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.