Transmission Fluid Pressure Sensor/Switch C Circuit Range/Performance
What it means
P0871 means the transmission fluid pressure (TFP) sensor/switch 'C' signal is present but implausible — its reading doesn't match expected line pressure for the operating conditions. The transmission controller relies on this value to time gear changes, so a range/performance fault can cause harsh or slipping shifts and, over time, overheating.
Can I keep driving? Engine starts, but shifting may be harsh, delayed, or slip — drive gently and repair soon to avoid transmission damage and overheating.
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
- Harsh or delayed shifting
- Transmission slipping
- Check-engine light on
- Transmission overheating
- Reduced fuel efficiency
Common causes
Most likely first
- Faulty TFP sensor/switch C (drifting or inaccurate reading)Likely
- Corroded or damaged sensor wiring or connectorsCommon
- Low or contaminated transmission fluid, or a valve-body/pressure issueCommon
- Faulty transmission control module (TCM)Less often
How to diagnose & fix
Work through it in order
- Check transmission fluid level and condition first.
- Read freeze-frame data and compare the sensor's reported pressure against a mechanical gauge reading.
- Inspect the sensor connector and wiring for corrosion or damage.
- Replace the TFP sensor/switch C if it reads inaccurately; address valve-body or TCM issues only if the sensor and wiring are good. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0871?+
Can I just clear P0871?+
Related codes
Read & clear P0871 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.