Sent Gendan an email about theiir elm327, got this reply

Hi,

Thanks for your email.
Yes, our ELM327 interfaces should work fine on a 1999 4 litre S-Type, and we have actually tested some of them on a 1999 3 litre S-Type, which also uses PWM.

Best regards,

Mike West
Specialists in Car Diagnostic Tools
Gendan Limited
http://www.gendan.co.uk
Tel: +44 (0)1792 588002
Fax: +44 (0)1792 588233

it's £45, will get one as soon as i have some money !!!

 

I'm trying to figger out why you guys are having so much trouble getting your Elm327 devices to connect to your Jaguars. As I mentioned in a post elsewhere, I use the two below daily, one USB and the other Bluetooth. I have not found a Jag yet that I CANNOT connect to, with either one.
It has just got to be the Chinese knock-offs. I steer clear of them.

Good luck guys!

 

the one from genden (the genuine elm) has a box that the two cables connect to like yours, USB and obd dlc, the one i got from hong kong is all in one.

ELM327 Scanner Software USB Interface - Free Shipping

 

On the basis that it's a non-working elm327 clone, that's why.

(If it turns out to be a problem with the PWM pins/wiring then the guess about the elm327 was wrong LOL)