The BMW Diagnostic Trouble Code (DTC) P1315 corresponds to a "Misfire Cylinder 2 With Fuel Cut-Off" condition. Here's what it typically means:
**P1315 - Misfire Cylinder 2 With Fuel Cut-Off**
This DTC indicates that the engine control module (ECM) has detected a misfire in Cylinder 2 and has cut off fuel to that cylinder as a safety measure. A misfire occurs when the air-fuel mixture in the cylinder does not ignite or burns irregularly, resulting in a loss of power and increased emissions.
Common causes of a P1315 code in a BMW include:
1. **Ignition System Issues:** Problems with the ignition system, such as a faulty spark plug, ignition coil, or spark plug wire in Cylinder 2, can lead to misfires.
2. **Fuel Delivery Issues:** Issues with fuel delivery to Cylinder 2, such as a clogged fuel injector, low fuel pressure, or a malfunctioning fuel pump, can cause misfires.
3. **Air Intake Problems:** Air intake restrictions or leaks can affect the air-fuel mixture and lead to misfires.
4. **Vacuum Leaks:** Vacuum leaks in the intake system can introduce excess air into Cylinder 2, affecting the air-fuel mixture.
5. **Sensor Problems:** Malfunctions in sensors like the Mass Airflow Sensor (MAF) or the Oxygen Sensor can lead to incorrect data and misfires.
To diagnose and address a P1315 code, a qualified technician typically performs the following steps:
1. **Visual Inspection:** Inspect the ignition system components, including the spark plug, ignition coil, and spark plug wire in Cylinder 2, for damage or wear.
2. **Check Fuel Delivery:** Verify fuel pressure and inspect the fuel injector for clogs or other issues in Cylinder 2.
3. **Inspect Air Intake:** Check the air intake system for restrictions or leaks that may affect the air-fuel mixture.
4. **Check for Vacuum Leaks:** Perform a smoke test or use a propane torch to check for vacuum leaks in the intake system.
5. **Data Monitoring:** Use a diagnostic scan tool to monitor live data, including sensor readings, to help identify the source of the misfire.
