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DEF and NOX sensor trouble

15K views 25 replies 8 participants last post by  Fighterpilot 
#1 ·
Hi all,

Thought I would share my experienced with the dread DEF warnings and ask for some advice.

I've had my 2016 2.0D 163ps since January and I really like the car, however it hasn't exactly been smooth sailing. In March the DEF warning came up on the display and the engine count down began. I took the car into Jaguar who told me that the injector was the problem, which they replaced and updated the software. This didn't clear the countdown and so the issue was diagnosed as a faulty NOX sensor, which was replaced and corrected the issue.

Last week the engine management light came on, I was some distance from home so continued the journey. Jaguar couldn't book the car in until later this week but assured me that the car was safe to drive until then. I had long journey for work the next day and after about 70 miles, the light went out. I decided to take the car to an indie Jag specialist to be looked at in the meantime. They diagnosed that the fault relates to an issue with the new NOX sensor and that this should be covered by a 2 year parts warranty with the dealership. I've called the dealership and they have confirmed that the part is covered by warranty but that the Jaguar XE actually has two NOX sensors. Only the replaced part is covered by warranty and they wont know which is causing the fault until I bring the car in.

Is anyone aware if the Jaguar XE has two NOX sensors? I'm finding conflicting information on the internet.

I'm also concern that regardless of which NOX sensor is at fault, a bill will be coming my way! Does anyone have any experience of this or advice they can offer?
 
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#3 ·
I will have to check but wonder if this is the latest dealer scam to drag in money. They should know which Nox sensor is at fault by their diagnostics if 2 are fitted. I will have a look at the WSM and get back but it maybe late tomorrow. I have a very busy day in Derbyshire tomorrow so will not be able to look until then.
 
#4 ·
Thanks for the info, Ted. Really hoping its something simple or I might just have the dealership do the diagnostics and take it to an indie. The EML has actually gone out and its driving just fine so hopefully its nothing too pressing.

Could well be, Fighterpilot. If you can find any info, id appreciate it. I cant find anything specific to Jaguar but some diesel engines do have two sensor; one at the engine and another at the exhaust. Seems odd that one would fail and cause the car to shut down, whereas the other turns on the EML for about 100 miles with no other ill effects.
 
#8 ·
Dash.BD said:
So it does have two sensors! Or at least a sensor module and a sensor (seems like the same thing to me).

Thank you for sharing this, Ted. I really appreciate your help. Its back in with Jaguar tomorrow morning, will see what they find.
Two sensors and two modules according to the diagram
 
#9 ·
Indianajons said:
Dash.BD said:
So it does have two sensors! Or at least a sensor module and a sensor (seems like the same thing to me).

Thank you for sharing this, Ted. I really appreciate your help. Its back in with Jaguar tomorrow morning, will see what they find.
Two sensors and two modules according to the diagram
That is for the NAS market not EU6 models
 
#10 ·
From what I have on the engine, there is a pre and post sensor in the exhaust system. One is almost at the exhaust manifold and the other someway down the exhaust. So there are two similar to the other diagram on this thread. The diagnostics should state which is faulty, as that is what they are for.
 
#13 ·
I agree with Wastegate84. They are guessing as to what is wrong. To save money go elsewhere as the CC will fetch good money when removed to someone. I hate guesswork diagnostics. All through the manual JLR state substitution of parts should not be done in fault detection and to use the correct diagnostic equipment.
 
#14 ·
Luckily the car is still covered by a 6 month warranty from the garage I bought it from. They have the exact same concern and have requested JLR examine the system further with a borescope. I agree with them, a main dealer really shouldn't be saying "we think this is the problem".

The error reading found is 'NOx sensor - catalytic efficiency below threshold' so it does seem a bit lazy to just replace everything. Especially as the DEF injector and Nox sensor was only replaced 3 months ago.

They've also found a small oil leak but haven't been able to find the source yet, not sure if the two issues are related.
 
#15 ·
Is the oil leak around the turbo? Oil being carried into the exhaust will cause strange readings and may be an indication of turbo imminent failure. I think that correct diagnostics on JLR equipment should pinpoint the problem. That is what it's for. If it's now Nox sensor and catalytic converter, the next will be the turbo and MAF sensor at this rate of deduction. Persist with them fixing it and insist that all work after the warranty runs out for this problem is still under their warranty until finally sorted.
 
