P0871 - TRANSMISSION FLUID PRESSURE SENSOR / SWITCH "C" CIRCUIT RANGE / PERFORMANCE

The transmission fluid lubricates the moving components and protects against possible friction damage. As the vehicle accelerates, the transmission fluid pump increases hydraulic pressure. This is observed by a transmission oil pressure switch, which reads the amount of pressure and then sends that information to the vehicle’s computer, which is used by the computer to know if the clutch should be engaged for shifting.

 P0871 OBDII diagnostic code indicates that a transmission fluid pressure problem has occurred. This code means that the pressure inside the transmission is not within the parameters set by the manufacturer, perhaps caused by a lack of fluid. This particular code is a frequent fault present in a large number of vehicles. So we will not only see this DTC fault in cars from a single manufacturer, but it will also be present in other vehicle manufacturers around the world.

The P0871 code can be quite serious. It can indicate that the transmission is about to overheat or fail. The only way to avoid major repairs after this code is to have the vehicle serviced immediately. If that is done, 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.

• Check Engine light illumination.
• Abrupt or erratic transmission shifts.
• Transmission overheats.
• You may notice smoke coming from near the transmission.

However, there are a series of errors that often arise when the P0871 code is encountered. Sometimes, the technician will underreact and simply fill or replace the fluid in cases where the transmission must 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, repairing an overheating transmission often involves removing the transmission entirely. This is not always necessary. That’s why you should always make sure that your vehicle is being checked by a professional that knows how to detect and solve this particular code fault.

The reasons for setting the P0871 OBD2 trouble code are:

• Possibly the transmission fluid level is below the required level.
• The transmission high-pressure pump may be defective.
• The Transmission Fluid Pressure sensor (TFP) could be defective.
• The transmission may be malfunctioning due to mechanical malfunctions.

If you do not have mechanical knowledge, it is recommended that you go to the nearest garage in your city, and let a professional be the one who puts a solution and eliminates this code from your vehicle.  A mechanic professional will troubleshoot the P0871 code with an experienced OBD-II code scanner that can restore the vehicle's factory readings. The qualified technician will display the trouble codes in real-time and look precisely at when the P0871 code was set. The code will then be re-established and the vehicle will be put through a test drive.

If the code pops up again while test driving, then transmission fluid pressure is the probable fault. The wiring will be checked out using a multimeter and the factory test points of the circuits that surround the transmission. The mechanic will also inspect for loose, corrupted, or faulty wiring around the transmission sensor circuits. It is also important to check the transmission for visible fluid leaks.

If, on the other hand, you have the necessary knowledge to correct this fault, you can use some tools such as certified OBD2 meters that will help you to remove this message or alert from your vehicle's dashboard. Read on and buy the model that best suits your car's requirements.  Here are some useful steps that you should follow when storing the DTC P0871 OBDII fault code:

• Verify that the transmission fluid level is necessary for a good operation of the system. If you find an excessively low level, check for leaks. Repair such leaks if necessary and provide the missing fluid.
• Check all wiring in the system for damage or poor connections. Use a multimeter to check that the actual values are as stated by the manufacturer in the specifications. Repair or replace as required.
• Inspect the transmission high-pressure pump and verify that it is functioning properly. If you find a defect in the pump, proceed to replace it.
• Replace the Transmission Fluid Pressure Sensor.