Xantia V6 broken exhaust (update: and rough low rpm running)

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addo
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Post by addo »

If you've got gas in the aircon, see what happens with the AC on and engine idling in N. It may no longer retard the timing.

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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

In all the gearbox fun I forgot to mention there might be something up with my new oxygen sensor. #-o

The Lexia showed "Intermitent: Oxygen sensor open circuit" the other day out of the blue, however when I checked the live data for the oxygen sensor it was working.

What I did notice though is that the voltage wasn't swinging through the full range - it was only going from about .35v to 0.65v. :? I disconnected and reconnected the plug and it seemed to improve to about 0.2v to 0.8v, so possibly a poor connection.

Even when I first fitted the new sensor it seemed to me that it takes a long time to warm up. Even though the old sensor was sluggish to switch, it did seem to warm up quickly, typically 30-40 seconds from starting just left to idle and it was switching through the full voltage range of 0.1 to 0.9v. The new sensor has always taken a lot longer to warm up, I noticed it the day I fitted it, and I re-checked it recently and it takes a good 2 minutes after a start before it is switching properly, however if I rev the engine up it warms up a lot faster, maybe 40 seconds.

This to me suggests that the heater isn't working (relying entirely on exhaust heat) or isn't working properly, causing a slow warm up time. If it wasn't working at all I would have thought it would log a heater fault code (one does exist for the ECU) and that has not happened. When cold oxygen sensors are high impedance (more or less open circuit) so if it was taking a very long time to warm up the ECU might give up waiting and assume the sensor was in fact open circuit when it just wasn't warming up quickly enough.

The plug on the new sensor had the bump on the wrong side of the plug which I had to shave off, I'm wondering whether the contacts are a poor fit as well causing high resistance connections to the heater circuit ? :?

Has anyone had this sort of issue before ? I do still have the original plug with 15mm stubs of wires in my toolbox, if it is a poorly fitting connector I could graft the original plug on...

larppaxyz
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by larppaxyz »

Hi, just a update to my idling issues and so on. I removed air box to see knock sensor connector, there was no visual damage or anything, but i unplugged and plugged it few times anyway. I also had to remove air intake temperature sensor connector while removing air box. Earth cable was visible going to engine and i moved it around a bit to see if it was loose (it was not). After this, car has been working again without any issues, no unstable idle, no bogging on 3k RPM, much much snappier overall ... we see how long this lasts..

PS. Mandbrake, thanks for torque reduction information testing few posts up.

PSS. I have had my oxygen sensor replaced year ago.

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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by larppaxyz »

Mandrake wrote:In all the gearbox fun I forgot to mention there might be something up with my new oxygen sensor. #-o
This to me suggests that the heater isn't working (relying entirely on exhaust heat) or isn't working properly, causing a slow warm up time. If it wasn't working at all I would have thought it would log a heater fault code (one does exist for the ECU) and that has not happened. When cold oxygen sensors are high impedance (more or less open circuit) so if it was taking a very long time to warm up the ECU might give up waiting and assume the sensor was in fact open circuit when it just wasn't warming up quickly enough.
Heating is controlled via relay, so you should be able to measure it from relay without going under car. Btw, when replacing your oxygen sensor, did you pay attention to fact that external clean air reference is obtained through oxygen sensor signal and heater wires, meaning you can't solder or completely cover connections.

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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by CitroJim »

Indeed, heating is controlled by one contact on one of the double injection relays...

Never knew that about the wiring providing the reference air....

Simon, just out if interest I fired my XM up from cold watching the oxygen sensor on the ELIT and it took only about three minutes before the signal started moving but perhaps five before it started moving over its complete range...

I've seen another Xantia V6 with a replacement sensor show exactly the same fault as yours but when I last ELIT'd it the fault was clear and the sensor working as expected.

Did you replace yours with an ebay el-cheapo special?

