o2 sensor question
 

Are the o2 sensors the same for both up and downstream or do they differ?

When I bought mine from rockauto they had some designated for up and some for down,

I would assume that since the up is before the cat and down is right after, there is probably a difference in them.

their is a difference. The one closer to the engine is the upstream sensor. the one behind the cat towards the rear of the vehicle (really it's in the middle) is the downstream. the connectors are different as well. i believe the bung size is the same for both though

Standard size bung but the US and DS sensors are slightly different. On 2000+ models with 4 O2 sensors the two US and DS sensors have different wiring.

NTK is the OEM by the way. Very cheap on Rock Auto.

Like the other guys said upstream and down stream are different sensors . I sell Denso O2 sensors and never had any problems as far as fit or function . i had to replace both on my 98 . just make sure when you buy them get OE style not the PITA universal ones

The upstream O2S will have a longer pigtail than the downstream O2S, and the holes in the probe differ. The downstream probe will have mutiple slotted holes and the upstream will have only four round holes.

Google 'NTK Oxygen Sensors' and you should be able to fined the NTK/NGK site which will give you the NTK O2S part numbers for your application.

is there a reason behind the question ? is your CEL on ?

I have an extra o2 that goes after that cat and was checking if it works at the downpipe