CL203 Rear parking sensors not working

[440magnumrt]

Searched the forums, but can't find my symptoms.

2005 C Class Coupe. Front parking sensors work fine, but rears have stopped working. No beeps or warnings, but the rear display doesn't light up when in reverse. All 4 rear sensors are 'ticking' if you put your ear against them, which I believe shows they are all working. Reverse lights come on too.

My OBDII scanner doesn't report any faults. Is there anything else I can check before succumbing to a Star diagnostic?

Thanks in advance.

 

[Adamki83]

Searched the forums, but can't find my symptoms.

2005 C Class Coupe. Front parking sensors work fine, but rears have stopped working. No beeps or warnings, but the rear display doesn't light up when in reverse. All 4 rear sensors are 'ticking' if you put your ear against them, which I believe shows they are all working. Reverse lights come on too.

My OBDII scanner doesn't report any faults. Is there anything else I can check before succumbing to a Star diagnostic?

Thanks in advance.

Are they the PDC ones? They light up as you get closer with the red LED’s too??

 

[440magnumrt]

It looks like an electro fluorescent display. Not the later LED type.

 

[Adamki83]

Ahh I see, Mine are the LED ones, but I had an issue when I hit a deer (only cracked a bumper believe it or not) it pushed the 2 of the sensors back ever so slightly and kind of moved them off centre by a tiny amount but this caused them to go haywire eventually you’d get 2 red leds on the dash to show there’s a problem with them. Replaced the bumper that came with the sensors and the problem went away.
So maybe check that the sensor hasn’t fallen down slightly or has gone off centre.

 

[bembo449]

Is there anything else not working ?? Possible SAM issue is what im thinking

 

[440magnumrt]

Thank you both.

All of the rear sensors are ticking when in reverse, so I assume the problem is elsewhere. No damage or dirt on any of the sensors front or rear.

Main PDC unit (and fuse) must be working because the front sensors and display work fine. No other electrical faults either.

I read somewhere that if there's a sensor fault the display will light up, beep and then shutdown to prevent damage. But the rear display never lights up, so maybe there's a fault with it, or the feed to it.

 

[John Laidlaw]

haven't waxed your car recently have you?

 

[440magnumrt]

No! It's actually my partner's car, and the concept of waxing a car would be completely alien to her. I do wash it occasionally though, when I need Brownie points

 

[440magnumrt]

It looks like an electro fluorescent display. Not the later LED type.

This is the front one obviously.