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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

larppaxyz wrote:Hi, just a update to my idling issues and so on. I removed air box to see knock sensor connector, there was no visual damage or anything, but i unplugged and plugged it few times anyway. I also had to remove air intake temperature sensor connector while removing air box. Earth cable was visible going to engine and i moved it around a bit to see if it was loose (it was not). After this, car has been working again without any issues, no unstable idle, no bogging on 3k RPM, much much snappier overall ... we see how long this lasts..
Hi,

Thanks for getting back with those results, very useful. :)

I think it adds further strong evidence to my theory that the intermittent poor performance and "bogging" at low RPM that we've both experienced, along with many other identical symptoms like the RPM fluctuation and idle stability are in fact caused by the knock sensor control signal causing the ECU to retard timing when it shouldn't. My video showing torque reduction retard alternating between 0 and 15 degrees at 1200rpm in time with the idle going up and down I think proves it is timing related, and now that we have ruled out the gearbox torque control line that leaves the knock sensor signal.

Exactly what the cause of the false knock information is we don't know for certain but it could be a few things or combination of things:

* Broken earth/shield on the knock sensor cable. Even though the cable looks fine on the outside the screen/shield inside the cable may be broken, so when the cable moves slightly due to vibration or due to work being done on the car in the air box area the shield connection makes or breaks. The signal level from the knock sensor is so low and with high source impedance and the ECU input so sensitive that unless its thoroughly screened with shielded cable and earthed correctly at the end it will pick up ignition interference and other electrical noise from within the engine bay causing false triggering of the ECU knock input. The knock cable from memory has a signal wire, a signal ground and then a separate screen ground around the two of them, hence the 3 pin connector.

* Corrosion at the connector, causing similar problems to a broken screen in the cable. Any of the three connections being intermittent would cause problems due to the sensitivity of the ECU on this input. This seems most likely the explanation for your car since reseating the connector helped. (You should try to use some contact cleaner on the connector if you can, or if the symptoms return)

* Faulty/loose knock sensor.

* Mechanical noise being picked up besides knocking, for example noisy tappets or other metallic engine noises in the block. I think this could be partly my issue as I had very noisy tappets, since using an additive that has quietened the tappets there does seem to be quite an improvement. Although not perfect the symptoms of "bogging" and low power at low RPM are quite rare now, whereas before they were occurring nearly all the time. However like you when I had the air box off and disturbed the wiring the car sometimes went extremely well for a few hours or days then became poor again.

The last time that the car went 100% with no hesitation at all and lots of power was when I had the air box out and the cruise control diaphragm bracket loose and moved aside so I could connect my fuel pressure gauge to the fuel rail - and this is right in the area of the knock sensor wiring and connector, so I probably disturbed the wiring...

You might find this video on knock sensor retard interesting, I may have posted it before, but it shows just how badly an engine can lose power and "bog" (to the point where it can hardly climb a hill) due to 20 degrees of false knock sensor retard:

" onclick="window.open(this.href);return false;

Just in the last couple of days I've noticed that immediately after a cold start the car is reluctant to accelerate up a hill in first gear (I now park on a hill and drive up the hill towards work) it will seem to bog a bit below 3000 rpm but if I keep the throttle down about half way it will after a second or two suddenly pick up and zoom away like a scalded cat...

I'm thinking that I might be seeing some false knock sensor activity creeping in again, I will be changing the engine oil next week, and I will also be scrutinising the connection to the knock sensor carefully. What I might try is to back probe the engine ECU connector again with the scope and measure the knock signal where it goes into the ECU while the engine is idling and/or held at 1200rpm, and then try wiggling the knock sensor connector to see if there is any change in the signal or the idle stability - if there is I'll know I've got a cabling/connector problem...
Last edited by Mandrake on 04 Jun 2013, 11:57, edited 2 times in total.