#16 ·
Fighterpilot said:
I agree with Wastegate84. They are guessing as to what is wrong. To save money go elsewhere as the CC will fetch good money when removed to someone. I hate guesswork diagnostics. All through the manual JLR state substitution of parts should not be done in fault detection and to use the correct diagnostic equipment.
Have a look though this Mongoose diagnostics info: https://www.jlridssddmongoose.com/home/jaguar-xj-xk-xf-f-type-mongoose-pro-j2534-diagnostics-kit-ids-sdd-jlr-v138-v131-cable-usb-16gb/

It would appear that the system they use is called SDD ( Symptom Driven Diagnostics). For accuracy it depends on ALL the end user reported symptoms being fed in to the computer by the technician. It will then spew out the most likely cause of the problem and how to fix it. Have you ever spoken to a technician when initially booking your car in at a dealer? Of course not. It's a very pleasant receptionist who jots down a few notes which then get passed on. It's no wonder they often get it wrong!!
 
#17 ·
BOBCDP, I suppose I have been lucky in having male receptionists at my dealer who actually had an interest in the cars and noted down all points I made. When the job was done it was "done" and that was that. If there was a point not findable it was noted by the techy and related back to me on picking up the car. From recent dealings with another dealer the service manager was a woman and hadn't a clue of where to look to get me service info. That was sad as I thought the outfit concerned was good. From reading feedback the after warranty service was more poor than even average or good. I agree that if the info given by the customer is not fully entered then the outlook is possibly going to be poor. In another scenario my wife presented at the GP with a mild rash and joint pain. The GP wanted hospital A&E to see her ASAP. The Dr there was straight from Uni with little experience. She was sent home. 2 days later we were back at the GP who rang the A&E and spoke to the senior Dr. The result was she was in a severe state of reactive arthritis which would have killed her if left untreated any longer as it attacks all internal organs and destroys them. Three weeks in an isolation room with drips of various concoctions she was finally allowed home. The rule should be listen and note down everything relating to the problem.
 
#18 ·
That's the thing, BOBCPD; other than the EML coming on and then going off, there was no other issue. The car drives great, accelerates well and delivers 55-68mpg. Thanks for sending the link, I will take a closer look

Thanks for the advice, fighterpilot. As near as I can tell it's only a very small amount of oil near the rear of the engine floor pan so it could be coming from the turbo. I haven't noticed any on my driveway or had any oil warning lights.

I'm still waiting on a call back from the dealership telling me what they have found and when repairs will be done, I suspect that will be Monday. The dealership tell me that any work they carry out is guaranteed for two years but I must admit this car is begining to worry me.

Sorry to hear about your wife being unwell and being misdiagnosed. I hope she is doing better now.
 
#21 ·
BOBCDP said:
Fighterpilot said:
I agree with Wastegate84. They are guessing as to what is wrong. To save money go elsewhere as the CC will fetch good money when removed to someone. I hate guesswork diagnostics. All through the manual JLR state substitution of parts should not be done in fault detection and to use the correct diagnostic equipment.
Have a look though this Mongoose diagnostics info: https://www.jlridssddmongoose.com/home/jaguar-xj-xk-xf-f-type-mongoose-pro-j2534-diagnostics-kit-ids-sdd-jlr-v138-v131-cable-usb-16gb/

It would appear that the system they use is called SDD ( Symptom Driven Diagnostics). For accuracy it depends on ALL the end user reported symptoms being fed in to the computer by the technician. It will then spew out the most likely cause of the problem and how to fix it. Have you ever spoken to a technician when initially booking your car in at a dealer? Of course not. It's a very pleasant receptionist who jots down a few notes which then get passed on. It's no wonder they often get it wrong!!
Well all praise to Lloyd Jaguar in Carlisle. When I took my XE in for some warranty work the receptionist actually went and got the technician to come from the workshop and discuss the issue with me. He then fixed it and when I picked the car up he again spoke with me to tell me what he'd done. Incidentally, this must also increase job satisfaction for technicians.
So not all Jag dealerships are poor, it seems, but JLR do need to root out the poor ones or somehow incentivise them to improve.
 
#24 ·
So dealerships says its the DEF filter and oil leak has been traced to a blanking cap. Warranty garage have agreed to pay for the work.

Still slightly concerned there may be something else that's being missed but that might just be that may trust in the car has been rattled.
 
#25 ·
Fighterpilot said:
Thanks for your reply. Later in the day it came down to 38.3C then lower again to 37.8C and today normal. Very weird but she has an emergency GP phone consultation and possibly blood tests.
Fingers crossed it's nothing to serious. There are a few bugs the doing the rounds besides covid, they are being blamed on lower immunity due to lack of socialising apparently.
 
#26 ·
All fine. It passed quickly but she is having a Covid lab test done anyway. A Dr called her Sunday to see how she was. By then the temp had gone and Monday our surgery contacted her to make sure she was OK as well. I must say I was impressed with the way she was treated as the Dr on Sunday spent 30 minutes asking various questions.
 
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