Quick Answer
P0391 means: P0391 indicates a fault in the camshaft position sensor 'B' circuit, affecting engine performance.
Can I drive with P0391? Immediate attention is recommended to prevent engine damage.
Common Questions
What does P0391 mean and how does it affect my car?
The P0391 code signifies that there's a problem with the camshaft position sensor 'B' circuit. This sensor is vital for your engine's timing and performance. If this issue is not resolved quickly, it can lead to poor engine performance, increased fuel consumption, and may even cause the engine to stall, compromising safety.
What are the most common causes of P0391 and how much does it cost to fix?
Common causes include a faulty camshaft position sensor, wiring issues, or timing problems. Repair costs typically range from $150 to $300 for sensor replacement, while wiring repairs may cost between $50 and $150.
Can I drive my car with P0391 or should I stop immediately?
It is not advisable to drive your vehicle with the P0391 code. Doing so can lead to severe engine problems and safety risks. It's best to have the issue diagnosed and repaired as soon as possible.
How can I diagnose P0391 myself using GeekOBD APP?
To diagnose P0391 with the GeekOBD APP, start by scanning for error codes. Review the freeze frame data to understand the conditions under which the code was triggered. Use the app’s diagnostic tools to perform live data checks on the camshaft position sensor's performance.
What vehicles are most commonly affected by P0391?
Common vehicles affected by P0391 include the 2011-2016 Ford F-150, 2013-2018 Honda Accord, and various models from Nissan and Chevrolet, particularly those with V6 and V8 engines.
How can I prevent P0391 from happening again?
Regular maintenance, including timely oil changes and inspection of the timing belt, can help prevent P0391. Additionally, keeping the engine clean and ensuring all wiring is intact can reduce the risk of sensor failures.
What is P0391?
The diagnostic trouble code (DTC) P0391 indicates a problem with the camshaft position sensor 'B' circuit range or performance. This sensor is crucial for monitoring the position of the camshaft relative to the crankshaft in your vehicle. It helps the Engine Control Module (ECM) manage the timing of fuel injection and ignition. A failure in this circuit can lead to poor engine performance, increased emissions, and even damage to the engine over time. Commonly found in vehicles like the 2011-2016 Ford F-150 and 2013-2018 Honda Accord, this code can trigger the check engine light and may cause the engine to run poorly or stall. Symptoms may include rough idling, difficulty starting, and reduced acceleration. It’s important to address this issue promptly, as neglecting it can lead to more serious engine problems. In essence, the P0391 code signifies that the ECM is not receiving accurate data from the camshaft position sensor, which can disrupt the overall engine operation.
System: P - Powertrain (Engine, Transmission, Emissions)
Symptoms
Common symptoms when P0391 is present:
- The check engine light illuminates consistently, indicating an underlying issue that needs attention.
- Drivers may experience engine hesitation during acceleration, making it difficult to merge or maintain speed.
- Fuel economy can drop by 10-15%, leading to more frequent trips to the gas station.
- Rough idling can occur, causing the vehicle to shake or vibrate when stopped.
- In some cases, the engine may stall unexpectedly, posing a safety risk while driving.
Possible Causes
Most common causes of P0391 (ordered by frequency):
- The most common cause of P0391 is a faulty camshaft position sensor, with a likelihood of around 60%. A failing sensor often results from wear and tear or exposure to heat.
- Another frequent cause is wiring or connector issues, such as damaged wires or loose connections, which can hinder signal transmission and lead to performance problems.
- In some cases, an improperly timed engine can trigger the P0391 code. Regular maintenance and timing belt inspections can help prevent this.
- Less common but serious causes include internal engine problems like a jumped timing chain or belt, which can severely affect engine operation.
- A rare cause might be a malfunctioning Engine Control Module (ECM), which can misinterpret sensor data and lead to erroneous codes.
P0391 Repair Costs
Cost Breakdown by Repair Type
Camshaft Position Sensor Replacement
Replacing a faulty camshaft position sensor is a common solution for P0391.
- Total: $150 - $300
- Success rate: 85%
Wiring Repair
Repairing damaged wiring or connectors can resolve the issue if the sensor is functioning properly.
- Total: $50 - $150
- Success rate: 70%
Money-Saving Tips for P0391
- Start with the most common and least expensive repairs first
- Use GeekOBD APP to confirm diagnosis before replacing expensive parts
- Consider preventive maintenance to avoid future occurrences
- Compare prices for OEM vs aftermarket parts based on your needs
- Address the issue promptly to prevent more expensive secondary damage
Diagnostic Steps
Professional P0391 Diagnosis Process
Follow these systematic steps to accurately diagnose P0391. Each step builds on the previous one to ensure accurate diagnosis.
Step 1: Step 1: Initial visual inspection - Check for obvious signs like damaged wiring, loose connections, or corrosion, which may take about 5-10 minutes
Step 1: Initial visual inspection - Check for obvious signs like damaged wiring, loose connections, or corrosion, which may take about 5-10 minutes.
Step 2: Step 2: OBD2 scan with GeekOBD APP - Use the app to retrieve all codes and freeze frame data, helping to understand the fault context in around 10-15 minutes
Step 2: OBD2 scan with GeekOBD APP - Use the app to retrieve all codes and freeze frame data, helping to understand the fault context in around 10-15 minutes.
Step 3: Step 3: Component testing - Employ a multimeter or specific diagnostic tools to test the camshaft position sensor and related components, which can take about 20-30 minutes
Step 3: Component testing - Employ a multimeter or specific diagnostic tools to test the camshaft position sensor and related components, which can take about 20-30 minutes.
Step 4: Step 4: System function test - After repairs, verify the proper operation of the sensor and clear any codes, usually around 10-15 minutes
Step 4: System function test - After repairs, verify the proper operation of the sensor and clear any codes, usually around 10-15 minutes.
Step 5: Step 5: Road test verification - Drive the vehicle under various conditions to confirm the success of the repair, which may take 15-20 minutes
Step 5: Road test verification - Drive the vehicle under various conditions to confirm the success of the repair, which may take 15-20 minutes.
Important Notes
- Always verify the repair with GeekOBD APP after completing diagnostic steps
- Clear codes and test drive to ensure the problem is resolved
- Address underlying causes to prevent code recurrence
Real Repair Case Studies
Case Study 1: Camshaft Sensor Replacement in a 2015 Ford F-150
Vehicle: 2015 Ford F-150, 75,000 miles
Problem: The customer reported a persistent check engine light and poor acceleration.
Diagnosis: Using the GeekOBD APP, we retrieved the P0391 code and confirmed the camshaft position sensor was faulty after testing.
Solution: Replaced the camshaft position sensor and cleared the codes.
Cost: $250 (sensor cost: $200, labor: $50)
Result: The vehicle's performance improved significantly, and the check engine light remained off.
Case Study 2: Wiring Repair in a 2014 Honda Accord
Vehicle: 2014 Honda Accord, 60,000 miles
Problem: The vehicle exhibited rough idling and stalling intermittently.
Diagnosis: After scanning for codes, P0391 was found. Inspection revealed damaged wiring to the camshaft position sensor.
Solution: Repaired the damaged wiring and ensured all connections were secure.
Cost: $100 (labor cost: $50, materials: $50)
Result: The car ran smoothly post-repair, with no further issues reported.