I have been having a bear of a time with my '97XK8 CONVERTIBLE. This phenomenon 1st manifested last November, a week after I had it Rust Check undersprayed. I went to start the car early one morning (it lives in a heated garage,-- can we say over -indulged??), it started readily enough, cut out on a few cylinders and died. The info center presented me with a Stability system failure, a gear box fault and an engine fault. Eventually I changed the battery, cancelled the fault codes and budda boom, budda bing it started and ran like a top. However since then, every couple of weeks I have had a repeat of the same scenario. I charge the battery, cancel the fault codes and it will run. Until yesterday.I have load tested the battery, and it checks out ok. I even installed a battery maintainer/ trickle charger in the trunk to keep the battery fully charged when I am away. But now I cannot get the fault codes to cancel. My scan tool keeps coming up with different numbers of fault codes every time I try to "Erase". Does this mean it has logged a 'hard code"? I get the same P series codes every time , sometimes 3 sometimes 4, etc. I also cleaned the ground terminals for the trunk, engine bay fuse boxes, and the starter ground strap, all to no avail. Anybody else ever had the same symptoms?

 

It sounds like partially discharged battery has been playing havoc with the electronics.

First fully charge your battery.

Then try a hard reset by removing the negative battery terminal and touching it to the positive teminal for a few seconds. Then reconnect the negative terminal.

Now try to clear the codes.

Then keep the battery maintainer on the battery and see if the situation stabilizes. If it does, you then may just have to trace where you parasitic drain is coming from.

 

I did a static current draw test and it only draws 52illips which is in spec. I like the idea of a hard reset but nervous about any damage that could entail? Have you ever done this ?

 

Sorry my reply should have read 52milliamps. Blasted i-phone keypads struck again. I need to proofread before I send again.

 

Yes, to clarify, you are removing a battery terminal from the battery, you ARE NOT SHORTING the battery.

You will need to reset your windows afterwards. On most US cars you will not need to reenter the radio code.

 

maybe you should check your alternator also, because it sounds like the battery is not properly charging when you run it. Ive changed all of the tensioners, transmission, fuel pump, power steering pump, alternator battery, cam shaft , engine wiring harness, and finally my technician is saying hey your car runs like a champ. go figure

 

why are these xk8's so bad at holding there value. in the blue book its like really cheap to buy these cars. even when you change all of the service bulletins. I guess beauty is in the eyes of the beholder

 

ok I found my problem- it was and still is a contact issue on EM010 at the ECM. It shuts down the throttle body motor, throwing a p1229, and a p1242 code. Also the information centre on the dash will show 'engine fault", 'stability control failure' and sometimes a CAN code p1643. according to JTIS code definitions, both the P1229 and P1242 are linked to stability control and ABS inhibition. Hence the dash warning. I now need to figure out how to keep consistent contact on the multi plug to the ECM. It's the one closest to the engine on a LHD model, probably on a RHD , closest to the fender(wing) panel. Once I messed around with plug and re-connected, low and behold, the TBM started humming and now I realise that this is a good sound when you put the key in the ignition. Thank you for all the advice on the charging system, it definitely helps as British vehicles have quite a well deserved reputation for poor electrics.

 

Do you lock the vehicle and set the security system in this pampered environment?

If you leave it unlocked or even worse leave the key in the ignition, it prevents the electronics going into 'sleep' mode and drains the battery.

Graham

 

It turned out to be the dreaded XK8 Throttle Body Motor failing. I eventually replaced it with a new one and voila' it runs like a perfectly behaved kitty cat. unfortunately I had to buy a new unit, complete with all the old flaws in it so it will not last forever, and will most likely do the same thing again as it ages. For those lucky individual with VINs from 031303 onwards, there is good news. They can be rebuilt. BBA REMAN not only rebuild the units but als re-engineer the flaws out of then units. They have a good solid reputation and have a 2 or 3 day turn around. Check out their website at www.bba reman they have a last of symptons and also various other Jag related electronic issues they can repair. I hope eventually they can repair the earlier throttle body units as they are prone to failure but I guess we will have to wait and see...

 

Glad you got it sorted out and thanks for the follow-up on the resolution.

 

Pleased to hear you've got this fixed. I've added 'RESOLVED' to your thread title to help anyone searching for advice on this issue in future.

The link in you post doesn't work. Is this the place?

BBA reman. ABS, ecu's, throttle bodies, air mass meters, and catalytic converters

Graham