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Mike, Technician
Category: Car
Satisfied Customers: 39198
Experience:  Tech Expert
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I have a 2006 MY Jaguar 2.7 Diesel S type. Reliable after 14

Customer Question

I have a 2006 MY Jaguar 2.7 Diesel S type. Reliable after 14 - 20 miles the dreaded restricted performance light comes on. The initial fault was on bank B maf sensor according to the independent dealer. Since then it has reappeared but the fault code reader I used and the Autologic box the dealer uses bothe failed to identify individual banks. The autologic said intermittent circuit fault or words to that effect. The car has been back 3 times since and the fault has failed to be found. Any ideas? I am a competent electonics qualified person and understand the circuits for the 2.7 diesel.

John Meredith
Submitted: 4 years ago.
Category: Car
Expert:  Shantal-Mod replied 4 years ago.

Hello John,

I've been working hard to find a Professional to assist you with your question, but sometimes finding the right Professional can take a little longer than expected.

I wonder whether you're ok with continuing to wait for an answer. If you are, please let me know and I will continue my search. If not, feel free to let me know and I will cancel this question for you.

Thank you,

Expert:  Mike replied 4 years ago.
Hello and Welcome -

My name is MIKE - Im happy to help you with your issue here..

Can you just tell me John --do you have any actual fault codes... from your tester or theirs...?

Plus - what mileage does your car have - and what is its service history like?

Rgds, MIKE.......................................
Customer: replied 4 years ago.

unfortunately I do not have the actual fault codes but when the fault first happened it was after the MAP sensor had been replaced by an independent Jaguar dealer. His autologic box had diagnosed this was faulty so he replaced it.I then drove the car home about 15 miles and the restricted performance light came on so I took it back immediately and the autologic box indicated it was the MAF sensor on the B Bank. The garaged swapped it around and the car ran fine for a few weeks and eventually the fault came back with restricted performance indicated. Once again the fault code indicated the B bank sensor was faulty so it was thought to be a wiring fault. The dealer once again investigated and could find no fault. The car ran fine afterwards and I took it on a long run of 150 miles and 40 miles before I completed the journey it went into restricted performance after I floored the accelerator leaving a bridge toll. I took it back to the garage and the box said MAF circuit fault but could not see the individual sensors. Once again after investigation the car ran fine for 100 miles before it happened again. I had it trailer-ed back to the dealer who has been unable to identify the fault twice since. I will take it back again but suspect it is the same fault. I do not have a code reader at the moment but when I visited Gendan they tried their top of the range box on it and that too fail to identify the individual sensors but also indicated MAF circuit fault. The dealer has since tightened up the connectors but the fault has still remained. I have had the car from new in 2006 and until 4 years ago it was dealer serviced. It was recalled at about 2000 miles to have the turbos replaced by Jaguar and a couple of months out of warranty at 16000 miles it went into restricted performance mode. Jaguar read the fault codes p244B-00 and P2453-00. The info from the Jaguar approved dealer said:carried out checks and found oil level too high and NS port deactivation valve not holding pressure. Replaced port deactivation valve kit. They also gave me a booklet from Jaguar about looking after your DPF and enquired on my journeys which at the time was 10 miles to and from work including standing traffic at points. The commented that could be detrimental to the engine. Needless to say I knew nothing of this from the salesman. Recently the gearbox has been replaced because the coolant leaked in to the gearbox lubricant and destroyed it. Another Jaguar design fault I believe.

Expert:  Mike replied 4 years ago.
Hello again John -

Thank you for your reply and info..

The problem you have is going to be down to a fault in that loom / that circuit that goes to the Maf etc. - the Pcm ( management computer ) , or a faulty MAF itself.

Its very possible that the MAF that was replaced is faulty.. I would put this too them - there have been reports of some Maf sensors, Bosch ones that have been faulty - those supplied through dealers - and the suggestion has been to get them of late from a Bosch supplier direct.. Your garage will know how to do that - I certainly think that is a way forward here first - as the loom replacement isn't cheap...

So I would discuss that with them first - then If thats not the issue proven - it has to be either a loom fault or a PCM fault..Again, both are not unheard of. The loom would need careful checking through - the wires tend to break down inside the loom insulation to it means stripping the loom back to find any such issue....

If thats what's found, thats that - but if not- then the next step would be to have the Pcm sent off to a specialist company for test and subsequent repair..

So those are the ways to work forward on this one now John - Im sorry there isn't a "it will be this or that ".. but its going to be one of the above - its now a case of tracing it down manually as above.

Best Rgds, MIKE.

Let me know if you need anything else..

Meantime - please do click on the OK rating to Excellent ratings service for me now, Thank you for that... and you can get back to me anytime if you need / wish..

Best Rgds, MIKE.

Please note, you are rating the content of my "answer" - my help to you - not the "system" which can experience delays etc which are not under my personal control -or delays caused by "time -off" which we all have on occasion - Thank you.
Customer: replied 4 years ago.

Hi Mike,

Happy New Year and many thanks for your answer. My main concern is the reliability of the restricted performance light coming on. When returning home from Christmas on mainly A roads with a couple of miles of dual carriageway the car goes into that mode within a 100 metres of the same spot. On motorways it takes a little bit longer but still predictable. It seems to me it is when the vehicle is fully warmed up. With a broken wire in my experience the fault would tend to come and go in the initial stages of failure. It may also be affected by movement of the loom caused by flexing of the vehicle body or the engine under load. If the car is left overnight or possibly shorter, the fault disappears and the fault is stored in the memory. I will have a poke around because according to the wiring diagrams 12V should be on pin 4 of the Maf sensors. I suspect this may be disappearing leading to the maf sensors not being seen by the diagnostic equipment. The only thing I see against this is the air intake sensor is incorporated into the MAF and I have not been made aware of an error with this.

Expert:  Mike replied 4 years ago.
Hello again John - Thank you for your reply.

The RP light / message - will only come on, when the Pcm ( engine management computer) detects a "fault" wherever that may be in the systems - so , it wont come come for no reason - If its on, there is a fault that needs to be found / fixed - Once fixed, the message will not come on at all again...

Its always difficult re the wiring - Im not saying its a "broken" wire - if it were , you would have a perm fault - but what happens is the wires corrode inside the loom - causing bad circuits - sometimes it works , sometimes not - movement yes can affect it but its not a given...

If the fault codes you keep getting relate to a given circuit, then it will be either the component in question ie, the MAf ( and as you say, the IA sensor is incorporated in that .) ... , the wiring, / connections to the components - or at the source, the Pcm as I went through above -

Check carefully the wiring to the Mafs as well - peel the rubber boot cover back off the plug - it has been known for the wires where the connect to the pins to break - or, the pins corrode / or push back when connected thus not connecting properly - intermittently.. I would have thought they would have checked those things already - but I mention it just in case..

Other than that - the problem wil be found working through as I mentioned John...

Kind Rgds - MIKE.

.................Please do click on the "OK/ Excellent" ratings for me as that's how Im credited for helping you - Thank you in advance for doing that...

You can and are most welcome to get back to me anytime you might need - clicking the OK ratings does not close you out at all..

Rgds, MIKE.