The engine code P1512 indicates a fault with the intake manifold switchover valve, also known as the Intake Manifold Runner Control (IMRC) system
. The specific meaning can vary by vehicle manufacturer, but it generally refers to an issue with the valve staying closed when it should be open. What the switchover valve does
Many modern engines use a variable geometry intake manifold with a switchover valve to change the airflow into the combustion chambers. This design uses long runners at low RPM for increased torque and shorter runners at high RPM for more horsepower. A malfunctioning valve can disrupt this process.
Common causes
- Sticking or clogged valve: One of the most frequent causes is carbon buildup on the shutter valves, which causes them to stick and not operate correctly.
- Faulty actuator or motor: The valve is typically controlled by an electronic actuator or a vacuum-actuated motor. A failure in this component can prevent the switchover valve from opening or closing.
- Vacuum leaks: If the system is vacuum-operated, a leak in the vacuum lines or hoses can cause the valve to fail.
- Wiring issues: A damaged or corroded wiring harness or a loose electrical connector can prevent the engine control module (ECM) from sending the correct signals to the actuator.
- ECM malfunction: In rare cases, a faulty ECM can be the cause, but this is usually ruled out after other components are checked.
Common symptoms
- Poor acceleration: A stuck valve can cause a significant loss of engine power, especially during acceleration.
- Reduced engine power warning: On some vehicles, a "Reduced Engine Power" message may appear, putting the engine into a fail-safe mode.
- Erratic or high idle: If the valve sticks, it can cause an unstable idle that may surge or stall.
- Check Engine Light (CEL): The P1512 code will be stored and the CEL will illuminate.
- Engine hesitation or stalling: The vehicle may hesitate or stall intermittently, especially when coming to a stop or after driving for a long time.
How to diagnose and fix the problem
- Check for vacuum leaks: Inspect all vacuum lines and fittings around the intake manifold for cracks or loose connections.
- Inspect and clean the valve: Check the intake manifold runner control valve for carbon buildup. If it's sticking, cleaning it with a suitable intake cleaner may resolve the issue.
- Test the actuator and solenoid: Use a scan tool to command the actuator or solenoid to operate and listen for it to move. If it doesn't move or makes strange noises, it may be faulty. You can also test the electrical circuits with a multimeter.
- Check the wiring and connectors: Look for any frayed or damaged wires and corroded pins at the connector leading to the actuator.
- Replace the component: If the actuator or solenoid is confirmed to be faulty, it may need to be replaced. Some manufacturers, such as Dorman, offer replacement parts for just the valve or actuator, which can be less expensive than replacing the entire manifold.
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