01 Ford vs Toyota: Two Completely Different Definitions of Rel… • 02 10 Abbreviations for Sensors Used in Cars • 03 Lean vs. Rich: Which Engine Problem Should You Worry About … • 04 The Simple Under Hood Device That Makes Your Vehicle Guzzle… • 05 This Simple Shortcut Many Drivers Take Often Ends In Engine… • 06 Understanding the 4-Pin Relay: Functions, Applications, and… • 07 MAF vs. MAP Sensors: Unraveling the Key Differences • 08 Experts Warn Ignoring A Weak Ignition Coil Could Leave Your… • 09 The SR-71 Blackbird: Flying at Mach 3.3, what do pilots fee… • 10 Common Car Part Issues and How to Fix Them •

DTC codes / P08xx · Transmission / P0848

P0848Transmission Fluid Pressure Sensor/Switch 'B' Circuit High

P0848 indicates that the transmission control module (TCM) has detected an abnormally high voltage on the signal circuit for transmission fluid pressure sensor or switch 'B'. This sensor monitors hydraulic pressure inside the transmission, and a high voltage reading typically means the circuit is open, shorted to power, or the sensor's internal resistance has shifted out of range.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaTransmission

Symptoms you may notice

  • Illumination of the check engine light or transmission warning light, often with no other noticeable symptoms
  • Harsh or delayed gear shifts, particularly when the transmission is cold
  • The transmission may enter limp mode, limiting operation to a single gear or a reduced set of gears
  • Slipping between gears or a flare during upshifts
  • In some cases, the vehicle may refuse to shift out of park or may shudder during acceleration

Common causes, most likely first

  1. Faulty transmission fluid pressure sensor or switch 'B' itself, with an internal open circuit or resistance drift
  2. Damaged or corroded wiring harness connector at the sensor, causing an open circuit or high resistance
  3. Chafed, broken, or shorted signal wire between the sensor and the TCM
  4. Poor electrical connection at the TCM connector, including bent pins or corrosion
  5. Low transmission fluid level or degraded fluid causing abnormal pressure readings that the sensor reports as high voltage
  6. A stuck or faulty pressure regulator valve that creates actual high pressure, leading the sensor to signal a high voltage condition

How to diagnose and fix it

  1. Verify transmission fluid level and condition; top off or service fluid if it is low or burnt-smelling
  2. Inspect the sensor 'B' electrical connector for corrosion, loose pins, or damaged wiring, and repair as needed
  3. Backprobe the sensor signal circuit at the TCM and compare voltage with the manufacturer's specification to confirm a high-voltage condition
  4. Check the sensor's resistance or voltage output with a multimeter and compare to the factory range; replace the sensor if it is out of specification
  5. Perform a continuity and short-to-power test on the signal wire between the sensor and TCM to rule out harness faults
  6. If the harness and sensor test good, inspect the valve body and pressure regulator for sticking or debris that could cause genuine high pressure
  7. Clear the code and perform a relearn or adaptation drive cycle as required by the manufacturer, then verify the code does not return

What a high voltage reading really means

  • A high voltage on a pressure sensor circuit almost always indicates an open circuit or a sensor with increased internal resistance, not necessarily a failed transmission; many technicians replace the transmission when the fault is a chafed wire.
  • The sensor 'B' designation can refer to a second pressure sensor in some transmissions, often used for clutch or line pressure monitoring, so consult the factory service information for the exact location and function on the vehicle being tested.
  • Transmission fluid pressure sensors are frequently misdiagnosed when the actual problem is a corroded connector pin that creates intermittent high resistance, especially in areas with road salt exposure.
  • A low fluid level or a clogged transmission filter can cause pressure fluctuations that the sensor interprets as a high-voltage signal, so always check fluid condition before condemning electrical parts.
  • On some vehicles, a faulty pressure sensor can set P0848 without ever illuminating the check engine light, storing only a pending code that is discovered during a scan for another issue.

Can I keep driving with P0848?

It is generally safe to drive the vehicle short distances to a repair shop, but avoid heavy acceleration, towing, or sustained highway speeds because the transmission may enter limp mode or shift unpredictably. If the vehicle is already in limp mode or shifting harshly, arrange a tow to prevent further transmission damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage