What this code means
U0038 may indicate an F-CAN BUS-OFF communication concern involving the ICM, where the module may not be communicating normally on the DF-CAN B network.
What the vehicle may do
- The vehicle may show network-related warning lights.
- Some module data may be missing or inconsistent.
- Other communication-related symptoms can occur depending on which systems are affected.
Possible fault areas
- Communication network wiring or connectors may be involved.
- Module power or ground conditions can be possible contributors.
- The ICM side of the communication path may be involved.
Diagnostic path
Opening context
On this 2018 to 2025 Honda Accord Hybrid, U0038 points to an F-CAN BUS-OFF type communication problem involving the ICM. In plain language, the ICM may not be able to communicate normally on the DF-CAN B network. The vehicle may show network-related warning lights, missing data, or other module communication symptoms. The broad possible fault areas can include the communication network, connector or wiring issues, module power or ground concerns, or the ICM side of the network path.
Start with the basic approach
Before getting into the code-specific check, start with the basic system checks and follow a structured diagnostic approach. If other codes are present, understand what they are telling you first, especially if they point to a broader network or power supply issue. For this code, the logic is simple: if the ICM cannot send a signal to another unit over DF-CAN B, it judges that as abnormal and stores U0038.
Reproduce the monitor condition
To confirm the condition, turn the vehicle to the ON mode and wait 6 seconds. That is the available confirmation step for this DTC. During that key-on window, the ICM communication monitor has the opportunity to decide whether it can transmit normally on DF-CAN B.
Testing boundary
The next detailed BUS-OFF pinpoint path is not available here, so do not guess and do not jump straight to parts. Pause, recheck the earlier diagnostic path, confirm the basic network checks are being handled in the right order, and continue only with the correct ICM BUS-OFF testing path.
Verification and takeaway
Keep verification separate from testing. After any confirmed correction from the proper BUS-OFF diagnostic path, bring the vehicle back to the same ON-mode confirmation condition and make sure U0038 does not return. The takeaway: U0038 is a communication-path code for the ICM on DF-CAN B, so confirm the monitor condition first, then use the proper BUS-OFF path instead of guessing at components. For more diagnostic training, visit stepdiagnostics.com.
Final check
U0038 is often approached as a network communication concern: confirm the monitor condition, then continue with the proper BUS-OFF diagnostic path.
For more guided automotive diagnostics, visit STEP Diagnostics.
