I replaced the downstream O2 bank1 a while ago with one I bought on ebay.. I looked back on my records for the info because I just found the same number Denso on Amazon listed as a upstream A/F sensor..

The ebay I bought
Brand: DENSO
Part Number: 234-4951
Item Condition: New
Item Description: Oxygen Sensor
Manufacturer Brand Description: OE Style Oxygen Sensor
Quantity Needed: 2;
Position: Downstream

And here is the add from Amazon..

 

According to the Denso catalogue, the Air/Fuel ratio sensor part no is 234-9125.I just checked the amazon link and if you read the description the part offered is an oxygen sensor.
If you go to www.densoautoparts.com you can check the part no yourself.

 

Thanks very much

 

In my experience, neither Amazon's nor eBay's compatibility charts are totally reliable. The only real way I've found to determine the correct part # for my '01 & '03 S-Types is to use the Jaguar Electronic Parts Catalog (JEPC), which is a free download from this forum. It's the same parts catalog used by the Parts Dept at my local Jag dealership, and it lists retail prices the dealership might charge you for your part - a great baseline price for comparison shopping.

Unfortunately, some of the info in the downloadable JEPC is outdated, as many of the listed part numbers have been superseded by newer numbers. By trial and error, I've learned to:

1) obtain the original part # in JEPC (knowing the last 6 characters of your VIN is essential), then
2) cross-reference it thru one of the online genuine Jaguar parts retailers to obtain the latest part number.

If JEPC's part # is outdated, the online search will show the current number for the part. Moreover, a diagram of the part's location - which appears to be straight out of the JEPC -is usually available to ensure you've got the correct part. Some of the online genuine Jag parts retailers are affiliated with a brick and mortar auto dealership.

Once you've determined the most current part number, you can easily search Amazon, eBay, RockAuto.com etc. with confidence by simply searching the part #.

Here's the genuine Jag parts online retailer I use to obtain the most up-to-date part numbers. I've bought a few parts from them and found them to be very helpful and reasonably priced, but not the cheapest place for parts. I am not affiliated with them in any way, so feel free to find your own. If you find a better one (there are several online), please let me know:

Genuine Jaguar OEM Factory Parts sold at Wholesale Prices | GaudinJaguarParts.com

 

Thanks for all that.. Gaudin's prices on O2 sensors are over $260 and cats are around $1000. I did save the site to favorites to verify part numbers as you said.

 

I was not suggesting you buy from Gaudin, but they do give you a baseline price you can use for comparison shopping. I bought all 4 Denso heated sensors for my '03 S-Type 3.0 from TrueBlueParts on eBay -$86 each for upstream, $49 for downstream. These were the lowest prices I could find using the search technique I described in previous post.