Fail safe mode after hot start

[700SN]

Hi I’m new..just bought a V8 supercharged today. Perfect 4 hr drive home. Parked up on drive then went to start up after 5 mins, foot slipped on to accelerator and revved it up in parking gear, it said fail safe mode. After that I could not accelerate at all so I just moved her back on drive.
Surely I don’t have to take her in to a garage because of that?
She just got serviced too and as a precaution I double checked oil and fluids and all are still topped up.
Does anyone know if perhaps the revving in park caused a temporary lock on the fail safe?
Do you think it is a temporary issue and will be ok in the morning?
Otherwise I’ll have to book in a code reader at my local garage which is a pain seeing I’ve only had her about 7 hours!

Help most appreciated!
Cheers
Stuart

[steve_m]

Can't help you on the failsafe mode I am afraid but welcome to Jag ownership!

[Andy P]

Hi Stuart and welcome to the JEC Forums.
Sorry to hear about your problem after such a short time.
First thing I'd do would be a hard reset.
That means take the negative cable off the battery and hold it on to the positive terminal for about 30 sec.
Have an accomplice turn the ignition key to aux 2,this should drain the cars modules.
Then re-connect battery and see if the car has gone back to normal.
Good luck.Let us know how you get on.
Andy

[700SN]

Appreciate that Andy, will do it probably at the garage, just to make sure I don’t spark it and mess anything knowing me.. where is the ECU located, in the boot next to the battery? Cheers

[Andy P]

No,the ECU is located under the plastic panel next to the coolant reservoir under the bonnet on the passenger side.
I take it your in the UK,if your not then the driver side.
Here's a couple of photo's of the hard re-set.

If you would like a workshop here's a link to mine:
https://drive.google.com/file/d/1eBYqxQ ... sp=sharing
Feel free to download and keep.
Take care and good luck.
Andy

[700SN]

Thanks Andy, much appreciated! She’s running fine now, luckily I know my local garage well and was diagnosed with a poorly performing TPS, reading just 7% on the code reader. However I suggested the hard reset as you described and despite him saying in jest that it normally doesn’t work, it solved the issue...

The lesson learned from that, is never to rev hard (or maybe never at all) when in park position, I suspect the module senses something not right and protects the gearbox/engine accordingly. So all good!!

Cheers !!

[J44EAG]

Also check the two small 3mm OD rubber pipes, one coming off the SC pressure stub pipe and also the one below the throttle body. Both link to the bypass actuator. These two pipes rot and split with age. Any air leakage with throw fault codes. Halfords sell a quality replacement pipe that is thicker walled than the OE Jaguar equivalent. Its also cheaper too! You will need about a metre of it. Replace as preventative maintenance. Well worth doing.

Mike K

[Andy P]

Hi Stuart,
Glad you got it sorted easily.
The hard re-set is always a good place to start especially with sensor issues.
It's easy to do as well and if it does not work then we have to look a bit deeper using the code reader.
Take up Mikes advice,he knows his way around the super charged engine and is very knowledgeable where they are concerned.
I've not had a super charged one yet and I emphasize the yet bit,that time will come I'm sure .
Enjoy your car Stuart, happy and safe motoring.
Tell us what year it is and post a couple of photo's so we can all enjoy.
Take care.
Andy.

[davidr]

There is a protective mode in the ecu that prevents the engined beings over-revved out of gear. It cuts in at 3000 revs I think. I also doubt this would have provoked your problem in itself but if the TPS is suspect that could explain it.

[J44EAG]

TPS sensor tracks do wear but usually only after quite a fair mileage has been accumulated.

The MAP sensor is also known to clog with oily grunge. This lives in the elbow below the throttle body and the charger. They can be quite a job to extract due to hardened crud. The sensor seals via an o-ring which can coke up and make extraction difficult if the elbow is still on the car. The sensor can be cleaned in carb cleaner and can be a filthy job. Much easier with the throttle body off the elbow which makes more space. Again the throttle throat can fill with grunge. Every bit of it has to be removed. That is a separate subject in itself. Get a new gasket from a Main Dealer BEFORE you start any clean up. All these clean up and other preventative measures help reduce the tendancy for issues to develop. Eventually you work your way through them all.

