U0122: Lost Communication With Vehicle Dynamics Control Module

What it means

A control module has stopped receiving expected messages from the vehicle dynamics control module. Stability or traction functions that depend on those messages may be unavailable.

At a glance

• Usually lights the warning light of the system that lost communication

How it works

The vehicle dynamics control module processes information used by stability and traction control, often coordinating braking and engine torque to help manage wheel slip and vehicle direction. Other modules expect status messages from it over the vehicle network. U0122 sets when those messages are missing, which can leave stability or traction functions unavailable.

Common causes

Most likely first.

1. Vehicle dynamics module power or ground fault
2. Damaged network wiring or connector
3. Vehicle dynamics control module failure
4. Low system voltage

Symptoms

• Stability or traction control warning
• Stability or traction functions may be unavailable
• Other communication codes

How to diagnose it

1. Scan all modules and record freeze-frame data and related ABS, stability, network, and low-voltage codes to determine whether the loss is isolated.
2. Check battery condition and charging voltage, since low system voltage can disrupt communication across several modules.
3. Inspect the vehicle dynamics module’s connectors, power and ground wiring, and network harness for looseness, corrosion, water, or physical damage.
4. Check with a scan tool whether the vehicle dynamics module responds and whether other modules also list it as offline.
5. If it is powered and grounded but does not communicate, test the network circuits to that module against the wiring diagram and manufacturer’s specification.

Common fixes

• Correct a weak battery or charging-system fault.
• Reconnect or clean a loose or corroded vehicle dynamics module connector.
• Repair damaged network wiring or connector terminals.
• Restore a faulty power or ground connection to the module.
• Replace the vehicle dynamics control module if its circuits are sound but communication remains absent.

Can I keep driving?

Drive cautiously only if braking feels normal and the route is safe; stability and traction assistance may be unavailable, especially on slippery roads or during abrupt manoeuvres. Reduce speed and avoid hard acceleration or sharp turns until the fault is resolved.