Question on O2 sensors, I did a search.
 

I couldn't find what I was looking for when I searched so I'll just ask. So Im getting codes for O2 sensors, I want to replace all 4 at one time as I keep getting the P0426 code and she does have a slightly rough idle. Figured, do them all and its like new.

I went to Rockauto and it seems they range (for daily driver category) from $70.00-almost $130.00 ($90ish is midline). The economy ones are all in the $70.00 range but I really don't want those. Is there a difference between the economy and DD ones that are both in that $70ish range ?

So whats everyone using as replacement. Car travels 1500 miles a year at most just turned 80K, 06 XJR. I figured I would clean the SC while I am doing the other work too just because its time.

Thanks in advance.

Use Denso only. These are your replacements for 06 XJR. Free ship

https://www.partsgeek.com/gbproducts...ad=47433948012

https://www.partsgeek.com/gbproducts...ad=47433948012

From Denso - Search Results:

2006 Jaguar XJR V8 4.2L

234-9125 Engine: V8 (4.2L)CC: 4196 Qty:2
Label: OE Style
Position: Upstream

234-4951 Engine: V8 (4.2L) CC: 4196 Qty:2
Label: OE Style
Position: Downstream

I would support Box recommendation from experience. Just went through the annoying process to change O2 probes back and forth myself because I thought I could save a few euro.

Actually, the downstream cat probes are simpler 2-point sensors that are easier to replace by aftermarket parts and don't affect the engine control directly. They just check if the catalyst is still good by measuring how fast oxygen variations from the upstream sensor are showing at their place. If oxygen level fluctuations directly hit through to the downstream sensor this means the catalyst has lost a big part of its oxygen storage capacity, meaning it's end-of-life.

But the upstream sensors are actually broadband sensors, measuring not only if the mixture is above or below lambda 1 (jumping), but they measure where exactly it is in a wide range (continuous signal). The cheap aftermarket parts I have tried so far were not capable of that and resulted in a immediate P1646, O2 sensor bank 1 not working as it should. That fault is then immediately deactivating the complete lambda control system, leaving the car running open-loop controlled by the MAF signal alone. And of course you have the MIL shining at you.

I circulated probes 3 times now until I returned the cheap crap and installed proper ones. That being said, you may very well be lucky with a cost efficient aftermarket sensor, but chances you have to lift the car a second time (or squeeze under it in my case) are substantially bigger than with the original part.

Thanks and I had a 10% off coupon for Rock Auto which got me these 4 at just under $275.00. Even with the free shipping (for me) parts geek was over $300.00. Not being cheap just smart, LOL.

On my quite old Jaguar, that latter part's not true - they provide fine control of fuel trims.

It's described by Jaguar in their workshop manual.

I'd be surprised if they don't do it for these car models as well.

With those kind of miles I am not so sure they are your O2 sensors. Have you looked at live data on the O2 sensors and on your fuel trims? I would be looking for signs of some sort of air leak first. What kind of scanner are you using to pull your codes?



I could be wrong but you have fairly low miles for bad O2 sensors, but have aged rubber parts that could be the cause of the problems (or maybe spark plugs or even old gas).



I hate to see you waste that 10% coupon and $275.00 and not solve your problem.

Well, standard and widely used application is that the first probe is the control probe and the second one the diagnostic probe. The second one, located behind the catalyst, has too much lag to effectively direct control the injection amount due to the oxygen storage characteristic of the catalyst.
The diagnostic probe mainly feeds the OBD with information on the function of control probe and catalyst.
With my non-functional control probe there was no activity on the short-term-fuel trims anymore but still slow adaptations of the long-term-fuel-trims, so lambda control was not totally deactivated. But in comparison to the activities with real working control probe that's just a failsafe function to avoid total run-off due to parallel MAF problems.

So yes, you are right that that also the diagnostic probe does provide a signal that is considered for control in case the control probe is on vacation. But I find it hard to believe that they do more when the real probe is active. I'll try on occasion tio disconnect the downstream diagnostic sensor to check what the fuel trims will do then. But I can't promise that for anytime soon. Glad I don't have a real reason to squeeze under the car for the time being :)

It's not used in the way you seem to say. A vacation has nothing to do with it.

It's definitely in the jag workshop manual that's on this site. I haven't looked for this specific car model.

It's also done by other car makers e.g. BMW, Audi.

If you disconnect one it will defeat this aspect entirely so what would be the point?

(Anyway - it's all irrelevant to the OP.)