So today I put a new battery in the old 97 XJ6 and the car started up instantly and ran great. The car had been sitting since October. After 2 hours the car died on me and would not restart. I left it on a side street and went back to it after a couple of hours. It started after several cranks. I was getting only code P0727.

I was able to drive 2 blocks in limp-home mode and the car died again. This time while cranking I noticed the tach needle would sometimes jump up from 0 a little bit and sometimes would not jump at all (just remained at zero). After another wait of 2 hours the car started died again and would not start after just 200 metres.

I'm suspecting the crank position sensor or wiring thereto is faulty. Any other suggestions from the experts on what else I should look at before spending a couple of hundred bucks on a new sensor? The existing sensor, the one I'm suspecting has failed, was installed only 5 years ago.

 

JTIS does not show code 727 for an X-300. but the generic Jaguar P0727 is engine speed circuit. So, between that and no tach, it would be a pretty good guess your CKPS has failed, assuming it is plugged in properly.

 

It's a transmission code. I just looked in my X300 ROM. Too hot to do anything and I was curious .

It appears, in essence, that P0727 will set if engine rpm drops below 95 rpm while the transmission speed sensor shows above 300 rpm. In other words the engine conked out while the car was moving.

My money is on the crank sensor as well....although Sparkenzap's remarks certainly don't need backing up from me.

It seems to me that if the crank sensor is replaced but the harness isn't tied back adequately the wires could foul against one of the v-belts. Just something to think about since the sensor was previously replaced

Cheers
DD

 

Well I just went out to the car again after it has cooled down and still no start and no movement of the tach needle. Tomorrow will be a day to inspect and test the wiring and then, if necessary, order a new crank sensor.

Thanks all for backing up my suspicions and making me feel better about having to order a new sensor.

 

Replaced the crank sensor today and the car started instantly.

The exposed metal tip of the old sensor was covered in rust. A cleaning may have cured the problem but I chose to install the new sensor. The car is running perfectly.