By popular request on another thread here, I thought I'd pass on my findings when trying to find a much cheaper way of replacing the Upstream O2 sensors on the X308 V8's.

From the 1999 Model Year onwards, the X308 engine management systems used 4 O2 sensors in the Upstream & Downstream positions. The Upstream sensors are 'Wideband' linear air/fuel ratio sensors & work differently to the more common 'Narrow Band' switching sensors. This allowed more acurate control of the air/fuel ratio over a wider range of mixture strengths.

However, these sensors need to run much hotter than the usual types & they have more powerful heaters. After a high mileage the heaters can fail, which throws up the EML light & sends the ECU into it's basic fuelling mode. The car will still start & run alright, but the fuel consumption will be noticeably higher & the 'edge' will go from the performance.

New sensors from Jaguar are hideously expensive, but after some research & experimentation on my own 2001 XJR, I found that the X-Type Jags used a very similar design which worked on the same principle & that the X-Type Upstream sensors from the V6 models will work in the X308 V8's.

As there are many more X-Types in breakers yards than X308's, there is a plentiful source of cheap used sensors available-especially on ebay. Prices are very cheap & a used sensor is typically around £30, maybe less if you're lucky.

Anyway, you need to look for the GREY plug UPSTREAM O2 sensors from 2001 year-onwards X-Type V6's, from either the 2.0L, 2.5L & 3.0L engines.

There is a Denso part number on the X-Type sensors I used: 9F472AA

I've tried this Upstream sensor on my own 2001 XJR when the original sensor failed. I reset the EML with my cheapo scanner & went for a drive-all the power was back & the car worked perfectly. Several months later & a few thousand miles later everything's still working fine & the EML light stayed off, with no stored P codes.

I didn't bother buying a new X-Type sensor, as there were so many cheap used ones on ebay costing around 10 times less than the proper new X308 part

I will say that the X308 & X-Type part numers for their Denso sensors are different & there may be detail electrical differences-but after several hundred miles of hard driving in my XJR with the X-Type sensor fitted, I've not had any obvious side effects-apart from maybe a slight increase in fuel consumption-but that may be my driving style & the the fact that the weather is colder

 

Good info indeed RO! ;o))
I am wondering if these same sensors will work on an AJ26 engine?
My car being an ROW model has only the heated 'upstream' sensors with 4 wires, 2 black, one white and one blue with the long grey plug.
These are a zirconium sensor i believe.
I also found some good cross referancing from this company in the UK:

Just Lambda, Jaguar lambda sensors, Bosch and NTK zirconia and titania sensors by post

And their prices seem OK too.
I managed to score two good O2 sensors for my car from Autoreserve Parts who has an e-bay shop
These werte from a very low mileage car that was parted out and are in excellent condition.
I think with my car approaching 200,000klm, I may think about replacing the o2 sensors but everything is purring fine and fuel consumption sits on around 11litres/100klm which I think isn't too shabby ;o))

 

Red, what mileage did you get the O2 failure? did you test the old one in anyway to confirm it was goosed?

I think the NA engines went to 4 sensor in 1999 and the R's a year later.

 

My sensor failed at 147k miles & the EML light came on suddenly-it was the LH sensor on UK models, which is under the coolant reservoir so it was a pig to change.

The fault code mine threw up was P1647, which is defined as 'Linear O2 sensor control chip'. This is just a fancy way of saying that the heater current was out of spec for whatever reason.

Anyway, I took the sensor out & measured the heater resistance-it had gone open circuit & that was why the heater current was out of spec, because there wasn't any as it had burned out

I did some research with the circuit diagrams & eventually hit on the idea of using the X-Type Upstream sensors instead, as an experiment.

All the earlier X308 V8's used the 2 sensor system-one for each bank of the V8. The sensors in this system were the very basic narrow band switching O2 sensors.

