P0847: How to Diagnose & Fix — Transmission Fluid Pressure Sensor/Switch 'B' Circuit Low
2 vehicles · 2 makes · $150-$4,500 repair
How to diagnose and fix P0847: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Acura RDX · 2007–2012
The 2007-2012 RDX's 5-speed automatic uses clutch pressure switches to confirm hydraulic apply of the 2nd and 3rd clutch packs. These switches are a recurring failure point on the first-generation car — the 3rd clutch switch most often. When one fails or its circuit shorts, the TCM sets P0847/P0848 and flags P0700 at the PCM, illuminating the check engine light and frequently the D light. The car may drop into a fail-safe gear pattern with harsh or limited shifting. This is an electrical/sensor failure, not internal clutch damage, and is regularly misquoted by shops as a transmission rebuild.
Common Symptoms
- Check engine light with P0700
- D indicator light blinking
- Harsh or limited shifting / fail-safe gear
- Loss of some forward gears
- No other driveability symptoms when cold
How to Fix
Scan the TCM (not just generic P0700) to identify which clutch pressure switch circuit is faulted. Inspect the connector and harness for oil wicking and corrosion first — a contaminated connector reproduces the same code. Replace the failed 2nd or 3rd clutch pressure switch (a screw-in switch on the transmission case) and change the fluid with genuine Honda ATF DW-1; do not substitute generic ATF, which degrades shift quality on this unit. No recall or warranty extension covers this.
Sources for this issue (2)
Subaru Outback · 2010–2015
Early Lineartronic CVT Outbacks (2010-2015) have documented internal CVT failures — most commonly valve-body faults, but also chain/pulley and pressure-control problems — that can cause harsh or delayed engagement, RPM flare, jerking, limp mode, or complete loss of drive. Subaru acknowledged the problem with a CVT Warranty Extension to 10 years / 100,000 miles covering the CVT and everything associated with it (valve bodies, internal parts, harnesses, and leaks) on 2010-2015 Legacy/Outback (and related models). A revised/upgraded valve body is installed at repair. This is separate from the low-speed torque-converter shudder complaint; here the transmission can set fault codes and go into failsafe. Out of warranty, a full CVT replacement is a multi-thousand-dollar repair.
Common Symptoms
- Harsh or delayed engagement into gear
- RPM flare / slipping under acceleration
- Jerking or shuddering
- Transmission warning light / limp mode
- Whining or loss of drive
How to Fix
If you experience harsh/delayed engagement, flaring, jerking, or a transmission warning, scan for CVT codes and get it evaluated quickly. First verify the vehicle is within (or was serviced under) the 10-year/100,000-mile CVT Warranty Extension — if so the valve-body or CVT repair should be free; escalate to Subaru of America if a dealer initially denies coverage, since owners report success on valve-body claims. Keep CVT fluid at the correct level/spec and address any leaks promptly, as low pressure accelerates valve-body wear. Out of warranty, a rebuilt/updated valve body is far cheaper than a complete CVT unit — get a diagnosis of the specific failed component before authorizing a full replacement.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Subaru 31706AA331 CVT Control Valve Body
early CVT valve body only after TCM diagnosis proves the valve-body fault Fitment/availability: 2010-2012 Outback 2.5-liter EJ253 CVT branch; confirm VIN and production date Fitment/availability: ships in 1-2 business days with Add to Ca…
- Genuine Subaru 31825AA055 CVT Control Valve Kit
later 2.5-liter CVT valve body only after TCM diagnosis proves the fault Fitment/availability: 2013-2015 Outback 2.5-liter FB25 CVT branch; current supersession of 31825AA050-054, confirm VIN Fitment/availability: Add to Cart live when r…
- Genuine Subaru 31706AA144 High-Torque CVT Control Valve Body
2015 3.6R high-torque CVT valve body after exact diagnosis and VIN selection Fitment/availability: 2015 Outback 3.6R CVT branch within this card; current supersession of production-specific 31706AA140/141, confirm VIN Fitment/availabilit…
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Sources for this issue (3)
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P0847 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0847 mean?
P0847 stands for "Transmission Fluid Pressure Sensor/Switch 'B' Circuit Low." The transmission fluid pressure sensor/switch 'B' circuit voltage is below the expected range (too low / shorted to ground).
What are the most common causes of P0847?
The most common causes of P0847 are: Sensor signal shorted to ground, Faulty pressure sensor/switch B, Corroded/damaged connector, Internal TCM fault. The specific cause varies by vehicle.
How much does it cost to fix P0847?
Repair costs for P0847 range from $150 to $4,500, depending on the vehicle and root cause.
Which vehicles are affected by P0847?
Au7o has documented P0847 across 2 vehicle models from 2 manufacturers: Acura, Subaru.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.