jeep diagnostics????????

[03 USMC 17]

What you are refering to is called flash codes. You cycle the key on and off 3 times...... turn on..turn off...turn on...turn off...turn on and leave on..the check engine light will now begin to flash codes so watch it...count the number of flashes and write the number down for example a flash,flash..pause..flash would mean a code 21.. ...when there are no more codes present the check engine light will flash a 55... example: flash,flash,flash,flash,flash..pause..flash,flash,flash,flash,flash

 

[Drummer forever]

i saw on a youtube video that it was posible to run self diagnotics on my jeep by useing the key and turning it on and off 2 times? do you only do this if the check engine light is on? my jeep is a 1989 comanche