When they went over to the 4 sensor systems, the old 2 sensor system upstream narrow band sensors were then put in the downstream position to monitor the catalyst efficiency. The upstream sensors were then replaced with a completely different type, which was a wideband linear air-fuel ratio sensor that gave a current output proportional to the air/fuel ratio.

The new upstream sensors also had more powerful heating elements which drew a higher current & ran much hotter.

The 4 sensor systems had rectangular plugs & were colour-coded, with grey plugs for the upstream sensors & black plugs for the downstream sensors. The X-Type used the same 4 sensor system with the same plug shape & colour-coding.

Cheap universal sensors will NOT work in the upstream positions of the 4 sensor systems-they both work on different electrical principles & have completely different output signals.

The genuine upstream sensors for the later V8's with the 4 sensor systems are extremely expensive from Jaguar dealers. However, there are Jaguar parts suppliers on ebay which supply the genuine part (LNE1684BB) for much less at around £120, although that's still not cheap.

The X-Type upstream sensors are also wideband linear air/fuel ratio sensors, so I tried these instead from breakers selling used parts cheaply.

The actual part numbers for the X308 & X-Type upstream sensors are not the same, so I imagine there are detail electrical differences between them. However, they both operate on the same linear current analogue principle & both have the same very low heater resistance of around 1 ohm.

You can also identify them by the sensor end of the body-the wideband sensors have 2 small holes at 90 degree spacings around the body. The more common narrow band sensors have multiple holes all around the body.

The fault codes thrown up by failed heaters on the wideband front sensors are P1646 & P1647.

P1646 is not too bad as the sensor is relatively easy to reach on the RH cylinder bank.

However, P1647 is a pig to reach as you have to remove the coolant expansion reservoir at the bulkhead to get any access to remove the sensor...

The electrical plugs can be reached by removing the big plastic trim piece at the bulkhead which covers the flywheel bellhousing-the 4 sensor plugs are under this & you may need to remove the Evap valve & move the big electrical connector out of the way to reach the plugs.

I did it mainly for experimentation & discovered that the X-Type sensors do indeed seem to work fine in the V8's. The fault codes were erased & the EML light put out-so far they have not returned & all the performance is back again.

There are always auctions on ebay for X-Type upstream O2 sensors with the grey square plug, so it's quite cheap to pick up a used one & keep it as a spare.

 

This is interesting. I was wondering if anybody could read the output of the wide band O2 sensors ? My OBD reader and my UltraGauge don't seem to be able to read the upstream O2s, but will read the downstream ones.

 

The problem with reading the output of wideband sensors is that they don't give a voltage output. Instead, the ECU applies a fixed voltage to the sensor electrodes & then measures the sensor current flow. The ECU then converts this current flow into a voltage analogue internally & then uses that to determine the air/fuel ratio.

The old narrow band sensors would only work around the Stochiometric ratio of 14.7:1, with the output voltage swinging down to less than 0.2v with a slightly leaner mixture & then swinging to above 0.7v with a slightly richer mixture. The sensor would constantly 'cycle' between these 2 values & keep the air/fuel ratio around the Stochiometric point for the catalyst to work.

The wideband sensors were introduced to allow accurate mixture control over a much wider air/fuel ratio range, so the ECU could actually control the mixture strength outside the Stochiometric point instead of just applying 'fixed' fuelling values from maps in the older 'narrow band' sensor systems.

The big problem with narrow band sensors is they only allowed controlled mixture ratios within a very small range-outside of that range the ECU simply applied 'fixed' values if the driver demanded hard acceleration with a richer mixture. The mixture would be richened from the 'fixed' fuelling map in the ECU, but there was no way of telling how the fuel was actually burning inside the engine & if the 'richness' level was correct.

That all changed with the wideband sensors & the only side-effect of the design is that they have to run much hotter at around 600c instead of 300c for the narrow-band sensors. So they have to have more powerful heaters & so the heating elements are more prone to failing.

