stiles_s

Hey, I installed wheel arch extensions and some 5mm spacers last week. Love the look.

But, LCA (lane change assist) is no longer functioning.

I took my time and was careful. But, I read in another thread that the LCA sensors are behind the rear bumper? Anybody have any theories for how I might have messed with LCA while doing this job? I had the rear wheel liners out in order to do the wheel arch extensions. Maybe I unplugged something? Theories?

Thanks all,

Scott.

PS. 2016 Cayennne S w/air & pasm in case that matters.

deilenberger

Eilenberger's Law of Troubleshooting "Look where you last worked"..

I foresee the wheel arch liners coming out again so you can see what got disconnected.

stiles_s

Thanks. Can anyone confirm that the Lane Change Assist sensors are behind the rear wheels in the rear bumper?

chiapet15

I have a Cayenne S ehybrid and removed the bumper this past weekend to install an aftermarket trailer hitch. Attached is a pic with the bumper removed. If you look carefully, you can see a bright green connector and a black connector just above the leftmost exhaust tip. Those connectors interface with the rear fog lights and the proximity sensors in the bumper. While the wiring harness does go behind the wheel well area, if you only pulled off the wheel arch extensions, it's hard to believe that you affected the wiring harness at all. You can also see in the pic where the wheel arch is dangling on the left right next to those aforementioned connectors. After i put everything back, the first thing I tested were the parking sensors, LCA, and rear fog lights, and thankfully everything was still working

stiles_s

thank you! I did pull the wheel well liner to replace the whee arch moulding. Maybe I disturbed something while I was in there.

My rear parking sensor still works.

where do the proximity sensors mount?

Philip Goughary

In the previous picture, the proximity sensors are the black rectangular plastic pads about a food up from the exhaust tips. They have an aluminum hosting as a base and black plastic wiring harnesses plugged into their sides on the outsides.

chiapet15

i couldn't find any details about the proximity sensors in the alldatadiy repair manual that I reference for this car (they only go up to the 2014 hybrid, which is mostly the same and serves its purpose for doing maintenance work)

To me, it seems that the round plugs in the bumper are the transmitter and metal boxes with plastic covers are the receiving antenna that measure the doppler effect. Based on this, if your parking sensors work, the hardware for the LCA should be fine and properly connected. The only things i can think of are desensitization of the sensors, where only LCA wouldn't work, but parking sensors would due to the higher strength of those reflections.

Can you take this to the dealer to have them look at it? I really don't think the harnesses and connectors are so fragile that removing things as soft as the wheel arch extensions or the wheel well covers would break them.

stiles_s

Thanks everyone. I'll pull the wheel and maybe the liner off to see if I disturbed anything obvious, but I agree that a trip to the dealer is probably in order.

deilenberger

No - two entirely different systems working on different spectrums of energy.

Parking distance sensors are ultrasonic - they buzz at a frequency you can't hear - and listen for the reflection. The LCA is done with radar - ie - radio waves. High enough frequency that it sets off radar-detectors on following vehicles.

One is auto, one is radio. Different animals.

wkearney99

What was the end result?

I ask because my '17 has a very slight pull to the left but only at speeds of 80+ on the highway. When I inquired about getting an alignment check I was told that since I have LCA it'd require more shop time to set up all the testing gear.

deilenberger

Are they kidding? I can't see ANY correlation between LCA and wheel alignment.

wkearney99

They haven't blown smoke yet, so I don't have much reason to distrust them... Still, it might merit a call to another dealer or Porsche for a second opinion.

r553

I've had a wheel alignment several months ago and there was no mention of LCA interaction with the alignment. The head mechanic at our local dealer said they have to do an LCA calibration if the rear bumper cover is removed.

I vote for Don's theory of inspecting the scene of your last work on the car.

wkearney99

It's new last Winter, so there's been no 'last scene' to check. Interesting to hear your alignment had no LCA involvement. Were the bumper involved, yeah, that'd make sense. I've yet to check alternative dealers in the area.

stiles_s

I get to fess up to one of those moments where I was convinced I knew what caused something and I was totally wrong.

Just random luck that it stopped when I did the wheel arch extensions.

My wife drove the cayenne and tapped the Lca button and turned it off when adjusting the mirrors. So, that was it 😀

Credit to the dealer for not calling me an idiot to my face. I am sure there were stories later.