P0847 Code: Here's How to Solve It Fast

The P0847 trouble code is a diagnostic trouble code (DTC) that signals an issue with the transmission fluid pressure sensor or switch "B" circuit in your vehicle's automatic transmission system. This code is set when the Powertrain Control Module (PCM) detects that the voltage from the sensor does not match the expected values. Understanding this code is crucial for vehicle owners and DIY mechanics, as it can lead to significant transmission issues if not addressed promptly.

P0847 Code Meaning	P0847 Code Common Causes
Transmission Fluid Pressure Sensor/Switch "B" Circuit Low	Faulty Transmission Fluid Pressure Sensor
Electrical circuit malfunction in the sensor	Corroded or damaged wiring and connectors
Incorrect fluid levels or quality	Faulty Powertrain Control Module (PCM)
Internal transmission mechanical issues	Low transmission fluid levels
Hydraulic blockages in the transmission system	Faulty electronic pressure control solenoid

Symptoms of P0847 Code

When the P0847 code is triggered, drivers may experience several symptoms, including:

• Malfunction Indicator Light (MIL): The check engine light on your dashboard will illuminate.
• Change in Shift Quality: You might notice rough or erratic shifting while driving.
• Limp Mode Activation: The vehicle may start off in second or third gear to protect the transmission.
• Reduced Fuel Economy: Poor transmission performance can lead to decreased fuel efficiency.
• Transmission Slipping: You may feel the transmission slipping out of gear unexpectedly.

Technical Explanation of P0847 Code

The P0847 code specifically relates to the "B" circuit of the Transmission Fluid Pressure Sensor (TFPS). The TFPS sends critical information about fluid pressure to the PCM, which uses this data to manage shifting and torque converter lockup. If the voltage signal from this sensor falls below a predetermined threshold, the PCM will trigger the P0847 code.

The "B" circuit refers to a specific part of the overall fluid pressure monitoring system. Problems in this circuit can arise from various sources, such as faulty sensors, wiring issues, or even internal mechanical failures within the transmission itself.

Step-by-Step Diagnosis of P0847 Code

Diagnosing and resolving a P0847 code involves several steps:

1. Initial Inspection:

• Check for any additional trouble codes using an OBD-II scanner.
• Inspect transmission fluid levels and quality; ensure it is clean and at appropriate levels.

1. Visual Inspection:

• Examine wiring and connectors related to the TFPS for signs of damage, corrosion, or loose connections.
• Clean any corroded terminals with electrical contact cleaner.

1. Voltage Testing:

• With the key in the ON position (engine off), use a digital voltmeter to measure voltage at the TFPS connector.
• The reading should match manufacturer specifications (typically 5V or 12V). If it does not, repair or replace wiring as necessary.

1. Resistance Testing:

• Disconnect the TFPS and measure resistance across its terminals using an ohmmeter.
• Compare readings with manufacturer specifications; if they are outside acceptable ranges, replace the sensor.

1. Check PCM Functionality:

• If all tests pass but the code persists, consider that a faulty PCM may be at fault. This requires professional diagnostics and potential reprogramming after replacement.

Solution Methods for P0847 Code

To resolve a P0847 code effectively, consider these solutions:

• Replace Faulty Sensors: If testing indicates a defective TFPS, replace it with a new one.
• Repair Wiring Issues: Address any damaged wiring or corroded connectors to ensure proper electrical flow.
• Fluid Maintenance: If fluid levels are low or dirty, perform a fluid change and ensure proper levels are maintained.
• Electronic Component Repairs: Replace any malfunctioning electronic pressure control solenoids or other related components.
• Professional Help: If you are unable to diagnose or resolve the issue yourself, seek assistance from a qualified mechanic who can perform advanced diagnostics.

Cost Estimates

The costs associated with diagnosing and repairing a P0847 code can vary significantly based on location and vehicle type:

• Diagnostic Fee: Expect to pay between $75 to $150 for a professional diagnostic service.
• Sensor Replacement: A new TFPS typically costs between $50 to $200 depending on make and model.
• Wiring Repairs: Simple repairs may cost around $100, while extensive rewiring could exceed $300.
• Fluid Change: Transmission fluid changes can range from $100 to $250 depending on labor rates and fluid type used.

Warnings and Recommendations

• Do Not Ignore Warning Lights: Ignoring the check engine light associated with a P0847 code can lead to more severe transmission damage over time.
• Follow Manufacturer Guidelines: Always refer to your vehicle’s service manual for specific diagnostic procedures and specifications related to your make and model.
• Avoid DIY Repairs Without Knowledge: If you are not confident in your ability to diagnose or repair automotive issues, consult a professional mechanic. Attempting complex repairs without proper knowledge can lead to further damage or safety risks.

Frequently Asked Questions About P0847

• What does P0847 mean?
  The P0847 code indicates that there is an issue with the Transmission Fluid Pressure Sensor/Switch "B" Circuit Low.
• Can I drive my car with a P0847 code?
  While it may be drivable, continuing to drive can lead to poor transmission performance and potential damage.
• How do I reset the P0847 code?
  You can reset it by clearing codes with an OBD-II scanner after addressing any underlying issues.
• What could cause a false P0847 reading?
  A temporary electrical glitch or intermittent wiring issue could trigger a false reading.
• Is replacing the TFPS always necessary for a P0847?
  No, it’s essential first to diagnose whether it’s truly defective before replacement.
• How often should I check my transmission fluid?
  It's generally recommended to check your transmission fluid every 30,000 miles or as specified in your owner's manual.
• What are common mistakes when diagnosing P0847?
  Overlooking wiring issues or assuming it's solely a sensor problem without thorough testing.
• Should I use OEM parts for repairs?
  Using OEM parts is often recommended for reliability and compatibility with your vehicle.

In conclusion, understanding and addressing the P0847 trouble code is vital for maintaining your vehicle's performance. By following systematic diagnostic procedures and addressing underlying issues promptly, you can prevent further complications and ensure safe driving conditions. Always consider seeking professional assistance if you encounter difficulties during diagnosis or repair.