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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

larppaxyz wrote: Heating is controlled via relay, so you should be able to measure it from relay without going under car.
Thanks. The only problem with measuring it there if trying to confirm a poor connection is that I'd have to measure the current drawn by the heater, not the voltage at the terminals, and I don't know what the "normal" heater current is. Does anyone know ?
Btw, when replacing your oxygen sensor, did you pay attention to fact that external clean air reference is obtained through oxygen sensor signal and heater wires, meaning you can't solder or completely cover connections.
I bought an oxygen sensor with a plug already fitted, so I have not spliced any wiring yet or covered anything up. I knew that the reference oxygen entered via the wires, but are you sure its through the end of the wires where it goes into the connector ? I was under the impression that the air leaked in between the outside of the wires and the rubber sleeve at the oxygen sensor end of the cable - hence the recommendations not to get grease on the outside of the sensor. (Thus blocking the air leaks near the wiring exit)

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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

CitroJim wrote:Indeed, heating is controlled by one contact on one of the double injection relays...
Thanks. :) I'll check the wiring diagrams to see where exactly. Only thing is I don't know what current the heater normally draws, checking the voltage at the relay wouldn't tell me about any high resistance connection at the oxygen sensor connector but if I had a known good current reading I could compare that...(it could be that the current is high enough to make the ECU happy but not enough to heat the sensor fast enough)
Never knew that about the wiring providing the reference air....
Yep, although I thought the deliberate air leak was between the wires and the rubber sleeve on the sensor...
Simon, just out if interest I fired my XM up from cold watching the oxygen sensor on the ELIT and it took only about three minutes before the signal started moving but perhaps five before it started moving over its complete range...

I've seen another Xantia V6 with a replacement sensor show exactly the same fault as yours but when I last ELIT'd it the fault was clear and the sensor working as expected.
3 to 5 minutes ? That's odd... :? My original sensor was absolutely definitely warmed up in less than a minute while idling and switching over the full voltage range, even from a cold start in the morning...

The new one is much slower to warm up especially at idle, at least two minutes before its switching and even then it takes another minute or so before its swinging across the full voltage extreme. :?
Did you replace yours with an ebay el-cheapo special?
Nope, it was a £65 Bosch, supposedly OEM type with connector! And yet the connector had the bump on the wrong side of the plug so I had to shave it off for the plug to fit... which is why I'm wondering if its not quite the right model for the car and there could be differences in the heater specs....maybe it just has a lower wattage heater but will otherwise work ok.

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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by CitroJim »

The reason why soldering on Oxygen Sensor leads is not recommended is because it's never recommended anywhere on a car. The act of soldering makes the wire brittle at the boundary between the original copper and the solder. Vibration will soon see it fracture..

Also, a good deal of heat will travel up the oxygen sensor wires and even if this does not outright melt any soldered joints then the heat will make them deteriorate to the extent they'll end up dry.

The heat is the reason for PTFE wires in the first place and why the connector is always a long way away...

Indeed you are right Simon, reference air bleeds in at the top of the sensor down the outside of one wire..

My timings were measured on an idling engine so it's going to take longer...

Swapping a knock sensor is a major task. Swap your oil first!!!

The knock sensor is just a piezo microphone. Rig up a 'scope to it and see what's coming out of it :wink: If there is mechanical noise you should see it...

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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

CitroJim wrote:The reason why soldering on Oxygen Sensor leads is not recommended is because it's never recommended anywhere on a car. The act of soldering makes the wire brittle at the boundary between the original copper and the solder. Vibration will soon see it fracture..

Also, a good deal of heat will travel up the oxygen sensor wires and even if this does not outright melt any soldered joints then the heat will make them deteriorate to the extent they'll end up dry.

