This way you can sit and listen to the radio without everything else draining.
Check engine light doesnt come on with key on.
There is 2 key modes on the switch.
Radio on mode only allows you to use the radio.
I doubt any of the things mentioned have any affect on the check engine light.
Do not check resistances.
The light bulb for cel has a power feed with 12 volts runing to it with key on all the times.
A loose fuel cap is one of the most common reasons why the check engine light turns on.
Ok it looks like fuse 7 in the dash fuse box supplies power to the check engine warning light.
The same power feed in the cluster powers up the seatbelt light abs and a couple others.
It then goes to the electronic control module.
It notably prevents gasoline fumes from leaving.
This is called the self test mode for the computer.
The cap is a crucial part of a car s fuel delivery system.
Here is the deal run jumper wire at diagnostic connection but instead of first 2 slots go with 1 and 4 if check engine light comes on its the circuit board in module under dash its about 2 inches wide 4 inches long either lite green or gray or black plastic tube box with a door on one end will be tape up alongside wiring cut tape open lid and there is a small circuit board that handles lie and codes from computer.
Since you said the other lights work then.
If the check engine light doesn t come on in the run position it means the computer failed the self test mode and there s a problem with the computer.
When turning the ignition switch to the run position the check engine light should come on.