All O2 sensors all threaded into the exhaust system at various points.
if you have the 2.2 liter ecotec engine, they are located right on top of the engine, they are located under the top black piece that says ecotec on it.
This sounds like your wheel hubs need replaced. These are where the sensors for ABS and Traction control are located. I'm very surprised a dealer would not be able to find this. It is possible another sensor is bad, but this is the same problem I had with my 2001 Alero. If you have service engine light on, trac. off light and the ABS light on the same time, you may be able to get it fixed my reprogramming the power control module (with updated software calibration). Mine was fixed for free at a dealer under a recall campaign when GM called me yesterday.
Larger engine, Nitrous injection, Turbo, Supercharger, rebuild the engine with higher compression, modified cam... It just takes money and time. A really big hill.
Inside the floor shift console. Should have an access panel on the right side of console that can be removed to gain access to ECM.
It is part of the fuel pump module inside the fuel tank. I think the only answer is to replace the entire unit.
There are two o2 sensors on this car.
I have a 2000 olds alero 4 clylinder and yes it has two oxygen sensors!! I have a 2000 olds alero 4 clylinder and yes it has two oxygen sensors!!
Yes a bad senser in any vehicle will turn your engine light on. Even a performance air intake will turn your engine light on.
By the battery.
The thermostat is located on a 2003 Oldsmobile Alero in the thermostat housing. The thermostat housing is located on the rear side of the engine block.
The O2 senors will be in the exhaust system. They may be in the exhaust manifold all the way to the convertor. You can locate them easily. They will be the only thing in the pipe or manifold that have wires attached to them.
In the engine oil pan.
If it is a V6, it is located in front between engine and the cooling fans.
Follow the upper radiator hose to the engine. It should be located in a housing near where the hose connects to the engine.
In the 2000 Alero, it is fuse 34 in the engine fuse box, which is located near the battery. You can check the same fuse for the 1999 Alero and see if that is it.
Usually in a removable housing at the engine end of the upper radiator hose
on the right side of the engine block.