The heat is the reason for PTFE wires in the first place and why the connector is always a long way away...
If I were to splice the old plug onto the new sensor, what would be the best way to join the wires then Jim ? I come from an electronics background so I'm used to soldering and I'm not fond of crimped connections... :lol: I'm not sure what type of crimped connections or joiners I'd use to join oxygen sensor wires ?
My timings were measured on an idling engine so it's going to take longer...
So were mine, the original oxygen sensor was active in about 30 seconds and fully warmed up in under a minute at idle, from a cold engine. Perhaps there are differences between different sensors, maybe some of the after market ones don't have very good heaters ?
Swapping a knock sensor is a major task. Swap your oil first!!!

The knock sensor is just a piezo microphone. Rig up a 'scope to it and see what's coming out of it :wink: If there is mechanical noise you should see it...
Indeed, I'm well aware of what a nightmare of a job it is to get at it! :evil: I'll be changing the oil and filter next week so we'll see if that helps. I'll try to put my scope onto the knock sensor signal at the ECU before and after changing the oil to see if I can notice any difference...should be interesting! :) Knowing my luck I could have both mechanical noise AND electrical noise on the knock sensor signal. :twisted:

While searching for knock sensor info on the ES9J4 I stumbled across this, VERY COOL: :mrgreen:

http://www.dp-engineering.nl/vems-pnp-p ... 4-xfz.html" onclick="window.open(this.href);return false;

It's an after market ECU pre-tuned and drop in compatible for the ES9J4, but fully programmable and tunable in every possible way, right down to editing the fuel mapping tables, timing tables, knock sensitivity etc... it can be used with standard sensors, or some sensors can be upgraded such as higher pressure MAP sensor for turbo applications, a wide band oxygen sensor instead of narrow band (allowing the possibility of running in closed loop at all load conditions) and so on... complete with massive amounts of telemetry data which can be monitored in real time or stored on-board and retrieved later, and an optional heads up display. Basically bringing the ES9J4 electronics into the 21st century. :lol: Just take a look at the screenshots of the software... 8-)

Of course it would be a complete waste of money on my old banger at a smidgen over 800 euros :shock: but I could see the use for it in a top condition car like a manual V6 Activa conversion where you're trying to tweak every last bit of performance out of it. :twisted: One other benefit would be that I'm sure it would eliminate all the hassle of having to pair with the CPH and obtain a manual ECU and then unlock it as I'm assuming it would be "unlocked" by default...

Pretty neat anyway, and I'm fairly sure this will be the ECU that was used in that 406 Coupe ES9J4 turbo conversion I posted a while back, since its the same engineering firm... :)

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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by CitroJim »

Mandrake wrote: If I were to splice the old plug onto the new sensor, what would be the best way to join the wires then Jim ? I come from an electronics background so I'm used to soldering and I'm not fond of crimped connections... :lol: I'm not sure what type of crimped connections or joiners I'd use to join oxygen sensor wires ?
Standard red butts are fine Simon but don't use an el-cheapo Taiwanese crimp tool as they are all rubbish and do terrible crimps. Use a pukka one like one of these:

Image

Butts, in case you don't recognise the term, are these:

Image

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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Well everyone who was concerned about the lack of engine oil changes can now rest easy, the engine oil and filter are now done. :twisted:

The day didn't go without drama though, thanks to a very stupid mistake on my part. :oops: As I was also doing the gearbox oil additives the first thing I needed to do was to add the gearbox flushing additive and take it for a 10 minute drive before draining the gearbox oil. Because the oil level was right near the top mark I decided I didn't want to chance just adding the 300mL worth of additive without draining a cup full of oil out of the gearbox first...big mistake. :(

I was trying to drain 300mL into a measuring jug with the sump plug mostly out but didn't bargain on the fact that because we'd already been out and about that day visiting a park the oil was probably over 100 degrees, was burning my finger tips and I lost control of the sump plug when there was only a 1 litre measuring jug underneath. #-o By the time I grabbed the draining tray which was out of reach there was about 2 litres of oil on the ground. :roll: The swear words could probably be heard for miles! :twisted:

Not only did I make a hell of a mess, it meant I wasn't able to use the flushing additive as planned, as that needs to be put in and driven before draining and I now had no way to stop the sump completely draining and only enough oil for one re-fill. Sigh. So I forged ahead and added the 300mL worth of Lubegard Platinum, and exactly 3.7 litres of LT 71141 to make up the difference.

