A bad oxygen sensor could be the cause of a check engine light. You can replace the sensor yourself in your own car. You will be able to save money with diy.
First you must locate the bad oxygen sensor. You can have your car diagnosed at Auto Zone for free which will specify which sensor out of four sensors. The 1993-2004 Jeep Grand Cherokee 4.0L engines have four oxygen sensors. Two located upstream and two located downstream. See attached diagram. 2 upstream (referred to as 1/1 and 2/1) and 2 downstream (referred to as 1/2 and 2/2). With this emission package, the rear/upper upstream sensor (2/1) is located in the exhaust downpipe just before the rear mini-catalytic convertor. The front/upper upstream sensor (1/1) is located in the exhaust downpipe just before the front mini-catalytic convertor. The rear/lower downstream sensor (2/2) is located in the exhaust downpipe just after the rear mini-catalytic convertor, and before the main catalytic convertor. The front/lower downstream sensor (1/2) is located in the exhaust downpipe just after the front mini-catalytic convertor, and before the main catalytic convertor.
Second you must purchase your oxygen sensor either from a local automotive parts store or online. I recommend BOSCH oxygen sensors. All four oxygen sensors located in the Jeep Grand Cherokee are different prices and sizes. While you are purchasing your oxygen sensor, ask the store clerk or look online for an oxygen sensor socket. It has a split down the middle for the cable to fit.
Third, use the picture above for specific location on the oxygen sensor you need to replace. Use the socket to remove the bad oxygen sensor and replace it with the new one.
