Technical Forward Collision Warning with Active Braking

[VeneziaBlue500x]

My 500X has the "Forward Collision Warning with Active Braking" feature, which is a wonderful technology. One day, it decided to stop working and produced three different OBD codes. The dealer told me that they require several days to diagnose the problem and to perform a re-calibration with a special tool.

So I went to a friend mechanic, who told me to just replace the rear cluster bulbs. Indeed, I found two of them to be blackened, replaced them and lo and behold, Forward Collision started working again, all error codes cleared immediately.

I just wanted to share my experience, in case you hear the same excuses from your own dealer

 

[The Panda Nut]

My Panda has CBC so I am very interested in your experience and thank you for posting.

 

[Ralf S.]

Rear bulbs fixes the collision avoidance doodah.... What new weirdness is this...?


Ralf S.

 

[s130]

A possible explanation is this, which also begs the question how the bulb failure detection works in this case.

On my 500X 2015 Cross Plus (and I see no reason why any other bulb 500X would differ) the side lights and brake lights are actually two bulbs wired in parallel. When side lights on the bulbs are only fed with a reduced / modulated voltage. When the brake is pressed they get the full 12V/100% modulation thus glowing more brightly.

When I fitted my tow bar I got confused as well because there are two wires which indicated one fed the side lights and one the brake lights. I did not inspect the internal wiring of the light cluster. So I wired the bypass relay wires to each side of the car. I then tested, before putting all the car trim back, that when I turned the side lights on the trailer lights came on. Then pressing the brake pedal the trailer brake lights came on as well. Brilliant, job done.

Later I found out looking in my mirrors that with side lights of and then pressing the brake pedal the trailer side lights illuminated as well as it's brake lights!

Having check technically / legally / MOT this is not problem. I could fix by snipping one wire but decided to leave asis as now when I brake the caravan's rear red side lights and top front read rear corner lights come on together with the brake lights. So I have maximum RED possible so nobody can say they did not see my brake lights

 

[cowabunga]

I have had error messages for this in the past, and whenever it occurs it always seems to be when driving in very heavy rain. When the rain stops the problem goes away.

 

[Romirez]

Rear bulbs fixes the collision avoidance doodah.... What new weirdness is this...?


Ralf S.

Hi, I used to have a Jeep Renegade with the same FCW system, I had a issue with the FCW not working kept apperaring, the only way it went away was when the ignition was switched off and on. The Jeep dealer after several trips found it was the Led brake and rear light bulbs that caused the error. They replaced them with the original non Led bulbs and the problems were solved. I bought a 2016 Fiat 500x, it had the same fault, I took off the rear lights and found the P21W bulbs has slightly blackened. These where replace new P21W bulbs from Halfords and yes ther error message went away completely. So before you go off to the dealer, just check and replace the rear bulbs