The moral of the story is (a) have the full size drain pan underneath or within reach whenever fiddling with the drain plug, even if you think you aren't going to take it right out (b) don't try to drain 300mL out of the gearbox especially when boiling hot, chances of that going well are slim and two of my finger tips have the blisters to prove it. :lol:

I then went for a drive before changing the engine oil so as to get an idea of any change in driving characteristics with only one thing changed at a time. There was an immediate change in gear shifting quality which had become a bit abrupt in the last month or so, with smoother changes.

The other thing I noticed particularly after I'd done a bit more driving later in the day was that gear-changes are much quicker, particularly if you kick down to a lower gear, the gear change and power take up is positive and almost instant but still smooth. Previously the power take up during wide throttle kick down was quite delayed with a significant amount of "dead air" during the change.

Later on I did an auto adaptive reset which seemed to make things worse, in hindsight I should have just left it to learn by itself. It seems like a reset may be counter productive for a gearbox that is as far out of spec as mine, as the default parameter table is a poor match for the actual characteristics of the box... eventually it relearnt itself back to about what it was before I did the reset, but it took over 30 miles of driving to do so, and I'm not sure its quite as good yet as it was just before the reset.

So far I'm giving a cautious thumbs up to the effects of the Lubegard, especially considering I never got to use the flush before draining. It's taken the harsh edge off the changes, gear changes seem quicker and more consistent, I've also had no "slip bang" changes from 2nd into 1st when accelerating hard just as I'm drifting to a stop at a roundabout, which were starting to occur worryingly often before. No torque converter clutch shudder either, even when the oil is fully up to temperature.

Bear in mind that the oil got changed as well I didn't just add the additive to the existing oil, however given that I changed the oil by itself only a month ago and didn't see any of the above changes (except the reduction in torque converter clutch shudder) I think its safe to attribute the other changes to the additive. I'll monitor the behaviour of the box to see what the long term outcome is as its early days yet.

Next I did the engine oil and filter. The oil that came out was predictably black and horrible compared to the light and clean gearbox oil, the old engine oil filter was definitely one of the smaller ones, the new one was a good bit bigger in diameter but went on with no trouble. I put about 4.8 litres in as Jim suggested, ran the engine for a few minutes, let it sit a few minutes, checked the level and found it just below the top mark so decided to leave it at that. (Especially after the gearbox draining farce!)

The tappets seemed about as quiet as they were with the old oil and additive - maybe one or two making a slight noise but nothing major. I decided not to add any additives for now and just see how things go with the new oil on its own.

After doing the oil change I of course went for a quick test drive, the interesting thing is that when I first drove off down the road the car was going like an absolute rocket - far more responsive on the throttle and willing to accelerate than it usually is, after a few minutes of driving it faded away again back to its more regular slightly sluggish performance.

As well as the engine idling for a few minutes before driving, the air filter box had been off during the gearbox oil changes - for some unknown reason both of these actions usually result in much better performance, temporarily...

I'm convinced that I still have a problem with the knock sensor signal which is causing intermittent reduction in engine performance, so I think my next step is to get my scope on to the knock sensor signal line and check the wiring around the knock sensor connector carefully, to see if moving it changes the signal, and perhaps even tighten the appropriate female pins on the ECU connector.

I'm bouyed by the results "larppaxyz" had after checking the knock sensor connector on his car, he had identical but even more severe and persistent symptoms than mine which had not responded permanently to anything else he's done to the engine, yet just fiddling around with the knock sensor connector seems to have cured it for him.

