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P0871 OBD-II Trouble Code: Transmission Fluid Pressure Sensor/Switch C Circuit Range/Performance

diagnostic check engine light

P0871 code definition

The P0871 code identifies a problem with the pressure of the fluid inside of the transmission.

The P0871 code is often associated with the P0867, P0868, P0869, P0870, P0872, P0873, P0874, P0875, P0876, P0877, P0878, and P0879 codes.

What the P0871 code means

P0871 is the OBD-II generic code for a fault involving the pressure of the fluid inside of the transmission. This could mean that there is too much pressure inside of the transmission or that there is not enough pressure inside of the transmission. Often, a lack of transmission fluid pressure is caused by a lack of transmission fluid. If fluid has leaked out or otherwise escaped due to a mechanical failure, then there will not be adequate fluid levels inside of the transmission for proper operation.

What causes the P0871 code?

The P0871 code has a number of common causes:

  • Low transmission fluid
  • Faulty transmission high pressure pump
  • Broken or dirty transmission temperature sensor
  • Slipping or malfunctioning transmission
  • Faulty powertrain control module
  • Overheating engine

What are the symptoms of the P0871 code?

The P0871 code will inevitably cause the Check Engine light to illuminate on the vehicle’s dashboard. Around this same time, the smell of overheated transmission may become noticeable. The smell is similar to that of burning oil. Accompanying this may also be smoke from the transmission area, though this only occurs if there is actively leaking fluid in the area.

An improper fluid level may also cause rough shifting and transmission slippage. Automatic transmissions may have trouble shifting at the proper times.

How does a mechanic diagnose the P0871 code?

A mechanic will diagnose the P0871 code with an advanced OBD-II code scanner that can retrieve the factory readings from the vehicle. The certified technician will view the trouble codes in real time and see exactly when the P0871 code was stored. Then the code will be reset and the vehicle will be taken for a test drive.

If the code appears again during the test drive, then the transmission fluid pressure is the likely culprit. Wiring will be tested using a multimeter and the factory test points of the circuits surrounding the transmission. The technician will also check for loose, damaged, or corroded wiring around the transmission sensor circuitry. They will also check the transmission for visible fluid leaks.

Common mistakes when diagnosing the P0871 code

There are a number of mistakes that commonly arise when the P0871 code appears. Sometimes the technician will under-react and simply fill or replace the fluid in instances when the transmission needs to be rebuilt to function properly. Other times, the transmission itself is totally fine and the fluid itself is low or too old to be useful. An overheating transmission is a serious problem, and because of this, servicing an overheating transmission often involves taking the transmission out completely. This is not always necessary.

How serious is the P0871 code?

The P0871 code can be quite serious. It can indicate that the transmission is about to overheat or otherwise fail. The only way to avoid major repairs after the P0871 code is to get the vehicle serviced right away. If that is done, then there is a chance that the problem can be solved relatively inexpensively and quickly. Either way, the problem should be diagnosed as soon as the P0871 code appears.

What repairs can fix the P0871 code?

The most common repairs to address the P0871 code are as follows:

  • Transmission high pressure pump repair or replacement
  • Transmission temperature sensor replacement
  • Replace or repair damaged or corroded wiring
  • Powertrain control module repair or replacement
  • Transmission fluid replacement
  • Rebuild transmission

Additional comments for consideration regarding the P0871 code

The P0871 code can vary a lot as far as severity is concerned. The problem could be a simple lack of fluid, or it could indicate a serious mechanical failure of the transmission. The only way to find out is to have the problem diagnosed by a qualified technician.

Need help with a P0871 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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