i have a 2002 f150 5.4L 4x4 and it is driving me crazy. for over a year now my check engine light will not come on when there is a problem. i have had to replace 3 coil packs and none of them have made the check engine light come on, and now its on seven cylinders again and its a pain in the a$$ trying to figure out problems with it with no engine light. last month the spark plug blew out of the head and the engine light still didn't come on. any body have any ideas why it will not come on? i am sooo close to selling this truck because its such a pain, but i like the way it looks a lot so i'd prefer to keep it. PLEASE help, thanks

 

When you first turn the ignition on (don't start it), does the check engine light light up with the rest of the other lights?

 

yes it does

 

You misunderstand the purpose and function of the MIL.

 

Try checking your TPS. Mine went out and it ran like a 3 legged dog and the light didn't come on. If you do have to replace it save your self some trouble and get the motorcraft brand.

 

Not everything on the engine is monitored. Some components will fail and never set a check engine light. There are certain thresholds that have to be met during a number of drive cycles in order for the check engine light to be illuminated.
Scan your vehicle and see if there are any faults stored. There may not be since the check engine light is not on. Or they may be old ones that havnt been reset.

 

or there could be pending codes that just have not set yet.