P0847 moderate

Transmission Fluid Pressure Sensor/Switch B Circuit Low

The P0847 code means the vehicle's onboard diagnostic system has detected: Transmission Fluid Pressure Sensor/Switch B Circuit Low. This is a moderate severity code.

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Keep driving?: Short distances only
DIY difficulty: hard
Estimated cost: $100 - $500 (parts and labor)

Check Your Fluid First

ANCEL AD310 OBD-II Scanner

Read and clear transmission codes. Many trans codes are caused by low or burnt fluid -- check level and color before assuming the worst.

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Read Transmission Codes

LAUNCH CRP123X (Reads All Systems)

Basic scanners only read engine codes. This reads transmission, ABS, and airbag too.

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Common Symptoms

Check Engine Light illuminated
Transmission slipping or flaring between gears
Soft or delayed shifts
Possible limp mode activation

Probable Causes (Ranked by Likelihood)

Short to ground in pressure sensor B signal wire Very High
Faulty pressure sensor B producing low voltage High
Corroded connector at sensor B Moderate
Very low transmission fluid level Moderate

Step-by-Step Diagnostic Procedure

Check transmission fluid level first
Measure voltage at pressure sensor B connector
Test for a short to ground in the signal wire
Replace sensor B if wiring and fluid level are verified good

Frequently Asked Questions

Should I check the fluid before replacing the sensor?

Absolutely. Low fluid is a common cause of low pressure sensor readings and is much cheaper to fix than replacing a sensor.

Can a transmission cooler leak cause P0847?

Yes, a leak in the transmission cooler or its lines can gradually lower fluid level and reduce pressure, triggering a low pressure sensor code.

Is sensor B located in the same area as sensor A?

They are typically both on the transmission case or valve body, but at different locations monitoring different circuits. Refer to your vehicle service manual for exact locations.