I have a 2005 PT Cruiser. The check engine light came on for the back 02 sensor. I replaced it. Then the check engine light comes on again. This time the code says the 02 sensor for the front. So, I replaced it. Everything fine for a day again. Check engine light comes on again, says the same 02 sensors are amiss. I've already replaced both with Bosch 02 sensors but the codes keep telling me the 02 sensors are bad. I've been told the cat is bad or is just dirty. Don't know if that's true, so I tried some cataclean. Nothing. Guess what else? Now the oil light comes on when it's cold. It didn't do that before. Now the door ajar light comes on intermittently while I'm driving. So I have to stop and open and shut all the doors and it doesn't come again. Do I have a possessed computer that's setting off the codes? I'm not sure where to go from here. Any suggestions?
Thank you so much for the response. The engine oil light only comes on when it's cold, when I start the car again after turning it off when it's it warmer, the light is off. I've checked the oil and it isn't using any at all. I'll try the knocking technique. Let you know what happens. By OEM do you mean to purchase from the dealer? The Bosch say they're OEM but maybe not. Any ideas why the open door light comes on while I'm driving? It's intermittent, and I think it only does it when it's cold also. This is a very weird car. Granted it's not the best car on the market, but it's all I have and if I can figure this stuff out without having to spend a lot, the better. I appreciate your advice.
It looks like NTK makes the OEM sensors for your car: https://shop.advanceautoparts.com/p/ntk-oe-type-oxygen-sensor-23159/20501945-P?utm_medium=ymme&vehicleIdSearch=399425&isAllVehicle=false
Also on the door light, you probably just have a loose latch and it is tripping the sensor. I would make sure the strike plate on the door frame is tight. This is the little metal "hoop" that is screwed into place that the door latch catches on to. Check to make sure it isn't really loose.
Sounds like you have an unhappy PT there.
The easiest way to tell if a catalytic converter is bad is to go under the car and knock on it. MAKE SURE THE CAR IS COLD FIRST. DO NOT TOUCH AFTER THE ENGINE HAS BEEN RUNNING. They get extremely hot fast, so maybe in the morning before you leave for the day or some time like that.
Anyway, knock it pretty good. If you hear rattling like marbles in a can, it means it has failed internally and needs to be replaced.
A question I would like to ask is have you noticed it burning any oil? If so, you want to address that first as oil will ruin a converter and also foul out 02 sensors. I ask because you had a low oil light, so just curious of you had checked the oil level.
Many times it can be that you just need to use OEM 02 sensors. Your car may not like the Bosch ones.
