What sensor is located in the exhaust manifold?

 

That would be your front oxygen sensor.

 

I purchased two O2 sensors. One downstream which fit by the catalytic converter (Denso 234-4450). One upstream which I hoped would fit at the exhaust manifold (Denso 234-4734). It would not mate up connecter wise. Rock Auto shows another (Denso 234-9150) upstream sensor with correct connector alignment tabs. Would this be the correct sensor. Very confusing looking at parts suppliers as to what I need. Why all the options?

 

Just to let anyone know that runs into the same problem-Yes the Denso 234-9150 is the correct sensor. It is an air-fuel ratio sensor.

 

This will be the one and only Volvo we will ever own. We bought this car brand new and have had nothing but problems with this car. Top of motor rebuilt at 40000 by Volvo because it was consuming oil (sixty thousand miles later eating oil-not leaking-same as before). Two power steering pumps, two fuel pumps, ignition switch, trunk release, alternator, battery discharging overnight, and the normal maintenance things like front and rear hubs. All we were trying to save in gas went to repairs and then some.

 

Ouch, sometimes you get a lemon. Maybe a lease vehicle would be better?