if the check engine light came on a code was stored in the ECM
to read them:
With the ignition off, switch the key on, off, on, off, on.
Make sure you don't actually start your Jeep, turn the ignition to the ON position, but do not turn it so far that you start cranking the engine.
The check engine light will start to flash, count these flashes. Each code is a two digit number, for example 23 would be FLASH FLASH <pause> FLASH FLASH FLASH <long pause>