When I did spark plug changes about two weeks ago, the passenger bank had oil on all spark plugs. Since there was oil residue around the valve cover and in the spark plugs, I suspected that the gaskets should be replaced.

I took out the gas cap and the fuel pump fuse to relieve fuel pressure in the fuel rail as I had no clearance to take off the valve screw due to the fuel rail blocking it. I started the car to use up the fuel in the fuel lines.

I then proceeded to remove the fuel supply line from the fuel rail. Then I unbolted the valve cover and removed. After cleaning and putting on new valve covrer gasket, I torque to specs and reattached everything.

Put the fuse back and gas cap. I started the car but to my dismay, the check engine light is on and it does not turn off.

What causes the check engine light to turn on and how do I reset?

I am a new Audi A4 owner.

Thanks!

 

You have set an OBD trouble code, probably when you started the car with the fuel pump fuse removed. You can either take to the dealer who will read and clear the code for a fee, or you can find someone with a gauge that will do this. I have a Scan Gauge tool that does this which I use for my '98 Volvo. I don't know if the new A4 I'm waiting for uses OBD2 or some new system for on board diagnostics.

 

Actually the code reinstated itself as the check engine light is no longer on. After several hours, I restarted teh car and the problem resolved.