What this code means
P1780 may indicate that the PCM has detected one or more automatic transmission shift-control system faults.
What the vehicle may do
- The vehicle may go into a transmission default strategy.
- The transmission may not shift normally.
- The issue may appear during a drive cycle when the transmission is commanded through its normal gear changes.
Possible fault areas
- Possible stored-code context in the automatic transmission shift-control system.
- Possible PCM software status concern.
- Possible PCM control issue if the diagnostic path supports checking with a known-good PCM.
Diagnostic path
Set up the P1780 diagnosis
On this 2010 to 2015 Honda Civic with the 1.8 gas engine, P1780 is a shift control system code. In plain language, the PCM may be seeing one or more automatic transmission shift-control faults, and the vehicle may go into a default transmission strategy or may not shift normally. The broad areas to keep in mind are the stored code context, the shift-control side of the automatic transmission system, and PCM software or PCM substitution only if the code path gets you there. Before you troubleshoot, save all freeze data and any on-board snapshot with the HDS, then start with the basic system checks.
Clear the code and reproduce the shift event
Start by turning the ignition switch to ON (II). Clear the DTC with the HDS. Then test-drive the vehicle with the shift lever in D, and let the transmission shift through all five gears. The goal here is to put the transmission back through the operating condition that can make P1780 show itself again.
Check whether P1780 is alone
After the drive, check the HDS for any other Pending or Confirmed DTCs indicated along with P1780. If other codes are present, do not treat P1780 as the only problem. Follow the troubleshooting for the indicated code first. If P1780 is alone, then the path moves to the PCM side: update the PCM if it does not have the latest software, or substitute a known-good PCM, then move on and verify the repair.
Verify the repair with the monitor result
To verify the repair, test-drive the vehicle again with the shift lever in D, and let the transmission shift through all five gears. Then monitor the OBD STATUS for P1780 in the DTCs MENU with the HDS. The result will be PASSED, FAILED, or NOT COMPLETED.
Use the OBD STATUS result correctly
If the HDS indicates PASSED, troubleshooting is complete. If a PCM was substituted, replace the original PCM. After that, check for other DTCs; if any other Pending or Confirmed codes are present, follow the troubleshooting for those codes. If the HDS indicates FAILED, go back to the beginning and recheck the path. If the PCM had been updated, substitute a known-good PCM and check the OBD STATUS again. If the HDS indicates NOT COMPLETED, meet the test condition and check the OBD STATUS again.
Takeaway
The key with P1780 is not to guess at transmission parts. Save the data, clear the code, drive it through all five gears, see whether P1780 is alone, and use the HDS OBD STATUS to confirm the direction. For more diagnostic training, visit stepdiagnostics.com.
Final check
P1780 often needs a code-context check and a proper verification drive before drawing conclusions.
For more guided automotive diagnostics, visit STEP Diagnostics.
