How many sensors are on the XF. AA guy tells me they are only on nearside front/rear but I would have thought it would be one on each wheel.

 

 

Thanks.

I assume I need to remove calipers to replace sensors?

 

i think you could manage to replace the sensor without removing the caliper, but why? if your sensor is tripped, need to replace brake pads so the caliper needs to come off anyway. if i recall correctly it will be crusted in there pretty good amidst brake dust and such so it's a great time to clean it up a bit.

 

No need to remove the caliper to replace the front sensor, it simply clips in to a slot on the top of the pad through a gap in the caliper.
But be very careful and make sure you go in at exactly 180 degrees to the pad otherwise you are bound to break the sensor clip off, it is extremely brittle.
You need to remove the inner pad to replace the rear sensor, which means the rear caliper has to come off.
Why?
Because the rear sensor slots into a spring which fits into the rear pad and you need to remove that spring from the pad, open it up a little (squeeze the ends together with pliers), push the sensor into the spring and replace the spring onto the pad, then as you replace the pad in the caliper feed the sensor wire through the gap in the top of the caliper.

Here's a couple of pics I took of the rear pad and sensor off my old XFR (the cooking XF with the 326 mm rear brakes has different pads but the same set up):

 

I'm getting low brake pad indicator, but visual inspection shows 8-10mm left on all pads so plenty of life left in them. I recently had rear wheel bearings replaced and I suspect the sensor was damaged in the process.