What this code means
U0038 may indicate that the PCM cannot send a communication signal to another unit over the PT-CAN network.
What the vehicle may do
- The vehicle may show warning lights.
- Some systems may not communicate normally.
- The vehicle may have limited or abnormal system operation depending on which modules are affected.
Possible fault areas
- Possible CAN communication wiring or connector concerns.
- Possible network communication or gateway-related concerns.
- Possible module communication concerns.
Diagnostic path
Opening context
On this 2016 to 2024 Honda Civic with the 2.0 gas engine, U0038 is a network communication code in the PGM-FI system. In plain language, the PCM may be seeing that it cannot send a message to another control unit over the PT-CAN network. The vehicle may have warning lights, limited system operation, or other modules that do not communicate normally. Possible fault areas can include the CAN communication path, connectors, wiring integrity, module communication, or gateway-related network behavior. Treat this as a communication diagnosis, not as a single-sensor code.
Start with the basic checks
Before digging into the network, start with the basic troubleshooting routine. Make sure the symptom and code information are understood, and if other codes are present, check what they mean first. For this code, the key setting logic is simple: if the PCM cannot send a signal to another unit through the PT-CAN, it judges that as abnormal and stores U0038.
Follow the CAN bus-off path
After the basic checks, move into the CAN bus-off diagnostic path for a network that is not communicating through the CAN gateway. Keep the focus on proving the communication path instead of guessing at parts. The job here is to find out why the PCM message is not getting out across the network the way it should.
Reproduce the monitor condition
To run the confirmation step, turn the vehicle to the ON mode, and wait 6 seconds. That short ON-mode window is the monitor gate for this check, so use it consistently when you are confirming whether the fault is still active.
Verification and takeaway
Keep verification separate from the network testing. Once the communication diagnosis and any supported repair are complete, use the ON-mode confirmation window again and make sure U0038 stays gone. The takeaway is straightforward: U0038 is a PT-CAN communication problem from the PCM’s point of view, so follow the CAN bus-off path and prove the network before condemning anything. For more diagnostic training, visit stepdiagnostics.com.
Final check
U0038 should be approached as a network communication diagnosis, with attention on proving the CAN communication path.
For more guided automotive diagnostics, visit STEP Diagnostics.
