Service Engine Soon Light

[lush99svt]

That damn light keeps coming on after about a week everytime I disconnect the battery. It started happening after MOD (90 JL MAF&filter). Truck is running great! Is it that 5.0 volt crap? Do I need to install the chip?


Can the MAF & filter stay on when i go to the dealer or will they give me a hard time? :m

 

[Don's Bolt]

If you put a 90 MM Mass Air on a 99 Lightning without a chip it will set off the Service Engine Soon Light. You do need a chip programed for the 90 Mass Air. Your truck is running leaner than stock thats why the light is going on.