I did a search on this malfunction, and came up with nothing, so here goes.
2009 XJ Portfolio. The adaptive cruise does not "see" the cars ahead of me all the time, likewise the front warning system does not
see objects either. Sometime they both work properly...about 50% of the time.
The cruise will always set to whatever speed..and hold the speed. Just not "seeing" cars, oblects.etc...
Any ideas?
Thanks

 

Hmm, front licence plate installed partially blocking the sensor?

 

Thanks for the reply, no front plate installed. Not required in my state.

 

So I have determined that it is the sensitivity that changes.....I am aware of the gap changing adjustment and it is NOT that.
Is there a way to re aim the radar sending unit for the adaptive cruise and collision avoidance system.
I am convinced that it has moved, where is it located...I assume the front bumper, but can not see it.

 

The Adaptive Cruise Control Module (ACC) is mounted behind the front bumper to the left of the radiator (as viewed from the driver's seat). It is near the air suspension compressor and left fog lamp.

The Workshop Manual has a procedure for leveling the ACC, but you should only do that while the air suspension is properly inflated, and if possible, calibrated using SDD.

It is possible that you have one or more codes logged regarding the ACC - there is at least one DTC that pertains to the module needing to be releveled.

Another possible cause of ACC problems is mud/snow accumulation or other obstruction on the bumper in front of the module.

Cheers,

Don

 

Thank you sir!

 

I should have also mentioned that, given your symptoms, it would be worth cleaning the ACC electrical connector with a good zero-residue electrical contact cleaner spray.

Also clean the ground stud behind the left headlamp, where the ACC is grounded. Note that the torque spec for the aluminum nut on the aluminum stud is just 6.5 ft. lbs., which is just a little tigher than hand tight. Several of our members have learned how easy it is to snap off a threaded stud by overtightening the nut.

Cheers,

Don

 

Fantastic help! I will do all of the above tomorrow, taking extra care with the stud, and post the results.
Thank you!

 

I put the Jag up on the lift and pulled the front gravel try off. I could easily access the ACC radar sending unit from there.
I noticed right away, that the unit looked as if it was facing down toward the ground..about 20 degrees , which did not make sense to me, as the unit needs to see vehicles and objects in front.
I made sure the car was at its normal ride height with all the air suspension at its driving setting.
I then put a level and then a degree meter on the back side (see photos) and set the unit right at level, 90 degrees to the ground. Easily moved the unit by hand.
IT IS FIXED AND WORKING PERFECTLY NOW!
Thank you all for your help, very pleased!

Hope this helps others in the future