Jeep Cherokee O2 Sensor Light

My Cherokee (4 wheel drive with the 4.0 liter I-6 and 105,000 miles) has a continuous problem with the O2 sensors. Years ago, the wiring was damaged on the rear sensor after my wife?s Labrador tried to eat it (tripping the check engine light). I beat the dog, replaced that sensor and reset the light. Months later, the check engine light came on again with an O2 code for the front sensor. I replaced the sensor and reset the light again. Months later I got another O2 code for the back sensor again. Thinking that I may have originally bought a bad sensor, I replaced that sensor and, months later, the check engine light came on again indicating an O2 sensor.

Since then, I?ve looked for other problems that may be causing this. I replaced the intake/exhaust gasket thinking that it may have been sucking in cold air and causing the problem. I checked the fuel pressure and ignition; both appear to be in good condition. I recently replaced both sensors with new Bosch units and reset the light. It stayed out for a day and returned. Also, throughout this time, the truck will stumble at low rpm’s?usually after running and sitting for a few hours. It sounds like it is backfiring through the air intake when it does this. If I push the gas more, the truck accelerates fine and the stumbling goes away. Any ideas about what could be causing this? The truck has a slightly larger, aftermarket catalytic converter and a freer flowing muffler. I?ve tried to rule this out because the truck ran fine for nearly a year after installing this. It all started with the damaged wiring.

Please help me get this truck running right or I will set it on fire and push it off a cliff.

The car is upset that you beat the dog.
If you apologize to the dog, and take the car to a shop to have the O2 sensor wiring checked, the car might forgive you, and stop having issues in the future.

The problem could be from a related part of the fueling system, like the Mass Air Flow Sensor.
If its getting lazy in its old age, it might not be sending a proper signal to the ecu, that then sends too little fuel while the engine is idling.

You might want to have that examined.


Find someone who knows how to troubleshoot with a multimeter and oscilloscope.
Someone who can look at the signals coming from the O2 sensors and make a few resistance/continuity checks.