Intermediate Shaft Speed Sensor A Circuit
What it means
P0791 means the control module has detected a circuit problem with the intermediate shaft speed sensor. The transmission uses this sensor to compare shaft speeds and confirm it is in the right gear, so a bad signal can cause erratic or delayed shifts and may force a protective limp mode. It's a sensor fault — it affects shifting, not engine starting.
Can I keep driving? Often driveable but shifting may be erratic or the transmission may limp — drive gently to a shop; it won't stop the engine from starting.
Real-world scan data
Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.
Common symptoms
What you'll notice
- Erratic, delayed, or harsh shifting
- Transmission slipping or dropping into limp mode
- Wrong-gear engagement
- Check-engine light on
Common causes
Most likely first
- Failed intermediate shaft speed sensorLikely
- Damaged wiring or corroded connector in the sensor circuitCommon
- Debris or damage on the sensor's tone/reluctor ringCommon
- Loose or corroded electrical connectionsLess often
- Failed transmission control module (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and compare the intermediate shaft speed reading against input/output speeds in live data.
- Inspect the sensor wiring and connector for damage or corrosion.
- Check the sensor tip and tone ring for metal debris or damage.
- Measure the sensor and its circuit; replace the sensor if it reads open, shorted, or erratic.
- Clear the code and road-test to confirm normal shifting returns.
FAQ
Quick answers
Is it safe to drive with P0791?+
Can I just clear P0791?+
Related codes
Read & clear P0791 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.