What this code means
P0843 may mean the PCM is seeing a high signal from the CVT driven pulley pressure sensor circuit.
What the vehicle may do
- The vehicle may have CVT operation concerns or shift-related complaints.
- The warning light may be on with the code stored.
- The concern can sometimes be intermittent.
Possible fault areas
- A possible pressure sensor circuit issue may be involved.
- Connector condition or wiring between the sensor and PCM can be involved.
- The sensor itself may be involved.
- The PCM side of the circuit may be involved.
Diagnostic path
Code meaning and approach
On this 2010 to 2015 Honda Civic with the 1.8 gas engine and CVT, P0843 means the PCM is seeing the transmission fluid pressure sensor or switch A circuit high. In plain terms, the driven pulley pressure sensor signal may be higher than expected. The car may have shifting complaints, CVT operation concerns, or it may only have the warning light and code stored. The broad fault areas can include the pressure sensor circuit, the sensor connector and wiring, the PCM side of the circuit, or the sensor itself. The key point here is that this diagnostic path treats P0843 as an electrical circuit problem, not a mechanical failure inside the transmission. Before you get deep into pinpoint testing, start with the basic system checks and follow a structured diagnostic approach.
Duplicate the fault first
Start by turning the ignition ON, or selecting ON mode with the engine start stop button. Clear the DTC with the HDS, then watch Driven Pulley Pressure Sensor voltage in the data list. If that value reads 4.84 V or more, the failure is duplicated and you keep going. If it does not, treat it as an intermittent at this moment. The system is OK right now, so use the captured freeze data or onboard snapshot conditions to try to reproduce the same operating conditions before chasing the circuit further.
Separate the PDN line from the rest of the circuit
Next, turn the ignition OFF or select OFF mode. Disconnect the CVT driven pulley pressure sensor 3P connector. Install a jumper between terminal No. 1, the GRN/YEL wire, and terminal No. 2, the BLU/RED wire. Then turn the ignition back ON and check Driven Pulley Pressure Sensor voltage again in the HDS data list. If it still shows 4.84 V or more, move to the PDN line open check. If it no longer shows that high reading, move to the sensor power and ground side checks.
Check the PDN line for an open
For the PDN line check, turn the ignition OFF again, remove the jumper, jump the SCS line with the HDS, and disconnect PCM connector B, the 51P connector. With the CVT driven pulley pressure sensor 3P connector and PCM connector B disconnected, check continuity on the PDN circuit between sensor connector No. 2, BLU/RED, and PCM connector B No. 39, also BLU/RED. If there is continuity, the PDN wire is OK. At that point, update the PCM if it does not have the latest software, or substitute a known-good PCM, then recheck. If P0843 goes away after the update, troubleshooting is complete. If P0843 goes away with the substituted PCM, replace the original PCM. If there is no continuity on that PDN check, repair the open in the PDN wire between the driven pulley pressure sensor and the PCM.
Check the sensor supply and signal ground side
If the earlier jumper test sent you down the other path, turn the ignition OFF, remove the jumper, then turn the ignition ON again. With the CVT driven pulley pressure sensor connector disconnected and PCM connector B disconnected, measure voltage between sensor connector No. 1, GRN/YEL, and sensor connector No. 3, YEL/BLU. You are looking for about 5 V. If about 5 V is present, replace the CVT driven pulley pressure sensor. If about 5 V is not present, continue into the VCC2 line check.
Finish the VCC2 and SG2 open checks
For the VCC2 line check, keep the ignition ON with the CVT driven pulley pressure sensor connector and PCM connector B still disconnected. Measure voltage from sensor connector No. 3, YEL/BLU, to body ground. If you have about 5 V, the VCC2 wire is OK, so repair an open in the SG2 wire between the sensor and the PCM. If you do not have about 5 V, repair an open in the VCC2 wire between the sensor and the PCM.
Final takeaway
The clean way to diagnose P0843 is to prove whether the high signal is present now, use the jumper test to split the fault path, then isolate PDN, VCC2, SG2, the sensor, or the PCM path without guessing. Keep it electrical, follow the voltage and continuity results, and confirm the code stays gone before calling it fixed. For more diagnostic training, visit stepdiagnostics.com.
Final check
This code is handled as a possible electrical circuit fault path rather than a mechanical transmission failure.
For more guided automotive diagnostics, visit STEP Diagnostics.
