modules or junction points.
3. Water ingress into junction boxes, connectors, or harnesses, causing shorts.
4. Failed electronic control module (ECU/BCM/TCM) causing internal shorts.
5. Improper installation of aftermarket electronics (alarms, radios, remote starts) tapping into the network.

Step-by-Step Diagnostic for Code U0063 #

Diagnosing U0063 requires a methodical approach, as communication faults can be elusive and intermittent. Follow this step-by-step process:

• 1. Check for other DTCs: Scan all modules for additional codes, as they may provide clues about the affected network segment.
• 2. Visual inspection of wiring: Focus on harnesses running under carpets, along door sills, or through bulkheads. Look for signs of abrasion, pinching, or rodent damage.
• 3. Inspect connectors: Disconnect and examine all connectors on the VAN data bus for corrosion, bent pins, or water intrusion.
• 4. Check for aftermarket devices: Identify any non-factory electronics connected to the data bus. Improper splicing or grounding can cause shorts.
• 5. Perform continuity and short-to-ground tests: With an ohmmeter, check for continuity between Data Bus D (–) and D (+), and verify neither is shorted to ground or power.
• 6. Isolate segments: If possible, disconnect modules one by one to see if the short clears, helping pinpoint the faulty area or component.
• 7. Reference OEM wiring diagrams: Use manufacturer schematics to trace the exact path of the bus and identify all branch points.

Possible Repairs for Code U0063 #

Once the source of the short is identified, targeted repairs will restore proper communication. Depending on your findings, these actions may be required:

• Repair or replace damaged wiring sections in the VAN data bus circuit.
• Clean, repair, or replace corroded or damaged connectors.
• Seal or reroute harnesses to prevent future water ingress or abrasion.
• Remove or correctly reinstall any aftermarket equipment interfering with the bus.
• Replace the faulty control module if internal failure is confirmed (only after all wiring checks).
• Clear codes and verify normal operation through a complete drive cycle and network scan.

Is It Safe to Drive with Code U0063? #

It is not recommended to drive with code U0063 present. While the vehicle may start and run, loss of communication between key modules can lead to unpredictable behavior—including loss of ABS, airbag, power steering, or engine management functions. In some cases, the vehicle may enter “limp mode” or fail to start altogether. Immediate diagnosis and repair are crucial to avoid safety risks and further damage.

Vehicles Most Commonly Affected by Code U0063 #

Although U0063 is a universal OBD-II code, it is most frequently reported in vehicles using the VAN data bus architecture—particularly among European brands and certain model years. The following makes and models appear more susceptible:

• Peugeot (207, 307, 308, 407, Partner)
• Citroën (C3, C4, C5, Berlingo)
• Renault (Clio, Megane, Scenic, Kangoo)
• Ford (Focus, Fiesta, Transit with VAN bus)
• Opel/Vauxhall (Zafira, Astra, Corsa)

However, the code can appear on other brands, especially where networked modules share a similar communication structure.

Common Mistakes and Best Practices for U0063 #

Troubleshooting network codes like U0063 can be challenging, and certain missteps are common even among experienced technicians. To avoid wasted time and money, keep these points in mind:

• Don’t replace control modules before thoroughly checking wiring and connectors—modules are rarely the root cause.
• Avoid clearing codes without addressing the fault; communication issues often return, compounding troubleshooting.
• Neglecting to check for aftermarket devices can lead to repeat failures.
• Always consult OEM wiring diagrams—guesswork with network circuits is risky.
• Use proper testing equipment; a basic test light is insufficient for network diagnostics.

Quick FAQ on Code U0063 #

Q: Will disconnecting the battery clear code U0063?
A: Disconnecting the battery may temporarily clear the code, but the fault will return if the underlying problem (short or wiring issue) is not fixed. Always diagnose and repair before clearing codes.

Q: Can a bad ground cause U0063?
A: Yes, a poor ground connection can cause abnormal voltages on the data bus, leading to shorts and communication errors. Always inspect ground points and repair as needed.