My Corolla 2006 had the engine light come up, and the code PO 171. I changed the mass air flow sensor, and a mechanic tried to change the oxygen sensor but he told me that it was welded to the the manifold. (This must have happened years ago after I took the car to a mechanic for repairs after an accident.) I know it's not supposed to be that way, but here is my question: When I park the car on an incline, nose down, overnight for a couple of days, the light comes up. When I park the car on an incline the opposite way, tail down, the light disappears after 2 nights, and stays that way unless the car is either nose down again for a while, or leans to the right side for at least a few minutes at a light. The engine light also disappeared after he tried to detach the oxygen sensor from the manifold (to replace it with a new one) and banged on it a few times, but it came back after I hit a bump on the road. I asked a repair shop to check if anything was loose, they said everything looks fine, and it would have nothing to do with the oxygen sensor anyway, but that's thinking of the way a regular oxygen sensor is attached, not when it's glued to the manifold. Any suggestion please? I know there is a risk detaching the oxygen sensor from the manifold, as the manifold might break, but I wonder if the problem has anything to do with the sensor detaching itself either from the manifold or from the exhaust system. (knocking on the sensor had the light disappear)
Can someone also tell me if a Corolla 2006 has one or two oxygen sensors please? I thought it only had one, but the last shop told me it has two.
Thank you very much.