Lost Communication with Vehicle Dynamics Control Module
The PCM lost communication with the vehicle dynamics control module.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
This code means that the engine control computer is unable to talk to the stability control system computer. When that happens, some features like traction control may not work, affecting your vehicle's handling.
What the computer is actually seeing
The main computer (PCM) expects to receive messages from the vehicle dynamics control module (VDCM) at regular intervals. If it doesn't receive a message for a certain period (usually about 1-2 seconds), it triggers this code.
What a healthy reading looks like
The VDCM should send messages over the CAN bus every 100 milliseconds. If the PCM doesn't receive these messages, it flags the U0122 code.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Check the wiring and connectors between the PCM and the VDCM for any damage or corrosion.
- 22. Inspect the battery voltage; it should be between 12.4V and 12.8V with the engine off. Recharge or replace the battery if necessary.
- 33. Use a scan tool to see if other codes are present, especially those related to the VDCM or communication.
- 44. If no wiring issues are found, disconnect the VDCM and test its power and ground pins; refer to the vehicle's service manual for pin locations and expected values.
- 55. If the VDCM isn’t powered or grounded correctly, repair wiring as needed or replace the VDCM. If no issues, recheck PCM communication. Test PCM if needed.
Common causes
- Damaged or corroded wiring in the CAN bus
- Faulty VDCM
- Bad connectors at the VDCM
- Battery voltage issues
- Faulty PCM
- Intermittent communication due to a short in the circuit
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It depends. You may lose traction control and stability features, increasing the risk of loss of control in slippery conditions.
Will this issue come back after clearing the code?
If the root cause is not fixed, the code will likely reappear.
Why is this related to other codes?
Codes like U0121 or U0123 indicate similar communication issues with the same or other modules, often sharing wiring or connector problems.
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