Check Engine Light Doesnt Come On With Key On

Radio on and full systems on.

Check engine light doesnt come on with key on.

A loose fuel cap is one of the most common reasons why the check engine light turns on. This way you can sit and listen to the radio without everything else draining. Radio on mode only allows you to use the radio. 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. It notably prevents gasoline fumes from leaving. 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.

This unit is a solid state unit. The light bulb for cel has a power feed with 12 volts runing to it with key on all the times. 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. Do not check resistances.

There is 2 key modes on the switch. It then goes to the electronic control module. This is called the self test mode for the computer. I doubt any of the things mentioned have any affect on the check engine light.