P0848 Code: Trouble In Transmission Fluid Pressure Sensor

One of the most important components of the automatic transmission is the fluid sensor, whose main task is to take a reading of the pressure at which the fluid flows. The information received by the sensor is converted into an input signal that is provided to the Powertrain Control Module (PCM) to determine the pressure in the transmission when making gear changes.

But what happens when the sensor finds a very high pressure? The first thing we can notice on the car's dashboard is that the engine check light comes on. It´s the first alert for the driver to take his vehicle to the mechanic.

After a review with the scanner, the mechanic will find the OBD-II code P0848. In this new post from the Sun Transmissions blog we will tell you it’s meaning and how to fix it.

What does the OBD-II code P0848 mean?

The OBD-II code P0848 means that the PCM found a very high voltage on the TFP sensor circuit B, which is above the allowable levels for the transmission.

The main cause of the OBD-II P0848 code is damage, especially to the transmission fluid pressure sensor (TFPS) circuit wires.

Typically, the TFPS is attached to the side of the valve within the transmission system. On some models it is bolted to the side of the transmission case. From there it finishes it´s task by transforming the mechanical pressure of the transmission into an electrical signal that the PCM can easily read.

The Transmission Control Module (TCM) is another component that must receive the electrical signal from the TFPS sensor. Both vehicle computers determine the pressure with which the transmission operates while driving and when making gear changes. In turn, they inform other drivers using the vehicle's data bus.

This means that if a P0848 code appears, the electrical problem wouldn´t only affect the transmission but could damage other systems in the vehicle.

Causes of the P0848 code

The automatic transmission needs adequate pressure to shift gears correctly and for the torque converter to engage and disengage at the appropriate times. This applied pressure on the hydraulic pump is controlled by the PCM through the electronic solenoids. 

Therefore, within the causes for which the P0848 code can be generated are:

• Faulty electronic pressure control solenoids
• Blockage within the hydraulic lines of the transmission.
• Defective or damaged sensor
• Dirty, contaminated or burnt transmission fluid
• Low transmission fluid level 

In some cases, although not very frequent, the fault is in the TCM itself. 

Symptoms that accompany the P0848 code

In some cases, the car does not have any problem that is apparently related to the transmission. For example, there may be a reduction in the efficiency of fuel consumption. 

In other situations, besides the obvious sign of the light on in the check engine, there could be problems with gear changes, failure to start or overheating in the transmission.

Diagnostic Code P0848

To diagnose an automatic transmission problem, the mechanic should use a scanner to read the codes, along with a digital volt/ohmmeter, manual pressure gauge, hydraulic pressure diagram, manufacturer's wiring diagram, among other tools to be able to check the transmission.

One of the first actions is to check the transmission fluid level, as well as the fluid´s condition and odor. If it´s abnormal, has a burning smell or is at a low level, the mechanic should remove the transmission pan in search of fluid remains.

If the transmission fluid is good, the mechanic should inspect the wiring, connections, and related components to make sure they are in good condition. The mechanic should also check the condition of the sensor, hydraulic pump, pressure control solenoid, TCM, and PCM.

Once the situation causing the P0848 code has been repaired, the mechanic should clear the codes stored in the vehicle and perform a performance test. For this, you need to let the car come up to normal operating temperature to see if the code reappears.

It is very important to take the car to a specialized mechanic, who has diagnostic tools such as a scanner, since a common mistake when diagnosing the P0848 code is to think that it´s a mechanical failure of another component.

Find your spare parts at Sun Transmissions

In the Sun Transmissions online store, you will find a wide variety of automatic transmission parts that you can purchase with a few clicks, from a piston, transmission overhaul kits, power steering parts, connectors, automatic transmission clutch, to a transmission solenoid or more. If you have questions or need more information about our products, contact us through the online chat where our advisors are ready to assist you!