- Dirty Oil
- Low engine oil level
- Valve Timing Control (VTC) open or shorted circuit.
- Valve Timing Control (VTC) electrical connector
- Faulty Valve Timing Control (VTC)
- Damaged ECM

- Engine Light ON (or Service Engine Soon Warning Light)
- Lack/Loss of power
- Engine rough idle

The Engine Control Module (ECM) optimizes the valve timing using the Valve Timing Control (VTC). The ECM sends a target duty cycle control signal to the VTC. This control signal regulates the oil pressure supplied to the VTC. The VTC can advance or retard the engine timing.