P0848
PowertrainTransmission Fluid Pressure Sensor / Switch "B" Circuit High
You'll usually notice this one as a gearbox that's gone clumsy. The shifts feel harsh, maybe a thump going into third, and on a bad day the car drops into limp mode and won't pull out of second or third. Behind all that, the powertrain control module is seeing a higher voltage than it expects from the transmission fluid pressure sensor 'B' circuit. That high reading is nearly always electrical, either the sensor itself or the wiring feeding it, though low or filthy fluid can throw the readings out too.
ⓘ Information only. This page provides general educational information about fault code P0848. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P0848 mean?
P0848 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Transmission Fluid Pressure Sensor / Switch "B" Circuit High.
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Engine warning light on, sometimes with the D indicator flashing on Honda and Acura models
- • Harsh or jerky gear changes, often most obvious around the change into third
- • Gearbox dropping into limp mode, starting off in second or third and refusing to shift up
- • Delayed engagement when you select Drive or Reverse, or the odd slip mid-shift
- • A definite slam or judder during shifts that wasn't there before
- • Fuel economy creeping worse because the box isn't shifting cleanly
Possible causes
Causes commonly associated with P0848, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Faulty pressure sensor or switch, often the 3rd clutch pressure switch on Honda and Acura autos. This is the usual offender
- 2. Corroded or loose connector at the sensor, water and road salt get into these plugs and cause exactly this high-voltage reading
- 3. A short to power in the signal wire, which pins the voltage high all the time
- 4. Low, dirty or burnt automatic transmission fluid affecting the pressure the sensor reads
- 5. A failed electronic pressure control solenoid in the valve body
- 6. A blockage in the hydraulic circuit or valve body so the actual pressure is wrong
- 7. Internal gearbox wear shedding debris, which is the worst-case and least common cause
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Get a scanner on it and pull every code, not just P0848. Misfire or other transmission codes alongside it change the whole picture, and you want to see what came first
- 2. Check the fluid before touching anything electrical. Pull the dipstick or check the level by spec, look at the colour and have a smell. Dark or burnt fluid points at internal trouble, not just a sensor
- 3. Find the pressure sensor (commonly on the valve body or gearbox casing) and inspect the connector and pins for green corrosion, spread terminals or a loose lock. This is where most P0848 faults actually live
- 4. Back-probe the sensor connector with a multimeter, key on engine off, and confirm the reference voltage matches spec, typically 5V on most setups. A reading sitting high here points straight at wiring or a short to power
- 5. Wiggle-test the harness and connector while watching live data. A reading that jumps when you flex the loom tells you it's the wiring rather than the sensor
- 6. If the wiring and fluid check out and the code keeps coming back, get a manual pressure gauge on it or hand it to a transmission specialist for a valve-body inspection
Common questions about P0848
What's this likely to cost me to sort out? +
Depends entirely on which cause it is. If it's a dirty connector or low fluid, you're looking at very little, a bottle of the correct ATF and some contact cleaner. Replacing the pressure sensor or switch is the common job and runs roughly £120 to £300 fitted at an independent, more like £350 to £500 at a main dealer because of their hourly rates and OEM parts pricing. If it turns out to be a solenoid or valve-body work, that's into the high hundreds, and at that point get a couple of quotes from gearbox specialists before agreeing to anything.
How do I tell whether it's the sensor, the wiring or the gearbox itself? +
The fluid tells you a lot quickly. Clean, red and full-level fluid points you at electrics. Burnt-smelling dark fluid means look harder at the box. After that it's the connector: a high-voltage code that clears or changes when you wiggle the loom is wiring, plain and simple. If the voltage at the connector sits high with everything looking clean and tight, suspect the sensor. Only when fluid, wiring and sensor all test fine do you start worrying about internal pressure or solenoid faults, and that's a job for a pressure gauge and a specialist.
Can I have a go at this myself? +
The cheap end of it, yes. Topping up or changing the fluid with the correct spec, and cleaning out a corroded connector with electrical cleaner and a smear of dielectric grease, fixes a fair share of these and costs almost nothing. Swapping the pressure sensor is doable if you can reach it, though some are awkwardly placed on the valve body and you'll want the torque figure and the right replacement part. Once you're into solenoids or anything inside the gearbox, leave it to a garage with the gear to test hydraulic pressure properly.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →