P0871 code meaning
Transmission Fluid Pressure Sensor/Switch C Circuit Range/Performance
Powertrain system Generic code P08xx codes Check engine light
What P0871 means
Transmission fluid pressure switches C and D report whether a clutch circuit is pressurised. They are more widespread than A and B: GM's 6L80/6L90 and 6T40/6T70 six-speeds put switch C on the 2-6 brake and D on the 1-2-3-4 clutch, Allison uses them for its third shift valve and its reverse switch, Ram's RFE gearboxes for the clutch pressure switches in the solenoid block. Ford reports pressure faults under its solenoid codes. P0871 means the switch does not follow the command or gear. On Ram's RFE it is the overdrive clutch switch: open in gears 1 to 3, closed in 4 to 6; it closes at about 1.5 bar and opens at 0.75 bar. Sonnax blames worn valve body bores in about 90 % of cases; on 2024 trucks it came with P0868 from a broken rear thrust washer. Allison 2006: switch without pressure 5 s after command, type A.
P0871 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 12 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0871
- MIL or transmission warning lamp on
- Limp mode, often in 2nd or 3rd gear
- Harsh engagement, neutral feeling in 4th gear
Common causes of P0871
- Most likelyWorn valve body bores or shift valve plugs
- PossibleMechanical damage: thrust washer, clutch seals
- PossiblePressure switch faulty (lip seal)
- PossibleDirt or sticking valve (dual clutch)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Transmission fluid pressure sensorTransmission valve bodyTransmission wiringTransmission control module
What each part of P0871 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 8 | Area: transmission. |
| 71 | The exact fault in that area. |
What to do next
- Note P0871 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0871
What does P0871 mean?
P0871 means "Transmission Fluid Pressure Sensor/Switch C Circuit Range/Performance". Transmission fluid pressure switches C and D report whether a clutch circuit is pressurised. It is a generic code, so it means the same on every make.
Is it safe to drive with P0871?
Drive gently and only to a workshop. With P0871 the car can go into limp mode (reduced power) to protect itself.
Will P0871 fail an emissions test?
Yes, it can. P0871 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0871 to fix?
Difficulty: hard. A typical repair takes 1 to 12 hours of work. This is a job for a workshop.
Will P0871 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.