P0848 Code: Transmission Fluid Pressure Sensor/Switch “B” Circuit High

The transmission fluid pressure sensor measures the hydraulic fluid pressure inside the transmission. Using the readings from this sensor, the transmission control module (TCM) or powertrain control module (PCM) adjusts various outputs to ensure the efficient operation of the transmission.

If the PCM or TCM finds a problem with the transmission fluid pressure sensor or its circuit, its diagnostics will log a P0848 code.

What Does the P0848 Code Mean?

Diagnostic trouble code (DTC) P0848 indicates “Transmission Fluid Pressure Sensor/Switch “B” Circuit High.”

Hydraulic fluid applies pressure inside the transmission. The transmission fluid pressure sensor converts that pressure into an electrical signal and sends it to the TCM or PCM.

When other controllers need the readings from the TFP sensor to operate, the PCM will share the information over the data communication bus.

The PCM will use the data to determine the right transmission operation pressure or timing for when the transmission shifts between gears. In technical terms, this is the “B” input.

The PCM regularly checks the transmission fluid pressure sensor and compares the “B” input readings with the normal operating voltages programmed into its memory. If the signal’s voltage doesn’t match the correct values, the computer will set the powertrain and engine code P0848.

P0848 often (but not always) concerns the electrical circuit.

Note: The definition of code P0848 can differ according to the vehicle manufacturer. Check the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of a Code P0848?

• Low transmission fluid level
• Bad transmission fluid pressure sensor
• Problems with the transmission fluid pressure sensor wiring
• Faulty TCM
• Internal valve body or transmission problems

What are the Common Symptoms of a Code P0848?

• Illuminated check engine light
• More fuel consumed
• Transmission doesn’t shift between gears correctly

How to Diagnose the P0848 Code

Many vehicle makes and models can develop issues that might lead to the PCM or TCM issuing a P0848 code. The exact reason behind the powertrain code can vary on a case-by-case basis, so there is no single approach that can diagnose it.

If you lack the confidence to run a diagnostic test on your vehicle’s transmission fluid pressure sensor, it’s best to take it to an auto repair shop. Otherwise, you can diagnose the issue yourself. To give you a better idea of what to do and expect, here is a helpful video on checking the P0848 code:

How to Fix the P0848 Code

You will need the right tools and know-how to evaluate the transmission fluid pressure sensor and other parts covered by the P0848 code. If you don’t have those, it’s best to leave the job to professionals.

DIYers with advanced technical knowledge and hands-on experience can consult a vehicle-specific repair manual or online repair database to make their task easier.