What this code means
U128D means the blind spot information radar unit may not be receiving an expected gauge control module message over the B-CAN network.
What the vehicle may do
- The blind spot information system may show a warning or may be disabled.
- The code may store when the gauge control module does not start normally.
- The code can appear when communication between modules is interrupted.
Possible fault areas
- Possible B-CAN communication concern between the blind spot information radar unit and the gauge control module.
- Possible gauge control module startup concern.
- Possible gauge control module power or ground circuit concern.
Diagnostic path
Opening context
Today we’re looking at U128D on a 2020 to 2025 Honda CR-V Hybrid. In plain terms, this code means the blind spot information radar unit may not be getting the gauge control module messages it expects over the B-CAN network. The driver may see blind spot information warnings, the system may be disabled, or the fault may simply be stored after a communication problem. Broadly, this can involve a possible network communication issue, a gauge control module startup problem, or a possible power or ground problem feeding the gauge control module.
Start with the right checks
Before chasing the blind spot radar unit, start with the basic system checks and follow a structured diagnostic approach. The important caution on this one is that U128D may set if the gauge control module does not start normally. Also, a power or ground circuit failure at the gauge control module can set this code, so check the gauge control module power and ground side first before going deeper into the B-CAN communication path.
What sets the code
The fault logic is straightforward: if the BSI radar unit cannot receive the gauge control module signals over B-CAN, it treats that as an abnormal condition and stores U128D. So the diagnosis should stay focused on why that message is missing, not on replacing parts by assumption.
Confirmation step
To confirm the condition, turn the vehicle to the ON mode, then wait for at least 5 seconds. That gives the modules time to come online and gives the communication fault a chance to appear under the expected conditions.
Diagnostic direction
If U128D returns after that, keep the testing centered on the B-CAN lost communication path between the BSI radar unit and the gauge control module. If other codes are present, check what they mean first, because they may point you toward a module startup, power, ground, or network issue that explains the missing message.
Verification
After any correction is made, verify the repair and confirm the code stays gone under the same operating condition: vehicle ON, modules awake, and the communication path active. The key is to prove the BSI radar unit can receive the gauge control module signal consistently, not just clear the code once.
Takeaway
Bottom line: U128D is a B-CAN message-missing problem for the blind spot radar unit, and the smart first move is to make sure the gauge control module is powering up correctly before chasing the rest of the communication path. For more diagnostic training, visit stepdiagnostics.com.
Final check
U128D should be approached as a missing B-CAN communication signal concern, with gauge control module startup, power, and ground checks kept early in the diagnostic path.
For more guided automotive diagnostics, visit STEP Diagnostics.
