The diagnostic code P0490 OBDII refers to a failure in the Exhaust Gas Recirculation (EGR) System. This failure is due to electrical problems.
The EGR system is an integral part of the vehicle’s emission system whose function is to prevent the formation of Nitrogen Oxides in the cylinders. This system is controlled by the Powertrain Control Module (PCM) which directs the EGR valve to open or close as speed, temperature, and load demands to maintain the proper temperature in the cylinder head. To activate this valve, there are 2 wires to an electrical solenoid in the EGR. There is also a potentiometer on the solenoid which signals the position of the EGR pin.
When this code is set, it is because the EGR valve is open, and there is a high voltage in the control circuit. If there is a condition that produces an unexpected high voltage in the circuit, this DTC code is set.