Not needed, turn the ignition on/off three times then to the on position.
Step one - Have a pen and paper ready
Step two - on, off, on, off, on, off, on
Step three - Your check engine light will begin to flash. Trouble codes are two digit. Code 13 will look like Flash .... Flash,Flash,Flash. Code 21 would look like Flash, Flash ..... Flash etc. Right down the codes.
Step four - When you get a code 55 it means end of code sequence. Search the forum or google for "jeep trouble code listing" for your year.
Step five - Post back on the forum with any questions.