What Does the P0391 Code Mean?
OBD-II Code P0391 is defined as a Camshaft Position Sensor “B” Circuit Range/Performance. The Camshaft Position Sensor measures the exact rotational position of the camshaft, providing critical data signals used by the engine control module (PCM) to control the fuel injectors and ignition coils. When the PCM detects an irregular signal or no signal, it sets code P0391.
What Causes the P0391 Code?
The P0391 code can be triggered by several issues, including:
- Broken tone ring
- Camshaft Position Sensor (CMP) failure
- Powertrain Control Module (PCM) failure
- Wiring issues
What Are the Symptoms of the P0391 Code?
Drivers may experience various symptoms when their vehicle triggers the P0391 code, such as:
- Decreased engine performance
- Engine may not start
- Increased fuel consumption
How Serious Is the P0391 Code?
The P0391 code is classified as urgent, indicating that immediate action is necessary. This code represents significant malfunctions that can lead to severe damage to the vehicle or pose safety risks to the driver and passengers.
How to Diagnose the P0391 Code
To accurately diagnose the P0391 code, follow these steps:
- Use an OBD-II scanner to confirm the presence of the P0391 code.
- Inspect the Camshaft Position Sensor and its wiring for damage or disconnection.
- Check the tone ring for breaks or misalignment.
- Test the PCM to ensure it is functioning correctly.
- Clear the code and test drive the vehicle to see if the code returns.
Common Repairs for the P0391 Code
Repairs commonly needed for the P0391 code may include:
- Replacing the Camshaft Position Sensor
- Repairing or replacing damaged wiring
- Replacing the broken tone ring
- Replacing the Powertrain Control Module (if faulty)
How Much Does It Cost to Fix the P0391 Code?
The cost to fix the P0391 code can vary widely depending on the specific issue and labor rates in your area. On average, you might expect to pay anywhere from $100 to $400 for repairs, depending on whether you need a simple sensor replacement or more extensive electrical work.
Can I Fix the P0391 Code Myself?
While some vehicle owners may feel comfortable diagnosing and replacing the Camshaft Position Sensor themselves, it’s essential to have a clear understanding of the problem and the necessary steps for proper repair. If you’re unsure about performing these tasks, it is advisable to seek professional assistance to avoid further complications.
