So I leave the DMV 30 minutes ago and they want a smog check. OK car runs good no worries and as I'm driving away I get my first Service Engine with the code pc0153 - Is that Murphy's Law in action or what?

I searched archives and it looks like the left O2 sensor, is that correct?

How many sensors are there? and where are they located? Are there 4 - one infront and behind the cat? Does anyone have the OEM part number - I'll order it today if I can find the part number.

I've got a bunch of front end stuff coming from GMpartsdirect: stabilizer bar links and 2 stabilizer bushings and 4 front control arm bushings (total cost $180). If I could get the O2 sensor I could have my mechanic throw it on while he has the car up.

Thanks and enjoy the weekend :thumbsup: , Maclean

The year and engine would help.
P0153 - Heated Oxygen Sensor (HO2S) Slow Response Bank 2 Sensor 1
If this is the code you got I assume it is a Northstar. It has 4 sensors.
Bank 2 Sensor 1 = right bank (firewall) manifold
Bank 2 Sensor 2 = pre-cat
Bank 2 Sensor 3 = aft-cat
Bank 1 Sensor 1 = left bank (front) manifold

Thanks Ranger !

Sorry it's a 1996 STS.

Where exactly is the firewall manifold. I've read this is the hard one to replace - actualy it was one of your old posts.

How do I know which one to purchase from Rockauto or Gmpartsdirect since there are 4.

Thanks, Maclean

By "firewall manifold" I meant the right bank exhaust manifold on the firewall side of the engine. Yes, that is the hardest on to get at. Remove the strut tower cross brace if you have one. That will give you more room to work. Have you looked at either of the two sites? I would assume they have a way of differentiating the sensors. I think the two manifold sensors are the same and the two cat sensors are the same. I think you also need a special O2 sensor socket.