Our check engine light came on awhile back. We took the car to a mechanic who said it was the o2 sensor when he hooked it up to the diagnostic machine. We thought that could wait. A month or two later, we were going on vacation, so we wanted to get it fixed. Took it to the same place, they replaced the o2 sensor. Light went off. About 2/3 of the way on our trip, the light came back on. Took it to a Toyota dealer in Ohio. They came up with the same problem with the o2 sensor saying it was broken. They figured they should check the fuel injectors, that the car was running lean. Three of them were working okay, and they replaced the other three. Check engine light went out. Almost home and the light came on again. Well, we had been hearing this te te te te noise when we first accelerate and that noise started after we got the oil changed in the car before the light came on. The noise is still there. (No, it’s not the AC - it happens when the AC is off.) Every time I accelerate it’s te te te te te. Any clue? So far, we’ve spent about $1350 on repairs that haven’t fixed the problem. The mechanics don’t seem to listen to me when I tell them about the sound, just seem concerned about the diagnostic computer. I think the sound definitely has something to do with it. My husband thinks that it’s a pinhole in the exhaust.
I think you’re using the wrong name. You’re not clueless at all. You’ve spotted a clue that no one else seems to care about. A leak in the exhaust can let in air. Fresh air in the exhaust adds … oxygen, which can throw off the o2 sensor’s signal. An exhaust leak in an 8 year old car would not be unusual.
That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here.
Regarding warning lights:
if the coolant temp light comes on, shut off the engine ASAP
if the oil warning light comes on, shut off the engine ASAP
if a FLASHING MIL/CEL comes on, shut off the engine ASAP
ASAP means driving to the berm of the highway right now and not waiting for the next exit.
But if the MIL/CEL is not flashing, then it’s not an urgent indicator.