Today on the way to work, the check engine light came on. I did the trick of turning on and off the ignition 3 times to have it flash the codes. It appears to be giving me 12,21,55. not sure about the 12, but the 21 is the O2 sensor code. I have a 94 I6 engine. Is there only one sensor? Is there a way to remove it and test it, or do most people just replace them? Also is it just as simple as unscrewing it and screwing a new one back in?


sean

 

If you want to test it you will need a volt meter,back probe it on the sensor side while running,it should read.01-.09 approx. To replace just screw it out and a new one in,unplug it first. Your jeep being a 94 has one sensor prior to the cat/obd-1

 

If it is throwing a code, just replace it. unplug, unscrew,screw and plug. That simple.