 

It was easy to read the output of the older narrow-band Zirconium sensors (apart from the Titania tyes though), as you only needed a high-impedance digital multimeter to read the voltage & make sure it was switching between the 0.2v level & the 0.7v level

You cannot do this with the wideband linear sensors as they run at a constant voltage & it is the current flow that changes-if you connect a multimeter to a linear sensor, all you'll measure is a fixed voltage. At the Stochiometric point the current flow is zero & swings one way for richer mixtures & the opposite way for leaner mixtures. So you'd need to cut the circuit physically & wire a sensitive current meter in series with the sensor output to measure the current flow, which is in the order of a few milliamps.

 

Do you see any difference in STFTs and LTFTs betwen banks?
According to the link I posted on the other thread
Oxygen Sensor - C2S51801G | Jaguar XK8 - XKR, Jaguar X Type | Jaguar | British Parts UK
the JAguar part is identical for X type and XKs.

 

I've not been able to look at the fuel trims as my scanner was just a cheap & cheerful one to read the P codes & extinguish the EML light. I think that the fuel consumption is about 1 or 2 mpg higher now, but it's hard to tell as the cold weather & recent short drives will drop the fuel economy anyway. The actual engine performance is back to normal & it starts/runs fine.

When the original sensor failed, the EML light came on & the P1647 code was thrown up. The fuel consumption went up noticeably & the edge disappeared from the power.

I even did a stall speed test to see what speed the engine could drive the torque converter with the car braked fully in 2nd gear. The indicated RPM's were 1500 when the sensor failed & the EML light was illuminated, and 1800 when the sensor was replaced & the car back to normal.

When the sensor failed the car lost it's performance edge-it was still quick, but not rabidly so in the manner of a healthy XJR. Once I put the X-Type sensor on, all the power was back & it would light up the back end once again over rough road surfaces

I couldn't find any manufacturers data for the actual electrical characteristics of the X308 & X-Type linear O2 sensors, although they both have the same circuit diagram symbol which was different to the narrow band Lambda sensors. The both also had the same physical appearance in every way, from body style, plug colour & shape, lead length & location/number of holes around the sensor body to 'breathe' the exhaust gasses.

 

Great info, worthy of stickie status.

Thank you button clickies too

 

how do
brand new to forum and jaguars. am i going mental or are the downstream and upstream identical apart from wire length and colour of the cap ...are we being had over by manufactures ?? just asking before i change it..as i have a spare downstream (black cap) will it work ???

 

Car details?

 

ta very much i shall attend to it asap ..told you i was new ha

 

if this helps my car is 2002 x-type 2.5 petrol v6 ..am just finding my way around the forum at the moment ,but would appreciate any help in the mean time thanks

 

OK, will try to help but you've posted in the wrong forum and your car is vastly different.

You should be in the X-Type forum X-Type - Jaguar Forums - Jaguar Enthusiasts Forum

I'm fairly sure the up & downstreams are utterly different internally. When you've more posts grab JTIS which shows them and/or JEPC (ditto).

If I'm right then whatever you do make sure NOT to fit the wrong type.

 

In the process of changing the upstreams on my X-type right now, but for information's sake, the Denso sensors are the same item; the different parts numbers have different lengths of wire on them! The X-type sensor happily fits YOUR car because the slightly longer wire is the only difference

 

Hi, I thought I'd post this which is a description of how I removed the O2 sensor in my 1998 XJR. Hope it's useful:

http://www.inclusivechoice.com/Temp/...gO2Sensor.html

 

My wife's 2002 X-Type w/ 3.0 liter engine gives a P1647 code. As I have figured out from your information, this is an upstream sensor; upstream, meaning the sensors located nearest the engine. Complicating things, I now realize that there is a sensor for the radiator bank and one in the firewall bank. Does the P1647 code refer to the radiator or firewall sensor? Or, if this code doesn't indicate which one, how am I to determine which sensor is the bad one?
Thank you,
Dave