The light can be cleared by fixing the original malfunction, disconnecting the battery, or resetting the on-board diagnostic, or OBD, system with a scanner. It is important to ascertain the cause of the light before clearing it.
A check engine light could indicate a catastrophic problem in the Jeep’s engine, or it may be something as simple as a loose gas cap. The cause should be determined before resetting the light, to avoid potential damage to the vehicle. One option is to take the Jeep to a professional mechanic, who will not only clear the check engine light, but also diagnose and repair the cause of the error.
A home mechanic can clear the code with an OBD scanner. Available at any auto supply store, an OBD scanner plugs into the OBD port on the vehicle and reads any error codes the engine has detected. In Jeep Grand Cherokees, the port is usually found under the steering wheel, near the driver’s side door. After reading the code and diagnosing and fixing the problem, the user can select an option on the scanner to clear all diagnostic codes, which should reset the check engine light.
A "hard reset" is another option. This involves disconnecting the battery and draining all power from the car’s electrical system by running the lights. This deprives the OBD system of current, erasing its memory. However, if the original issue has not been addressed, the check engine light will simply turn on again soon after power is restored.