Another evil trick I have in mind to see if it is a false knock signal that is reducing performance is to temporarily try shunting the sensor with a high value resistor (on the order of 560k) to cut down the amplitude of the knock signal a little bit. As far as I know most knock sensors (which are basically piezo microphones) do already have an internal shunt resistor in parallel with the piezo element to help minimise electrical noise pickup etc.

I can't just unplug the sensor completely as the computer notices there is no knock signal at all, logs a fault code and knocks the timing back permanently causing a very obvious loss of performance. (tried that already) But if I pad it down a little with a shunt resistor so there is still enough activity for the ECU to believe the sensor is ok, it may work. I think its fairly safe to try while I'm running on 99 octane fuel as well.

Does anyone have a known good ES9J4 knock sensor that they can measure with an ohm meter to see what value the internal shunt resistor is, (measured on the car at the green connector is fine!) or indeed whether it does even have an internal resistor ? If it does have one it will be somewhere around 560k judging by the knock sensors from other makes of car.

An open circuit internal resistor could lead to an "over sensitive" knock sensor that is both oversensitive to mechanical noise (since the piezo element is not loaded down as much as usual) and more sensitive to electrical noise pickup through lack of termination, so it would be nice to know what the correct resistance is so I can check mine. :)

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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by isisalar »

I've been waiting with bated breath the outcome of adding the Lubegard, I was sure it would improve things and I'm really glad for you that it has. It really is wonderful stuff and if you can wring a few more years out of the box it's well worth the modest cost.
On the engine side of this thread, given that the increase in octane rating has helped so much I would recommend you give a dose of this a try:-http://www.ebay.co.uk/itm/SLICK-50-FUEL ... 0815977456
Like Lubegard all sorts of claims are made, and in my experience are mostly true. I suspect that it does also increase the octane rating of the fuel as when it's in the tank every car Ive ever used it on has been smoother and performed better. The lasting effects vary depending on the problem. My HDI is currently running on a treble dose as a last ditch attempt to cure a noisy injector before I bite the bullet and go for new injectors, not as noisy as it was but still clicking, car's going like stink though. If your engine likes octane it'll love this stuff.
I'm generally very sceptical about additives and these are the only two I would recommend through personal experience.
As a matter of interest the place I get the slick 50 from, who I trust implicitly, are selling a £35 liquid head gasket repair kit, guaranteed to work or your money back.The mind boggles. They've not had to give any money back yet. One failure was due to mis application, a free replacement and correct application cured it. Last I heard they'd sold about 40, the wonders of modern science!!!!!
Cheers
Paul

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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by CitroJim »

I've been there with drain plugs and too-small containers Simon. It's why I always use a bund in the form of a very large cat litter tray now whenever doing anything involving the draining of fluids..

I absolutely detest and hate oil spills on my drive (as some who have visited and spilled have found out :twisted: ) and get very angry with myself when I accidentally spill any oil.

Good. I'm pleased you've finally done the oil :-D

I'm a tad worried about reducing the knock sensor signal in case you cause damaging detonation if the ECU tries to push the advance too far...

You won't read anything on a knock sensor with an ohmmeter as it's a piezo crystal and will therefore read open-circuit...

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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

It shouldn't be able to detonate on 99 octane, even with the maximum allowed advance mapping.

Are you sure there isn't a parallel resistor inside the knock sensor Jim, have you measured it to check ?

I've done some research on knock sensors and most makes (including Subaru, Ford and others) have a shunt resistor of approximately 560k inside the sensor, with part of the troubleshooting process being an ohms check. Some cars even use a DC bias current from the ECU to measure the presence of the resistor and log a fault if the correct bias voltage isn't detected, on the assumption there is a wiring fault or missing sensor...(the ES9J4 does not use a bias current though, that much I know)

Could you (or someone else with a known good ES9J4) check for me at the engine ECU connector ? I believe its between pins 11 and 30. I'm going to check mine today but I don't have a known good reading.