P0847
UniversalTransmission Fluid Pressure Sensor/Switch B Circuit Low
Medium SeverityThis code indicates that the vehicle's computer has detected a voltage reading that is too low from the Transmission Fluid Pressure Sensor/Switch B circuit. This typically means there's an electrical issue with the sensor or its wiring, or the transmission fluid pressure itself is abnormally low, which can lead to erratic shifting or the transmission entering a limp mode.
⚠️ Before You Begin (Safety First)
Always ensure the vehicle is safely supported on jack stands and the engine is off before working underneath. Disconnect the battery to prevent electrical shock. Transmission fluid can be hot; allow the vehicle to cool before inspecting or working on the transmission.
Common Symptoms
- Check Engine Light illuminated
- Harsh or erratic shifting
- Delayed gear engagement
- Transmission stuck in limp mode (e.g., stuck in 3rd gear)
- Reduced fuel economy
- Transmission slipping
Common Causes
- Faulty Transmission Fluid Pressure Sensor/Switch B
- Wiring harness open or short circuit to the sensor
- Corroded or loose electrical connectors for the sensor
- Low transmission fluid level
- Clogged transmission fluid filter
- Internal transmission mechanical issue (e.g., failing transmission pump or valve body)
- Faulty Transmission Control Module (TCM), though less common
Frequently reported on: Ford F-Series (2000-2015), Chevrolet Silverado (2000-2015), Chrysler Town & Country (2008-2016), Honda Odyssey (2005-2010), General/Universal Automatic Transmission Vehicles
Diagnostic Steps
- Check transmission fluid level and condition, adding fluid if necessary according to manufacturer specifications.
- Visually inspect the wiring harness and electrical connectors for the Transmission Fluid Pressure Sensor B for any obvious damage, fraying, corrosion, or loose connections. Repair as needed.
- Clear the code with an OBD-II scanner and test drive the vehicle to see if the code returns.
- If accessible, use a multimeter to test the resistance or voltage signal from the sensor according to your vehicle's service manual specifications to confirm sensor failure.
- If other issues are ruled out, consider replacing the Transmission Fluid Pressure Sensor/Switch B. This may require draining transmission fluid and removing the transmission pan.
👨🔧 When to Call a Professional
If after checking the wiring and fluid levels, the code persists and transmission performance worsens significantly, contact a professional mechanic immediately to diagnose potential internal transmission issues or complex electrical problems.
Commonly Asked Questions
Can I drive with a P0847 code?
It's not recommended. While your vehicle might still drive, transmission performance can be significantly impaired, potentially causing further internal damage if not addressed promptly. It's best to diagnose and repair the issue as soon as possible.
Where is the Transmission Fluid Pressure Sensor B located?
Its exact location varies significantly by vehicle make and model. It is typically found on or inside the transmission valve body or transmission housing. Consulting your vehicle's specific service manual or a repair guide is essential for the precise location.
Is replacing the Transmission Fluid Pressure Sensor difficult?
The difficulty can range from moderate to advanced. Access to the sensor often requires draining transmission fluid and removing the transmission pan or other transmission components, which can be messy and require specific tools and torque specifications for reassembly.
What's the difference between a transmission fluid pressure sensor and a switch in this context?
A transmission fluid pressure sensor provides a variable voltage signal that corresponds to the actual fluid pressure, allowing the TCM to monitor pressure across a range. A switch, conversely, typically provides an on/off signal when a specific pressure threshold is met or exceeded. For diagnostic purposes of a 'circuit low' fault, the troubleshooting steps are often similar.
Can low transmission fluid cause the P0847 code?
Yes, severely low transmission fluid can lead to insufficient pressure within the transmission. While the code specifically refers to a circuit low, inadequate pressure can sometimes trigger sensor readings that mimic a circuit problem or highlight an underlying issue related to fluid pressure, which the sensor then reports.