Skip the auto shop - Our mechanics make house calls

P0848 OBD-II Trouble Code: Transmission Fluid Pressure Sensor/Switch B Circuit High

diagnostic check engine light

P0848 code definition

The storage of a P0848 trouble code means that the powertrain control module (PCM) has detected a problem with the transmission fluid sensor circuit. The pressure to the hydraulic pump is controlled by the PCM via the electronic pressure control solenoids. Some of the other trouble codes a mechanic might also see include P0845, P0846, P0847, and P0849.

What the P0848 code means

A P0848 trouble code signifies that there is a discrepancy in the pressure produced as opposed to what is actually needed by the transmission to function properly. The transmission needs the proper amount of pressure to shift properly and for the torque converter to engage and disengage like it should.

What causes the P0848 code?

Some common causes of a P0848 trouble code include a faulty transmission fluid pressure sensor, bad electronic pressure control solenoid, and blockage within the hydraulic lines of the transmission. Mechanical failure of the transmission can also lead to the storage of this code by the PCM. Mechanical failure can result from a low fluid condition or dirty and contaminated fluid within the transmission. A low fluid condition or dirty transmission fluid can also cause the PCM to store the trouble code. Though rare, another culprit could be the PCM itself.

What are the symptoms of the P0848 code?

In addition to showing no obvious symptoms of a problem at all, other than a lit Check Engine light, when storing a P0848 trouble code, the torque converter in the vehicle could fail to work properly, there could be problems with shifting, and the transmission could overheat. Other symptoms include a reduction in the fuel efficiency of the vehicle and the PCM placing the transmission into Limp-in mode.

How does a mechanic diagnose the P0848 code?

To properly diagnose a P0848 trouble code, a mechanic needs a code reader, digital volt/ohmmeter, manual pressure gauge, hydraulic pressure diagram, and the manufacturer's wiring diagram for the transmission fluid pressure sensor. The mechanic must also perform the following steps:

  • Start by checking the vehicle's transmission fluid, paying particular attention to fluid condition and smell.
  • If the fluid has a burnt smell or looks abnormal, remove the transmission pan and inspect it for the presence of debris, including parts of the clutch. If debris is found, rebuild the transmission before proceeding.
  • Also visually inspect the wiring, connectors, and any related components for damage.
  • Fix any detected leaks before filling the transmission with fluid. Also, clear the P0848 trouble code.
  • Next, the mechanic should start the vehicle and allow it to reach a normal operating temperature before test driving it to see if the code returns.
  • If the code returns, connect a manual pressure pump and using a hydraulic pressure diagram test the pressure produced by the hydraulic pump. The mechanic should then compare their findings to the manufacturer's specifications.
  • If, after clearing the code, it returns, use a wiring diagram from the manufacturer for the transmission fluid pressure sensor and a digital volt/ohmmeter to check the reference voltage and ground signal of the sensor.
  • If the sensor tests as open, disconnect any related control modules and test the circuits related to the transmission fluid pressure sensor for continuity and resistance.
  • The mechanic should also check the reference voltage and ground signal of the electronic pressure control solenoid and PCM with the volt/ohmmeter for fault.
  • Clear the P0848 trouble code and test the vehicle to see if it returns.

Common mistakes when diagnosing the P0848 code

A common mistake when diagnosing a P0848 trouble code is for the mechanic to overlook a faulty transmission fluid pressure sensor, electronic pressure control solenoid, or damaged wiring as the cause of the code and assuming it was stored in conjunction to a faulty high pressure pump when the pump is not the problem. Replacing the pump does not fix the problem and results in the trouble code returning.

How serious is the P0848 code?

Failure to repair a P0848 trouble code can result in no apparent problems with the vehicle to a complete failure of the transmission. Other problems vehicle owners can encounter when leaving a P0848 trouble code unfixed include problems shifting, slipping of the transmission, and the transmission becoming overheated.

What repairs can fix the P0848 code?

To repair a P0848 trouble code, the mechanic should perform the following:

Need help with a P0848 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
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

P2159 OBD-II Trouble Code: Vehicle Speed Sensor B Range/Performance
Diagnostic Trouble Code (DTC): P2159 P2159 code definition Vehicle Speed Sensor B Range/Performance...
P2422 OBD-II Trouble Code: Evaporative Emissions Control System (EVAP) Vent Valve Stuck Closed
Diagnostic Trouble Code (DTC): P2422 P2422 code definition Evaporative Emissions Control System (EVAP)...
P0477 OBD-II Trouble Code: Exhaust Pressure Control Valve Low
P0477 code means that the PCM has detected an abnormally low voltage reading often due to the exhaust back pressure control valve circuit.


Related questions

Q: Car stopped randomly and didn't drive afterwards

Hello, thanks for writing in. The computer will go into a failure mode and may not allow the electronic throttle to open if it detects a major computer or sensor fault. There can be many possible failures that will cause...

Q: Does the OBD system use more than lights to communicate with the driver?

Malfunction Indicator Lamps (MIL) and audible alarms are currently the only means by which the On-Board Diagnostics (OBD) system can inform the driver of any issues that adversely affect the operation of the engine or other electronically controlled system. The...

Q: Tranny troubles

You need to have the transmission leak from the bell housing fixed. The fluid leaking is causing the transmission shift problem. The trouble code P2271 indicates that the O2 sensor after the converter shorted rich. This may happen if transmission...