U0122 — Data bus: vehicle dynamics control module – no communication #

Note: The code description may vary depending on the vehicle manufacturer.

• U0122 – Lost Communication With Vehicle Dynamics Control Module (Ford, Toyota, Honda, Subaru, Nissan, BMW, GM)
• U0122 – No Communication With VDC/ESC Module (Hyundai, Kia)
• U0122 – CAN Communication Lost With Yaw Rate Sensor (Volkswagen, Audi)

Code summary for U0122 #

The U0122 diagnostic trouble code (DTC) indicates that the vehicle’s main computer (also called the Powertrain Control Module, or PCM) has lost communication with the Vehicle Dynamics Control Module (sometimes known as the Electronic Stability Control or ESC module) via the data bus. The “data bus” refers to the vehicle’s CAN (Controller Area Network), which is the system of wires that allows the different modules to communicate. When communication fails, important stability and traction functions may be affected. This code is primarily concerned with vehicle safety systems, and may trigger warning lights on your dashboard. The loss of communication can be temporary or persistent, and may have several causes ranging from wiring issues to a failed module.

Common symptoms for DTC U0122 #

Drivers may notice a range of issues when this code is active. Sometimes, the effects are subtle, but often the vehicle will alert you with warning lights and changes in driving stability. Here are the most common symptoms:

• ABS, ESC, or traction control warning lights illuminated on the instrument panel
• Loss of traction control or stability assist functions
• Intermittent or permanent disabling of ABS or ESC systems
• Error messages such as “Check VSC,” “Stability Control Disabled,” or “ESC Off”
• Unexpected braking or handling behavior, especially in slippery conditions
• No communication with the VDC/ESC module during diagnostic scans

Probable causes of U0122 (by frequency) #

The U0122 code can be triggered by several factors. Based on field experience, here are the most likely causes, ranked from most to least common:

1. Faulty wiring or poor connections in the CAN bus circuit between the PCM and the Vehicle Dynamics Control Module
2. Loose, corroded, or damaged connectors at the control module or junction points
3. Failed Vehicle Dynamics Control Module (also known as ESC or VSC module)
4. CAN bus circuit short to ground, short to voltage, or open circuit
5. Faulty or dead battery or charging system issues causing low system voltage
6. Software errors (rare, but possible after module replacement or updates)

Step-by-step diagnostic for code U0122 #

To accurately diagnose and resolve a U0122 code, follow these steps. Proper diagnostics prevent unnecessary part replacement and ensure your vehicle’s safety systems work as intended:

• 1. Confirm the code: Use a professional scan tool to verify U0122 is active and not stored as a history code. Check for other related codes (especially U-codes).
• 2. Perform a visual inspection: Inspect all wiring and connectors related to the Vehicle Dynamics Control Module and the CAN bus. Look for signs of corrosion, loose pins, water intrusion, or damage.
• 3. Check for power and ground: With a digital multimeter, verify that the VDC/ESC module is receiving battery voltage and proper ground at its main connector.
• 4. Inspect CAN bus circuits: Using wiring diagrams, check continuity and resistance of the CAN High (CAN-H) and CAN Low (CAN-L) wires between the modules. Look for shorts or opens.
• 5. Attempt module communication: See if the scan tool can communicate directly with the VDC/ESC module. Lack of communication may indicate a faulty module or wiring fault.
• 6. Test with another module (if available): If possible, swap the suspected module with a known good one to rule out a defective part (OEM procedure required; coding may be necessary).
• 7. Check for TSBs (Technical Service Bulletins): Some vehicles have OEM bulletins for common U0122 causes or software updates.

Possible repairs for U0122 #

Once the root cause is confirmed, consider these repair actions. Always address the most likely and easiest-to-fix issues first before replacing major components.

• Repair or replace damaged wiring in the CAN bus or module harness
• Clean or tighten electrical connectors at the VDC/ESC module and related junctions
• Replace a faulty Vehicle Dynamics Control Module (may require programming or coding by OEM procedures)
• Correct battery or charging system issues (replace weak battery, fix alternator, clean terminals)
• Update or reflash module software if a TSB or OEM guidance exists

Is it safe to drive with U0122? #

Limited/No: While your vehicle may still be drivable, it is not recommended to drive with code U0122 active, especially in poor weather or on slippery roads. The loss of communication with the Vehicle Dynamics Control Module means systems like ABS (Anti-lock Braking System), traction control, and electronic stability control may not function correctly. These features are crucial for your safety, particularly during emergency maneuvers. If the warning lights are flashing or other performance issues are noticed, drive only to a qualified repair facility.

Most affected vehicles by code U0122 #

This fault is seen across a wide range of modern vehicles, but some makes and models appear more frequently in repair data:

• Ford (Edge, F-150, Fusion, Explorer)
• Subaru (Outback, Forester, Legacy, Impreza)
• Toyota (Camry, RAV4, Prius, Highlander)
• Honda (Accord, Civic, CR-V, Pilot)
• Volkswagen/Audi (Jetta, Passat, Golf, Q5)
• BMW (3 Series, 5 Series, X5)
• Hyundai/Kia (Santa Fe, Sonata, Sorento, Optima)
• GM (Chevrolet Equinox, Silverado, GMC Sierra)

Common mistakes & best practices with U0122 #

It’s easy to misdiagnose communication codes like U0122. Avoid these pitfalls, and follow industry best practices:

• Mistaking a failed module for a wiring issue (or vice versa) — always test both before replacing parts
• Ignoring other U-codes that may point to a network-wide CAN bus problem
• Disconnecting modules without proper battery disconnection, risking further electrical faults
• Skipping visual inspection — many issues are simply caused by corrosion or loose connectors
• Neglecting battery health — low voltage can disrupt module communication
• Not checking for technical bulletins that could save time and money

Quick FAQ for U0122 #

Here are fast answers to common driver and technician questions about this code:

• Q: Can I clear U0122 and keep driving?
  A: Clearing the code without fixing the underlying problem will not restore stability or traction control functions. The code and warning lights will likely return quickly.
• Q: Does replacing the module always fix U0122?
  A: No. In many cases, the problem is due to wiring, connector, or power supply issues. Only replace the module after thorough diagnosis.
• Q: Will my car fail inspection with U0122?
  A: In most states, active ABS/ESC faults will cause the vehicle to fail safety or emissions inspection.