What this code means
P0793 may mean the PCM is not receiving the expected speed signal from the intermediate shaft speed sensor A circuit on the CVT.
What the vehicle may do
- The vehicle may have CVT shift or driveability complaints.
- The code may appear during a controlled operating check.
- A warning indicator may be on depending on vehicle conditions.
Possible fault areas
- Possible sensor signal circuit concern.
- Possible sensor feed or ground reference circuit concern.
- Possible connector or wiring issue between the sensor and PCM.
- Possible sensor fault.
- Possible PCM software or PCM-related concern after circuit checks pass.
Diagnostic path
Opening context
On this 2010 to 2015 Honda Civic with the 1.8 gas engine and CVT, P0793 is for the intermediate shaft speed sensor A circuit showing no signal. In plain terms, the PCM may not be seeing the speed signal it expects from that sensor circuit. The vehicle may have CVT shift or driveability complaints, or it may only show the code during a controlled check. The broad fault areas can include the sensor circuit wiring, sensor power and ground reference paths, the sensor itself, or, after the circuit checks pass, PCM software or PCM-related diagnosis. One important point here: this diagnostic is aimed at an electrical circuit problem, not a mechanical failure inside the transmission.
Start with basic checks and reproduce the fault
Before getting into pinpoint testing, start with the basic system checks and make sure the concern is being duplicated. Turn the ignition ON, clear the code with the HDS, then raise the vehicle on a lift. Make sure it is securely supported and that all four wheels can rotate freely. Start the engine, turn VSA off with the VSA OFF button, put the shifter in D, and run the vehicle at speeds over 19 mph (30 km/h) for at least 30 seconds. Then slow down, stop the wheels, and check the HDS for pending or confirmed codes. If P0793 comes back, the failure is duplicated and you move into circuit testing. If it does not come back, treat it as intermittent for now. If captured operating data is available, try to reproduce the concern under those same conditions rather than guessing.
Check the NDR signal line voltage first
With the fault duplicated, turn the ignition OFF and disconnect the CVT drive pulley speed sensor 3-pin connector. Turn the ignition back ON. Check voltage from connector terminal No. 1, the RED/BLU NDR circuit, to body ground. With the connector unplugged and the ignition ON, you are looking for about 5 V. If you have about 5 V on that NDR line, continue to the VCC1 check. If you do not have about 5 V, skip ahead to the NDR short-to-ground check.
Check the VCC1 feed
Next, still with the sensor connector disconnected and the ignition ON, measure from connector terminal No. 3, the YEL/RED VCC1 circuit, to body ground. This check also expects about 5 V. If the VCC1 feed is present, keep going. If it is not present, repair an open in the VCC1 wire between the CVT drive pulley speed sensor and the PCM.
Check the sensor ground reference path
Now check across the sensor connector between terminal No. 2, the GRN/WHT SG1 circuit, and terminal No. 3, the YEL/RED VCC1 circuit. The ignition is still ON and the sensor connector is still disconnected. Again, the expected result is about 5 V. If that voltage is present, the circuit checks to this point support replacing the CVT drive pulley speed sensor. If that voltage is not present, repair an open in the SG1 wire between the CVT drive pulley speed sensor and the PCM.
If NDR voltage was missing, check for a short to ground
If the NDR line did not have the expected voltage back at the first circuit check, turn the ignition OFF. Use the HDS to jump the SCS line, then disconnect PCM connector B, the 51-pin connector. With the sensor connector still disconnected, check continuity between the sensor connector terminal No. 1 RED/BLU NDR circuit and body ground. If there is continuity, repair a short to ground in the NDR wire between the CVT drive pulley speed sensor and the PCM. If there is no continuity, the NDR wire is not shorted to ground, so continue to the open-circuit check.
Check the NDR wire for an open
With the ignition OFF, the sensor connector disconnected, and PCM connector B disconnected, check continuity from the sensor connector terminal No. 1 RED/BLU NDR circuit to PCM connector B terminal No. 44, also RED/BLU. If there is no continuity, repair an open in the NDR wire between the CVT drive pulley speed sensor and the PCM. If there is continuity, the NDR wire checks OK. At that point, update the PCM if it does not have the latest software, or substitute a known-good PCM, then recheck. If P0793 goes away after the update, troubleshooting is complete. If P0793 goes away with the known-good PCM substituted, replace the original PCM.
Closing takeaway
The key on P0793 is to stay electrical and stay in order: duplicate the fault, prove the NDR signal path, prove the VCC1 and SG1 paths, then only move to sensor or PCM conclusions when the test results support it. After the supported repair, verify the repair and confirm P0793 stays gone. For more diagnostic training, visit stepdiagnostics.com.
Final check
This code is often approached as an electrical circuit diagnosis, with mechanical transmission faults not being the focus of this test path.
For more guided automotive diagnostics, visit STEP Diagnostics.
