What this code means
U0155 may mean the PCM is not receiving expected communication from the gauge control module, or the information from that module may be abnormal.
What the vehicle may do
- The vehicle may show gauge or warning-display issues.
- The code can be stored with limited obvious symptoms.
- Communication-related warning behavior may vary by vehicle condition.
Possible fault areas
- Gauge control module power and ground circuits
- Gauge control module startup behavior
- PF-CAN communication path between the PCM and gauge control module
- Gateway-related communication path
Diagnostic path
Opening context
U0155 on this Honda Civic is a PF-CAN communication fault between the Powertrain Control Module and the gauge control module. In plain language, the PCM may not be receiving the expected message from the gauge control module, or the message it receives may be abnormal. The vehicle may show gauge or warning-display issues, or it can store the code with only limited driver symptoms. For this code, keep the diagnosis focused on the gauge control module starting up normally, its power and ground circuits, and the PF-CAN communication path between the modules.
Start with the basic checks
Before chasing the network side, start with the basic system checks and follow a structured diagnostic approach. If other faults are present, check what they mean first so you do not get pulled into a communication diagnosis that is being caused by a more basic power, ground, or module-startup problem.
Check gauge control module power and ground first
The first directed check for U0155 is the power and ground circuit for the gauge control module. That matters because this code may set if the gauge control module does not start normally, and it may also set from a gauge control module power or ground circuit failure. Do that check before treating the PF-CAN line as the primary suspect.
Move into the PF-CAN communication path
After the gauge control module power and ground check, the diagnostic path moves to the PF-CAN lost-communication path through the gateway connection. The detailed branch testing for that path is not included here, so do not guess at connector checks, resistance checks, or module calls. Pause, recheck the earlier diagnostic path, and continue only with the correct PF-CAN lost-communication procedure for the gateway connection.
Verify the repair
Keep verification separate from the testing. To confirm the code behavior, turn the vehicle to the ON mode and wait 6 seconds. Then confirm U0155 does not reset under that confirmation step before calling the repair complete.
Takeaway and CTA
The key takeaway is simple: for U0155, prove the gauge control module can power up correctly before you condemn the network, then follow the PF-CAN communication path in order and verify the code stays gone. For more diagnostic training, visit stepdiagnostics.com.
Final check
This diagnosis often starts with basic module power and ground checks, then moves into the PF-CAN communication path if those checks do not explain the fault.
For more guided automotive diagnostics, visit STEP Diagnostics.
