P0847 — Transmission Fluid Pressure Sensor/Switch “B” Circuit Low #

The description for this diagnostic trouble code (DTC) can vary by vehicle manufacturer.

• Transmission Fluid Pressure Sensor/Switch “B” Circuit Low (General/SAE)
• Transmission Oil Pressure Switch “B” Circuit Low (Honda/Acura)
• Auto Trans Fluid Pressure Sensor/Switch B Input Low (Ford/Lincoln)
• Pressure Switch “B” Low Input (GM/Chevrolet)

Summary of Code P0847 #

P0847 indicates that the vehicle’s Engine Control Module (ECM) or Transmission Control Module (TCM) has detected a low electrical signal from the Transmission Fluid Pressure Sensor/Switch “B”. This sensor monitors hydraulic fluid pressures within the automatic transmission to ensure proper shifting and operation. When the sensor reports a voltage lower than the expected range, the system flags this code. The fault can cause shifting issues, warning lights, or even limp mode. Addressing the root cause is important to avoid transmission damage.

Common Symptoms for Code P0847 #

Drivers may notice several symptoms if P0847 is active. These can range from subtle to obvious, depending on the severity and how the transmission responds to the sensor’s signal. If the code is intermittent, symptoms may come and go. Typical signs include:

• Check Engine Light (CEL) or Transmission Warning Light illuminated
• Harsh, delayed, or erratic shifting
• Transmission stuck in one gear (limp mode)
• Reduced fuel economy
• Possible “failsafe” or reduced power mode

Probable Causes for Code P0847 #

Several conditions can trigger this fault code. The most common causes are related to the sensor itself, the wiring, or internal transmission issues. Here are the top reasons based on frequency:

1. Faulty Transmission Fluid Pressure Sensor/Switch “B” (the sensor may be internally shorted or stuck)
2. Open or shorted wiring or connectors (corroded, damaged, or loose connectors in the sensor circuit)
3. Low or dirty transmission fluid (improper fluid level or contamination can affect sensor readings)
4. Internal transmission hydraulic problems (like worn valves, faulty solenoids, or pressure leaks)
5. Failed Transmission Control Module (TCM) or Engine Control Module (ECM) (rare, but possible)

Step-by-Step Diagnosis for Code P0847 #

Accurate diagnosis is essential to avoid replacing unnecessary parts. Here’s a proven step-by-step approach:

1. Record the code and freeze frame data using an OBD-II scanner.
2. Clear the code and road test the vehicle to see if it returns.
3. Inspect the transmission fluid for proper level and contamination (burnt smell, discoloration, debris).
4. Visually inspect wiring and connectors at the sensor for damage, corrosion, or looseness.
5. Test the sensor circuit using a multimeter: check for proper reference voltage, ground, and signal voltage at the sensor connector.
6. Compare live data from the pressure sensor to the expected range (refer to OEM specifications).
7. If all wiring and fluid are OK, test or replace the sensor as needed.
8. If the problem persists, further inspect the transmission’s internal components or the TCM/ECM as a last resort.

Possible Repairs for Code P0847 #

Repairs should always address the root cause to ensure the code does not return. Depending on your diagnosis, typical fixes include:

• Replace the Transmission Fluid Pressure Sensor/Switch “B” if it tests faulty
• Repair or replace damaged wiring/connectors in the sensor’s electrical circuit
• Flush and refill the transmission fluid to the correct level with OEM-specified fluid
• Repair internal transmission issues (such as faulty solenoids or hydraulic leaks)
• Replace or reprogram the TCM/ECM only if proven defective (rare)

Is It Safe to Drive with Code P0847? #

Limited use only. While some vehicles may seem to drive normally, P0847 can lead to poor shifting, limp mode, or even transmission damage if ignored. Driving long distances or under heavy load with this code can cause further issues. It is best to address the problem as soon as possible to avoid expensive repairs.

Vehicles Most Commonly Affected by P0847 #

This code appears most frequently in vehicles equipped with electronically controlled automatic transmissions. It is commonly reported in:

• Nissan/Infiniti (Altima, Rogue, Frontier, Maxima, Murano, Pathfinder, Titan, etc.)
• Honda/Acura (Accord, Odyssey, Pilot, CR-V, Ridgeline, MDX, TL, etc.)
• Chrysler/Dodge/Jeep (Grand Caravan, Pacifica, 300, Ram, etc.)
• Ford/Lincoln (Fusion, Escape, F-150, Explorer, etc.)
• GM/Chevrolet (Silverado, Malibu, Equinox, Traverse, etc.)

Common Mistakes & Best Practices for P0847 #

Misdiagnosis can lead to unnecessary part replacements or ongoing issues. Follow these best practices:

• Do not replace the sensor before checking wiring and fluid condition first.
• Avoid using non-OEM sensors, as aftermarket parts may not perform to the same standards.
• Always verify the transmission fluid level and type—incorrect fluid can cause sensor faults.
• Don’t overlook minor wiring or connector damage; even slight corrosion can trigger this code.
• Compare live sensor data with OEM specs before condemning the sensor or TCM.

Quick FAQ for Code P0847 #

Q: Can I simply clear the code and keep driving?
A: Clearing the code without fixing the root problem will likely result in the code and symptoms returning. It’s best to diagnose and repair the underlying issue.

Q: Will changing the transmission fluid fix P0847?
A: If the problem is caused by low, dirty, or incorrect fluid, a fluid change may resolve the code. However, if the sensor or wiring is faulty, further repairs will be needed.