Heated 02 Sensor

**owheeler** · 04-29-2021, 08:27 AM

What is a fix for a 2001 Trans Am when scanner says heated 02 not ready, rejected at Illinois Inspection Station.? No service engine light.

**sjgreen6** · 05-01-2021, 12:24 PM

Surprised it is not throwing a code but basically you need a new Oxygen sensor. Each of the sensors preheats when you start your car so they can properly read the emissions and adjust your air/fuel ratio. You have 4 of them, two in front of the CATs and two after the CATs. Three are the same part number and one (upstream right) is a different part number due to the length of the wire. Hopefully the inspection station identified which one is not heating up properly. If not ,you need to know before you can change it. If the ones on your car are original or you don't know the history, it is worth it in my opinion to just change them all. Only tool you will need is an Oxygen Sensor socket for your ratchet, some penetrating spray, and a lot of patience. Best to do it on a lift or at least up on jack stands. A couple of them are pretty easy to reach and a couple have other challenges like one that runs the wire over the trans and one that is really close to the frame on the driver's side exhaust manifold. I typically buy this type of part at RockAuto and they are showing Bosch sensors for under $25 each. Dealership will cost you more per sensor but obviously if this is your daily driver that may be a better option.

**owheeler** · 05-02-2021, 01:07 PM

Originally Posted by sjgreen6

Surprised it is not throwing a code but basically you need a new Oxygen sensor. Each of the sensors preheats when you start your car so they can properly read the emissions and adjust your air/fuel ratio. You have 4 of them, two in front of the CATs and two after the CATs. Three are the same part number and one (upstream right) is a different part number due to the length of the wire. Hopefully the inspection station identified which one is not heating up properly. If not ,you need to know before you can change it. If the ones on your car are original or you don't know the history, it is worth it in my opinion to just change them all. Only tool you will need is an Oxygen Sensor socket for your ratchet, some penetrating spray, and a lot of patience. Best to do it on a lift or at least up on jack stands. A couple of them are pretty easy to reach and a couple have other challenges like one that runs the wire over the trans and one that is really close to the frame on the driver's side exhaust manifold. I typically buy this type of part at RockAuto and they are showing Bosch sensors for under $25 each. Dealership will cost you more per sensor but obviously if this is your daily driver that may be a better option.