What this code means
U0122 may indicate that the body control module has lost communication with the VSA and ABS side of the vehicle network.
What the vehicle may do
- The vehicle may show ABS or stability-control related warnings.
- The concern can appear as a network communication fault rather than a direct mechanical failure.
- The symptom may depend on whether the VSA modulator-control unit starts and communicates normally.
Possible fault areas
- A possible VSA modulator-control unit startup issue.
- A possible power or ground circuit problem at the VSA modulator-control unit.
- A possible F-CAN communication path concern through the network or gateway side.
- A possible connection or module communication concern affecting the body control module receiving the expected data.
Diagnostic path
Code overview
On this 2016 to 2024 Honda Civic with the 1.5 turbo engine, U0122 is a network communication code. In plain terms, the body control module may not be receiving the VSA and ABS information it expects. The vehicle may show stability-control or ABS-related warnings, and the fault area can be in the VSA modulator-control unit startup, its power and ground supply, or the F-CAN communication path through the network. Treat it like a communication diagnosis, not a parts call.
Start with the right checks
Before chasing the network side, start with the basic system checks and follow a structured diagnostic approach. If other codes are present, do not diagnose this one in isolation. Handle the multiple-code network diagnostic order first so you do not get pulled down the wrong path. Then, before continuing with U0122, check the power and ground circuit for the VSA modulator-control unit. This code can set if that unit does not start normally, and a power or ground problem can make it look like a communication failure.
Understand the failure logic
The body control module is looking for specific data from the VSA modulator-control unit. If that data is not received, the body control module determines there is an abnormality and stores U0122. Once the VSA power and ground check is handled, the diagnostic path moves into the F-CAN lost communication checks for the CAN bus connection to the CAN gateway. If that communication path is not available to test from, pause, recheck the earlier diagnostic path, and avoid guessing at network circuit tests.
Confirmation check
For the confirmation portion, turn the vehicle to the ON mode. Then wait for at least 6 seconds. That gives the modules time to communicate and allows this code logic to run under the intended conditions.
Verification and takeaway
Keep verification separate from the fault-finding steps. After any correction made from the proper power, ground, or F-CAN communication path, repeat the confirmation check: vehicle in ON mode, wait for at least 6 seconds, and confirm U0122 does not reset. Bottom line: prove the VSA modulator-control unit can power up normally, then prove the body control module can receive its network data. For more diagnostic training, visit stepdiagnostics.com.
Final check
U0122 is often approached by proving the VSA modulator-control unit powers up correctly first, then following the communication path until the missing data link is confirmed.
For more guided automotive diagnostics, visit STEP Diagnostics.