See my thread on V8R throttle area maintenance and the subject thread which is tuning the SC V8 for more grunt!viewtopic.php?f=281&t=10761&hilit=tuning+v8

Mike

[700SN]

That’s very impressive Mike and thanks for your help. In fact I’m sorry to say, failsafe happened again today after just a short journey.
I did the hard reset after an embarrassing limp home.however it didn’t seem to work properly like last time. Instead the engine light remained on amber. Did seem to drive ok though but I only went a few hundred yards.
As she’s still under warranty I’m going to book her in for a swap out of the TPS. That’s what the garage code reader came up with. Whilst there I’ll inform about the pipes..
soooooo annoying, only done 3 trips in her and it s like I’m not enjoying it.
I’ll see what happens tomorrow morning, garage is really busy but will try to fit her in

Would anyone know the exact part number for the TPS? (XJR V8 4.0 SC, 2001) and I need the gasket too, right?
Not sure how to post a pic on here yet I tried “img “ but it never points to any pics on my device.

Cheers, Stuart

[Andy P]

Hi Stuart.
Sorry to hear your still having problems my friend.
The TPS unit is not sold separately by Jaguar you have to buy the whole throttle body .
The OEM Part No is 198500 3250

TPS X308

But if it is the TPS that is faulty then DCR AutoParts has new ones listed.Not sure how much though.
Here's the link:

https://www.xk8-parts.com/2020/04/air-a ... lery-page/

I would get the garage to check for any codes before doing anything but they should do that anyway.
To add a photo click on Attachments and then click Add files,the file should open up then.
Good luck with it all anyway.
Take care.
Andy

[700SN]

hi Andy / all, that's really appreciated, thanks!
i fired her up fist thing and well, no warnings/fault codes. So --
i went down to my local garage who agreed to do another system diagnostic check at very short notice. I kept her running whilst he did it, and came up "P1222 Pedal demand sensor B circuit low input"
so he said it would definately need a new TPS - i said ok i will do a search myself rather than rely on euro-car-parts or whatever...

Being new i started at the front of the current JEC magazine and looked up suppliers one by one for this part, none could find it, apart from two, who kindly stated they only do the entire throttle body, which is absolutely absurd for something which costs diddly-squat to produce.
-- so after 2 hours of web searching and 'phone calls I tried ebay, MRA in Glasgow had one and i called him to check. (https://www.ebay.co.uk/itm/353100729974) it seems alot cheaper than DCR too. The OEM matches the one on mine too 198500 3250. so i did "buy it now"..just over 36 quid free delivery.

Would I need a gasket separately? if so, i am tempted to ask a part number, but if Jaguar did not sell this separately not sure?

i also could not find anything on the halfords website for the pipes J44EAG mentioned, "small 3mm OD rubber pipes, one coming off the SC pressure stub pipe and also the one below the throttle body. Both link to the bypass actuator. These two pipes rot and split with age"
it would be good for a link for those too? i don't want to get just any old 1/8" pipe.

although she's under warranty, I may contemplate doing the swap-out myself, i can see it would need the air flow/filter ram pipe taking off to get to it, maybe simple job? is that all i need to do, in order to then just well, presume, unscrew / unplug the old TPS and replace it?

appreciate all the help on this, after that limp home mode for 7 miles at 5mph with what was my 18 year old daughter's first trip in the passenger seat, (not a very cool driving experience at all!) i just really need to be able to at least be confident to start driving my new purchase!

cheers
Stuart

[J44EAG]

The Halfords pipes are generic stock which will usually be found on one or their point of sale racks.

The Jaguar OE pipe comes in lengths of about a metre. It is of rather a thin wall design and rots and splits for a past time. The Halfords product is from after-market sources and is somewhat thicker and more robust than the Jaguar product. In my opinion it is certainly more robust than the Jaguar OE product.

At the end of the day, the choice remain yours. I`d go for the Halfords product every time.

Mike

[700SN]

hi Mike, agree - i just cannot find it on Halfords website. I cannot see any 1/8" OD pipe anywhere else - the minimum ID is 1/10 or 1/8 making the OD about 1/4 at the minimum. i will keep trying for that & the gasket.
cheers