P0012 is a common trouble code. It affects vehicles with variable valve timing (VVT). The list of VVT vehicles is growing, and the Subaru Impreza can have VVT, and is known to develop this code.
P0012 is generic, which means that it has the same definition for the Impreza as it does on any other vehicle.
VVT changes the frequency and distribution of gases entering and exiting the combustion chamber. It allows the engine to act as though it has different camshaft profiles at different RPM’s.
This ability to alter valve timing is great for both power and fuel economy.
Related: P0011 Subaru Impreza
P0012 Definition Subaru Impreza
The Subaru Impreza utilizes camshaft actuators to change the valve lift depending on the RPM of the motor. This allows for a more efficient cam profile at any speed.
With P0012, the camshaft actuator is leaving the timing retarded.
Camshaft Position Actuators change the lift of the camshaft up to 25 degrees. They are hydraulic, which means that they use the vehicle’s engine oil to control lift. So, if you have low oil pressure or dirty oil, it can keep them from doing their job properly, and trigger P0012.
Subaru Impreza P0012 Symptoms
When the timing is over retarded, it can really cause some issues with the motor. Here are some of the typical symptoms of P0012 in the Subaru Impreza:
- Poor Idle Quality– If the camshaft actuator fails it can be tough for the engine to find the right idle speed or idle smoothly.
- Decreased Gas Mileage– Now the engine can no longer adjust its cam timing on the fly, it will no longer be able to produce optimal combustion, which equals poor economy.
- Lost Power– The Impreza’s engine will not be able to produce as much power. This is because the cam profile will not allow it run a performance power curve when you need more power.
- Service Engine Soon Light– Most of the time, you’ll be able to feel or see one of the above symptoms, but if you can’t, the service engine soon light will still come on and let you know that something is wrong.
- Tough to Start Motor– With the timing over retarded, it is going to be difficult to start the motor, especially when it is warm.
Possible Impreza P0012 Causes
There are quite a few different things that can cause the P0012. Here are the most common causes:
- Engine Timing– If the camshaft(s) are no longer synced to the crank properly (such as if the timing chain jumped a tooth), it can cause the engine timing to be off enough to throw the P0012 even though it’s not the Actuator’s fault. Here’s more on that from this site: Timing Chain Jumped Symptoms and Diagnosis
- Engine Oil– If the engine oil is dirty or low, it may cause the actuator to function improperly. Also, the oil viscosity can be off
- Bad Intake Camshaft Position Actuator Solenoid– The actuator solenoid itself can go bad over time. You certainly don’t want to start here, since a lot of the time it’ll be something else that causes the P0012 to appear.
- Wiring Issues– The wiring going from the solenoid to the ECM can become damaged or broken. This will throw the P0012 OBDII code. The wiring harness to the intake camshaft position sensor may also develop a poor connection. YouTube: How to Find an Open or Short the Fast Easy Way.
- Bad ECM (highly unlikely)- If the Impreza’s computer goes bad, then it may throw this code along with other issues. Here’s how to tell if you have a bad ECM Autoblog: Symptoms of a Bad ECM.
Here’s a phenomenal video on how to test a cam/crank actuator. Make sure that you check everything else that you can before actually opening up an engine.
Conclusion
If it has been an excessive period of time since the last time that you’ve had an oil change, or you find that there may be reason to believe that the oil thickness is wrong, change the oil and see if that helps anything. Good luck diagnosing the P0012 in your Subaru Impreza. If you would like to add anything, please leave a comment below.