U0122 is set when the Powertrain Control Module (PCM) loses communication with the Vehicle Dynamics Control (VDC) module, which oversees stability control, traction control, and related braking functions. The code appears after a preset number of consecutive CAN messages from the VDC module are not received, indicating a problem on the controller area network (CAN) bus or within the VDC module itself. In most cases the fault lies in the VDC module, its wiring, or the CAN bus rather than the PCM.
Internal failure of the Vehicle Dynamics Control module is the most common reason it stops transmitting on the CAN bus, causing the PCM to log U0122.
Damaged, corroded, or loose wiring/connectors for power, ground, or the CAN lines can interrupt communication.
A missing or failed fuse feeding the module cuts its power, preventing it from sending CAN messages.
A compromised CAN network—such as a short between CAN‑High and CAN‑Low or an open circuit—breaks message exchange.
A malfunction in another module on the same bus (e.g., instrument cluster, body control module) can create bus errors that affect VDC communication.
The PCM may be unable to process VDC messages due to an internal fault, but this is usually considered only after all other possibilities are ruled out.
The vehicle is usually drivable, but stability control and ABS may be disabled, increasing the risk of loss of traction control; have the issue diagnosed as soon as possible.
No. The PCM sets U0122 because it cannot receive messages from the VDC module; the fault is almost always in the VDC module, its wiring, or the CAN bus, not the PCM itself.
Clearing the code without repairs will likely result in the same code returning; the underlying electrical or module issue must be addressed.
Low voltage can affect CAN bus communication, so a weak battery or faulty alternator may contribute, but the primary cause is still the VDC module or wiring issue.