Hey ,
been working on replacing the o2 sensors , now
i know that the downstream sensors should be around
'12 ohms' resistance level between the 2 black wire pins
​​​​​​But when I checked the Upstream one I have seen
'0.3 ohms' resistance level between 2 black wire pins on the sensor itself to be precise
I mean maybe it's ok for the Upstream does anyone knows the exact ohms it should carry ?

## Jaguar S type 3L v6 2006 base##


​​

Careful. Depends on your car model but most use wideband with heaters so depends how hot they are. They are current-sensed so be sure you know what you're doing.

Why are you doing anything like that? OBD solves it better and far easier!

​​​​​Hey ,
Car model ​​​​​​is S type 3L v6 2006
​​​​​​I need to replace the downstream sensor as a code appeared for o2 sensor 2 bank 2 heater control .
When I checked it's resistance it had 0 ohms should be around 12 ,
now when I checked the the o2 sensor 1 on the left bank thats the pre cat had only 0.3 ohms ,
Don't know if it's good , is there any writings about the correct numbers ?

I do not think you can test the heated o2 sensors in this way.
From what I understand they are basicaly a mini generator and they only work when they get hot at about 600 degrees or higher!
The richer the mixture the higher the voltage they produce, up to about 0.9 volts. (0.45 volt is about correct for the correct mixture.)
But please note that I am not an expert about this so I may be wrong?

However, even the jaguar workshop manual only list checking the car wiring to the sensor for shorts or open circuits, not testing the actual sensor itself.
If there is a faulty sensor code and all the wires are ok then it states change the sensor.

Mellow

Your upstreams are linear aka wideband - sensed via current.

If you have no code for them, then stop fussing with them.

Change the one with the code. If you're very unlucky that won't be a fix but 99% it will be.

Make SURE you use a proper one or expect grief.

Those the ones I got for replecmemt (link below) , connection does fit for the
​​​​Upstream not the downstream they both a 4 wire ones



So how do I know if they wideband or narrowband they don't state it , and I already got them .

Rockauto lists these sensors for your model year.
The downstream ones all have a black connector as far as I know.
You may have gotten an upstream sensor from Amazon.

https://www.rockauto.com/en/catalog/...2)+sensor,5132

Denso is supposed to be OEM
Amazon lists this one as downstream:

Denso 234-4951

https://www.amazon.com/Denso-234-4951-Oxygen-Sensor-Ratio/dp/B001F7CFVO/ref=sr_1_5?_encoding=UTF8&c=ts&dchild=1&keywords=A utomotive+Replacement+Oxygen+Sensors&qid=162518322 7&s=automotive&sr=1-5&ts_id=15730891&vehicle=2006-20-93-20--1-6-7-21716--1-1-549--6&vehicleName=2006+Jaguar+S-Type

​​​​​​Yes , thanks allot .

What is the actual code that was generated? It should be a 5 digit code, starting with a letter followed by four numbers, such as P0057. It's very important to go by the code, and not the definition your scanner may provide. Some generic definitions are different than the official Jaguar definition. Codes for your car will be here:

http://www.jagrepair.com/images/Auto..._OBD_II_R2.pdf


I gave P0057 as an example, as that Jaguar definition matches what you said. Careful, because it appears the conversation has gotten a little sidetracked with extra details of how an O2 sensor works. Each sensor has two isolated circuits inside. One circuit is the actual sensor, with two wires providing data to the computer about the oxygen content of the exhaust stream. The other circuit, totally isolated from the first, is the heater circuit with its own two wires. The actual sensor portion, in the first circuit, needs to be toasty hot to operate properly. This second circuit takes care of the heating duties. If indeed you have a P0057 code, the computer is saying the heater circuit is on the fritz for that particular sensor. It's not faulting the totally separate sensor circuit, just the heater function. For the purposes of this discussion, you don't even have to know how the sensor portion works.

Now, if it's still bugging you to understand the details, a sensor itself can be either wide-band or narrow-band. Either type still uses a separate heater circuit. But the big difference between wide and narrow band? Price! Wide-band sensors provide more accurate data over a wider range, hence the name. The only downside is the expense. Narrow band sensors are more limited in range, but are much less expensive. On 2003+ models, wide band sensors are used upstream to take advantage of their better capabilities for engine control. The downstream sensors primarily monitor how well the catalytic converters are working, a much simpler function, and don't need that expensive extra capability. Narrow band sensors are fine in this location. But remember, none of this really matters if dealing with a fault in the heater circuit for a particular sensor.

As far as checking the existing sensor, you can compare the other downstream sensor's heater circuit. (Forget about the two upstream sensors, as I have no idea if their heater circuits are similar to downstream.) Of the four wires on each downstream sensor, only two are for the heater circuit. The color code is immaterial between the actual sensor body and the connector. That's whatever color the sensor manufacturer chose to use. It's not even listed in the wiring diagrams. On the vehicle harness? Yep, that's color coded. But not on the pigtail between the connector and sensor body.

Wiring diagrams are here:

http://www.jagrepair.com/images/Auto...cal-2006on.pdf

See figure 03.1 for your engine. The four sensors are at the upper left corner. Note how each sensor has four wires. The left two wires (labeled -3 and -4) are the sensor circuit, which doesn't matter for the moment. The right two wires (-1 and -2) are the heater circuit. Look carefully on the plug and you may find some tiny numbers. If not, you can check the wire colors on the vehicle harness. I highly suspect if you compare the left and right downstream sensors, you find no continuity on bank 2, the one throwing the code.

Those sensors you purchased on Amazon? Do yourself a YUGE favor and send them back. If they won't accept returns, dig a very deep hole in your backyard and drop them in. Fill the hole and and then cap it with quick setting concrete, so you're never tempted to dig them up and try them. You definitely want to stick with a quality name brand such as Denso, Bosch, etc. Stay away from the house brands from discount parts chains, too. There's a reason quality parts cost more. We've had many sob stories on the forum about grief caused by cheap Chinese parts.

They look like wideband aka linear, and may well be OK for the upstreams.

It's a while since I looked but Denso had (have?) a tool to find the right ones. I suspect (am not sure!) 234-4798 will be the downstream (Jaguar C2C25956 I think) but do check.

With my car, I got a code saying that one of the downstream O2 sensors needed to be replaced. The car checks them for you every time you drive the car. I got a NGK one because I couldn't find a Denso O2 sensor like the original. The NGK one works fine. Don't get a cheapo brand. They are also easy to replace. The upstream sensor tells the car the condition of the CAT. The downstream sensor has to do with how the car runs. Fuel trim, etc.

Ooh, I think you've got the positions backwards. The upstreams are closest to the engine, and are the first sensors to sample the exhaust flow and report back to the computer, for adjusting fuel trim. The downstreams come later in the exhaust flow, and primarily monitor the performance of the cats. On 2003+ models, the downstream sensors also help fine tune the fuel trims.

Oh well, I guess that I got the wrong information before. Either way the car tells you which one needs to be replaced with a trouble code.