What this code means
U0155 may indicate a communication problem between the PCM and the gauge control module on the F-CAN network.
What the vehicle may do
- The vehicle may show warning indicators or abnormal gauge behavior.
- Scan-tool data may show communication-related symptoms.
- The problem can be intermittent if the code does not return during verification.
Possible fault areas
- Possible F-CAN wiring opens or connection issues.
- Possible poor connections or loose terminals at the PCM or gauge control module.
- Possible gauge control module-side concern after the specified wiring checks pass.
Diagnostic path
What U0155 is telling you
On this 2010 to 2017 Honda Accord with the 2.4 gas engine, U0155 points to an F-CAN communication problem between the PCM and the gauge control module. In plain terms, the PCM may not be seeing gauge control module communication the way it should. The vehicle may show warning lights, gauge issues, or scan-tool communication symptoms, and the possible fault areas can include the network wiring, connector or terminal condition at the PCM and gauge control module, or a module-side problem after the wiring checks pass. Before you start, record the freeze data and any on-board snapshot, then start with the basic system checks.
Verify the fault first
Begin by turning the ignition switch to ON (II), or pressing the engine start/stop button to select ON mode. Clear the DTC with the HDS, then check again for Pending or Confirmed DTCs. If U0155 comes right back or is still indicated, the fault is duplicated and you move into the gauge control module side of the diagnostic path. If U0155 is not indicated, treat it as an intermittent at this time. The system is OK right now, so concentrate on poor connections or loose terminals at the gauge control module and the PCM.
Use the gauge module codes to decide the next move
Next, check the gauge control module for DTCs with the HDS. Do not get distracted by reading every related code out loud here; the point is to see whether the gauge module is also flagging communication trouble with the same network path. If those related communication codes are indicated, continue to the F-CAN wire checks. If they are not indicated, the next move is the gauge control module input test.
Check the F-CAN-H circuit for an open
Now power the vehicle down. Turn the ignition switch to LOCK (0), or press the engine start/stop button to select OFF mode. Jump the SCS line with the HDS. Disconnect PCM connector A, the 51P connector, and disconnect gauge control module connector A, the 32P connector. With both connectors disconnected, check continuity on the F-CAN-H circuit between gauge control module connector A 32P terminal No. 19, WHT, and PCM connector A 51P terminal No. 2, WHT. If there is continuity, the F-CAN-H wire is OK and you continue to the F-CAN-L check. If there is no continuity, repair the open in the F-CAN-H wire between PCM A2 and the gauge control module, then verify the repair.
Check the F-CAN-L circuit for an open
Keeping the same test condition — ignition in LOCK (0) or OFF mode, PCM connector A 51P disconnected, and gauge control module connector A 32P disconnected — check continuity on the F-CAN-L circuit. Test between gauge control module connector A 32P terminal No. 20, RED, and PCM connector A 51P terminal No. 1, RED. If there is no continuity, repair the open in the F-CAN-L wire between PCM A1 and the gauge control module, then verify the repair. If continuity is present, the F-CAN-L wire is OK. At that point, substitute a known-good gauge control module and run the repair verification. If U0155 is not indicated after the substitution, replace the original gauge control module, then verify the repair again.
Verify the repair and confirm the code stays gone
For verification, reconnect all connectors and exit SCS mode with the HDS. Turn the ignition switch to ON (II), or press the engine start/stop button to select ON mode. Reset the PCM with the HDS, then do the PCM idle learn procedure. After that, check for Pending or Confirmed DTCs with the HDS. If U0155 is still indicated, check again for poor connections or loose terminals at the gauge control module and the PCM, then go back to the beginning of the diagnostic path. If U0155 is not indicated, this troubleshooting path is complete. If other codes are present, check what they mean next.
Takeaway
The key on U0155 is to prove the code first, use the gauge module results to choose the path, then isolate the F-CAN-H and F-CAN-L circuits before condemning a module. Keep verification separate from testing, and make sure the code stays gone before calling it fixed. For more diagnostic training, visit stepdiagnostics.com.
Final check
Diagnose U0155 by confirming the fault, checking the related gauge module communication status, testing the F-CAN-H and F-CAN-L circuits in order, and then verifying that the code stays gone.
For more guided automotive diagnostics, visit STEP Diagnostics.
