The P0847 trouble code is a diagnostic trouble code (DTC) that indicates an issue with the transmission fluid pressure sensor/switch “B” circuit, specifically signaling that the circuit is low. This code is part of the OBD-II system, which monitors various components of a vehicle’s performance, including the transmission system. When the powertrain control module (PCM) detects a discrepancy between the desired and actual fluid pressure levels in the transmission, it triggers the P0847 code. 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 | Malfunctioning electronic pressure control solenoid |
| Indicates a problem with fluid pressure regulation in the transmission | Faulty transmission fluid pressure sensor |
| Potential for decreased shifting performance or limp mode operation | Low or contaminated transmission fluid |
| May cause check engine light to illuminate | Internal mechanical issues within the transmission |
| Bad hydraulic pump or faulty powertrain control module (PCM) | |
| Electrical issues such as damaged wiring or corroded connectors |
Symptoms of P0847 Code
Understanding the symptoms associated with the P0847 code can help you identify issues early and take appropriate action:
- Malfunction Indicator Light (MIL): The check engine light may illuminate on your dashboard.
- Change in Shift Quality: You may experience rough or erratic shifting, indicating that the transmission is not operating optimally.
- Limp Mode Activation: The vehicle may start in 2nd or 3rd gear to protect the transmission from damage, limiting your driving capabilities.
- Transmission Slippage: There may be instances where the transmission slips out of gear unexpectedly.
Technical Explanation
The P0847 code relates to the transmission fluid pressure sensor/switch “B” circuit. This sensor is critical for monitoring and regulating hydraulic pressure within the transmission system. The PCM relies on accurate readings from this sensor to ensure proper shifting and overall performance of the vehicle’s automatic transmission.
When there is a malfunction in this circuit, it can lead to improper fluid pressure levels, which in turn affects shifting quality and can cause further damage to the transmission if not addressed. The “B” designation refers to a specific area of the fluid pressure circuit rather than an individual component.
Step-by-Step Diagnosis
Diagnosing a P0847 code involves several steps:
- Initial Scan: Use an OBD-II scanner to confirm that P0847 is present and check for any additional codes that may provide more context.
- Visual Inspection: Inspect wiring and connectors associated with the transmission fluid pressure sensor for signs of damage, corrosion, or loose connections.
- Check Fluid Levels: Ensure that the transmission fluid is at the correct level and free from contamination.
- Sensor Testing:
- Disconnect the electrical connector from the transmission fluid pressure sensor.
- Using a digital voltmeter (DVM), measure voltage at the sensor connector while turning on the ignition (engine off). Compare this reading with manufacturer specifications.
- If voltage readings are incorrect, trace wiring back to find shorts or breaks.
- Manual Pressure Test: If electrical tests are inconclusive, perform a manual hydraulic pressure test using a gauge connected to the transmission system.
- Check for Internal Issues: If all external components are functioning correctly but issues persist, internal mechanical problems within the transmission may need to be investigated.
Solution Methods
To resolve a P0847 trouble code, follow these potential solutions based on your diagnosis:
- Repair or Replace Electrical Components: If damaged wiring or connectors are found during inspection, repair or replace them as necessary.
- Sensor Replacement: If tests indicate that the transmission fluid pressure sensor is faulty, replace it with a new one.
- Fluid Change: If contamination is detected in the transmission fluid, perform a complete fluid change and ensure proper levels are maintained.
- Solenoid Replacement: If electronic pressure control solenoids are malfunctioning, they should be replaced to restore proper function.
- Hydraulic Pump Replacement: In cases where low hydraulic pressure persists despite other repairs, consider replacing the hydraulic pump.
- Professional Assistance: If internal mechanical issues are suspected or if troubleshooting becomes too complex, seek help from a certified automotive technician.
Cost Estimates
The cost of diagnosing and repairing a P0847 trouble code can vary significantly based on several factors:
- Diagnostic Fees: Expect to pay between $100 to $150 for diagnostic services at most repair shops.
- Parts Costs:
- Transmission Fluid Pressure Sensor: $50 – $200
- Electronic Pressure Control Solenoid: $100 – $300
- Hydraulic Pump Replacement: $300 – $800
- Labor Costs: Typically ranges from $75 to $150 per hour depending on location and shop rates.
Overall repair costs can range from as low as $150 for minor electrical repairs to over $1,000 for extensive mechanical work involving internal transmission repairs.
Warnings and Recommendations
- Do Not Ignore Warning Lights: Ignoring a check engine light associated with P0847 can lead to more severe transmission problems down the line.
- Use OEM Parts When Possible: For replacements, using original equipment manufacturer (OEM) parts ensures compatibility and reliability.
- Regular Maintenance: Regularly check and change your vehicle’s transmission fluid according to manufacturer recommendations to prevent future issues.
- Seek Professional Help When Needed: If you are unsure about any step in diagnosing or repairing this issue, consult with a trained automotive technician.
Frequently Asked Questions About P0847
- What does P0847 mean?
P0847 indicates that there is a problem with the transmission fluid pressure sensor/switch “B” circuit being low. - What causes P0847?
This code can be caused by faulty sensors, low or contaminated transmission fluid, damaged wiring, or internal mechanical issues. - Can I drive my car with a P0847 code?
While you might be able to drive short distances, it’s advisable to address this issue promptly to avoid potential damage. - How do I fix a P0847 code?
Fixing this code typically involves inspecting electrical connections, replacing faulty sensors, ensuring proper fluid levels, and addressing any internal mechanical issues. - Will clearing codes fix my problem?
No, clearing codes will not fix underlying issues; it only resets the check engine light. - How serious is a P0847 code?
P0847 can lead to significant transmission problems if left unaddressed; it’s important to diagnose and repair promptly. - What tools do I need to diagnose P0847?
You will need an OBD-II scanner, digital volt/ohmmeter, manual pressure gauge, and possibly manufacturer-specific wiring diagrams. - Should I consult a professional mechanic?
If you’re not comfortable diagnosing or repairing this issue yourself, it’s best to seek help from an experienced automotive technician.
In conclusion, understanding and addressing the P0847 trouble code is essential for maintaining your vehicle’s performance and longevity. By following proper diagnostic procedures and solutions outlined above, vehicle owners and DIY mechanics can effectively manage this issue before it escalates into more serious problems. Regular maintenance and prompt attention to warning signs will help ensure your vehicle operates smoothly for years to come.