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.
The reasons why the DTC code P0490 OBD2 is configured are the following:
Electrical connections may be poor due to bad connectors.
Perhaps there are blockages in the EGR System solenoid or it may be damaged.
Possible solutions of the DTC code P0490 Generic
What you should do when solving the error code P0490 OBDII is:
If the engine starts but the idle speed is erratic, unplug the electrical connector from the EGR valve while the engine is running. If the idle speed shows no change, the valve pin is stuck in the open position. You must remove the EGR valve and check it for carbon build-up. Change the valve if necessary.
If you lose power at idle when the connector is removed, there may be a short in the positive battery circuit that keeps the valve open.
Inspects all related vacuum lines for damage. Also, make sure that the vacuum actuators and check valves are working properly. Replace any vacuum lines that are not in good condition.