What this code means
P1109 may mean the ECM/PCM is seeing a barometric pressure input that appears too high or not plausible for the operating conditions.
What the vehicle may do
- The vehicle may run normally with only a warning light.
- It can have possible drivability or emissions-related symptoms depending on when the fault occurs.
Possible fault areas
- Possible BARO signal plausibility issue
- Possible PCM software concern
- Possible scan-tool data confirmation issue
- Possible PCM-related fault
Diagnostic path
Opening context
On this 2010 to 2016 Honda CR-V with the 2.4 gas engine, P1109 is for a BARO sensor circuit reading that is out of range on the high side. In plain language, the ECM/PCM is seeing a barometric pressure signal that may not look believable for the conditions. The vehicle may run normally, or it may have drivability or emissions-related symptoms depending on when the fault shows up. The possible fault areas can include BARO signal plausibility, PCM software, scan-tool data confirmation, or a PCM-related problem. Before you chase the code, start with the basic system checks and the general troubleshooting information.
Verify the code
Start the P1109 check by turning the vehicle to the ON mode. Then use the HDS to clear the DTC. After the code is cleared, use the HDS again and check for pending or confirmed DTCs. The key question is simple: does P1109 come back as indicated or not?
If P1109 is indicated
If P1109 is indicated after clearing and rechecking, the failure has been duplicated. At that point, the diagnostic path moves to the PCM side. Update the PCM if it does not have the latest software, or substitute a known-good PCM, then recheck the code. If P1109 goes away after the PCM update, troubleshooting is complete. If P1109 goes away only with the known-good PCM substituted, replace the original PCM.
If P1109 is not indicated
If P1109 is not indicated after the clear and recheck, treat it as an intermittent failure and the system is OK at this time. If freeze data or an on-board snapshot was recorded for this DTC, try to reproduce the captured conditions instead of guessing at a repair.
Verify the repair
Keep verification separate from the test path. After a PCM update, PCM substitution, or any intermittent-condition check, verify the repair and confirm P1109 stays gone under the conditions you can reproduce. The takeaway is that this chart is short: clear it, see whether P1109 returns, and if it does, follow the PCM software or known-good PCM path exactly. For more diagnostic training, visit stepdiagnostics.com.
Final check
For this diagnostic path, first verify whether P1109 returns after clearing it, then follow the PCM software or known-good PCM branch only if the failure is duplicated.
For more guided automotive diagnostics, visit STEP Diagnostics.
