Variable valve timing (VVT) systems aren’t only used to increase performance.
Variable valve timing (VVT) benefit to fuel consumption and emission are slowly leaving the (EGR) valve in the past.
In theory, maximum overlap is needed between intake valves and exhaust valves’ opening whenever the engine is running at high speed. However, when the car is running at medium speed in highway, in other words, the engine is running at light load, maximum overlapping may be useful as a mean to reduce fuel consumption and emission.
Since the exhaust valves do not close until the intake valves have been open for a while, some of the exhaust gases are recirculated back into the cylinder at the same time as the new fuel / air mix is injected.
As part of the fuel / air mix is replaced by exhaust gases, less fuel is needed.
Because the exhaust gas comprise of mostly non-combustible gas, such as CO2, the engine runs properly at the leaner fuel / air mixture without failing to combust.
As great as variable valve timing (VVT) is, it is also vulnerable to some problems.
On VVT systems that use oil pressure to actuate the cam phaser, oil quality, viscosity and contamination problems can affect the operation of the phaser.
If the phaser does not receive adequate oil pressure, or the oil is the wrong viscosity (too thick or too thin), or the oil is dirty, it may prevent the phaser from working properly.
This, in turn, can hurt engine performance, fuel economy and emissions. Such faults will often turn on the Check Engine light and set a VVT-related fault code.
Variable valve timing (VVT) Generic OBD II Fault Codes:
- P0010….A Camshaft Position Actuator Circuit Bank 1
- P0011….A Camshaft Position Timing Over-advanced or System Fault Bank 1
- P0012….A Camshaft Position Timing Over-retarded Bank 1
- P0013….B Camshaft Position Actuator Circuit Bank 1
- P0014….B Camshaft Position Timing Over-Advanced or System Fault Bank 1
- P0015….B Camshaft Position Timing Over-Retarded Bank 1
- P0020….A Camshaft Position Actuator Circuit Bank 2
- P0021….A Camshaft Position Timing Over-Advanced or System Fault Bank 2
- P0022….A Camshaft Position Timing Over-Retarded Bank 2
- P0023….B Camshaft Position Actuator Circuit Bank 2
- P0024….B Camshaft Position Timing Over-Advanced or System Fault Bank 2
- P0025….B Camshaft Position Timing Over-Retarded Bank 2
How do I reset the “Check Engine or Service Engine Soon” Light?
After you’ve properly diagnosed and fixed the problem that triggered the OBD trouble code, you can reset or clear the Check Engine a number of different ways:
- You can just drive it and after a certain number of driving cycles it will just clear by itself.
- Disconnect your battery, turn on the headlight switch for about five to ten minutes, and re-connect the battery. This is pretty simple, but will likely result in you losing your radio presets and perhaps some other small things like that.
- Most if not all scan tools have an option to clear or reset codes without the use of any tools or touching the battery.