P0871
Transmission Fluid Pressure Sensor/Switch C Circuit Range/Performance
Transmission / hydraulic control
Generic OBD-II
Medium
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.
Medium
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.
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?+
Drive gently and briefly. Slipping and overheating can damage the transmission, so have it checked promptly.
Can I just clear P0871?+
It clears, but returns unless the sensor, wiring, or pressure problem is repaired.
Related codes
Often seen with P0871
Read & clear P0871 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX