Towbar / Parking Sensor Problem

[topgixer]

Just had a detachable towbar fitted to my ML350 (W164) and now, without anything connected to the towbar, my parking sensors come on full (2 red lights on either side) every time I press the brake. The parking sensors then automatically switch themselves off.

The guy who fitted the towbar doesn't seem to know what the problem is - says what he did wouldn't have effected the parking sensors in any way. Seems a bit of a coincidence it happed straight after having the towbar fitted though!!!

Any ideas? Your help would be very much appreciated!

Many thanks

Dave

 

[GSMGuy]

If the socket protrudes into being "visible" then it will be detected by the sensors...

Had this prob with a detachable on our Galaxy a few years back - On our XC90, the factory fit detachable has an RF proximity chip in the towball part, that "tells" the ECU it is fitted, it then reduces the sensitivity on the central sensor.. Works perfectly, but I believe the "towing pack" was a £2k option as it comes with engine oil and transmission fluid coolers...

Mike

 

[Diesel Benz]

I assume this is about MB OEM parktronic. Do the two red lights only come on or all yellow and the two red?

Does this only happen when braking? Also at higher speed where parktronic should not come on or is it at lower speed when they should not come on (no objects) but do when braking?

If they come on when braking, it sounds like a wiring issue. Otherwise if they just indicate an object near by, then it could be the tow bar parts.

 

[topgixer]

Many thanks for your replies.

It is the MB OEM parktronic I have. It's only the red lights that come on (with the audible sound) and they only come on at low speed in forward and and reverse, when they'd normally be active anyway - and when I'm braking - they come on after having my foot on the break for about 2 seconds.

The sockets are under the bumper and set back a little so I'd be surprised if they are getting in the way of the sensors.

It's a Witter detachable towbar.

 

[whitenemesis]

I didn't think the rears were active until reverse is selected.

If the two red leds light without any amber I would suggest you have a fault. Did the fitter connect into the rear SAM for the towbar electrics or cut into the lighting loom?

 

[Druk]

I have an OEM retractable towbar and the rear sensors sound off momentarily when reverse is selected but only when the trailer electrics are not coupled. The rear sam knows when a trailer is 'on' and disables the sensors. Maybe you need the sam configured?

 

[bouncer]

Did they guy who fitted the electrics use smart relays or the dedicated electric kit with a module. Even with a dedicated module it still needs to go to the dealer for a recode.

sTeVe

 

[richard]

I imagine he removed the rear bumper to install the towbar, so he could have loosened a connector, - but as it happens when you brake (i.e rear brake lights coming on) it is possible he used the earthing point of the rear lights / parktronic for the towbar wiring and didnt tighthen it up properly.

Two red lights on parktronic means an error detected by the parktronic.

It broke whilst he had it & you paid him to completely install it, he needs to fix it !

One other point, certainly on A/B class and my wife's X5 theres quite a lot of upgrades that happen when the towbar is factory fitted (including bigger radiator, and on X5 as well as cooling, theres different rear springs and I think a bigger oil cooler) in order to get the towing load stated in the manual - so just be aware you may not be able to tow as much as the book says without knackering things ...

Richard

 

[richard]

Just checked EPCnet, and yes there is at least a different radiator/blower fitted when the towbar is factory fitted. (some of it is fitted when offroad package is installed)

**edit** to some but not all models to make life complicated **

Also, if using Merc parts for the towbar electrics, theres a wiring loom, fuse and a control unit that need to be installed

R

 

[topgixer]

Guy who fitted the towbar came back today and checked that the sensors were all connected ok. It appears he used Ryder relays. So does it look like I'm in need of a recode?

Thanks for your advice Richard - I'm not planning to get near the quoted towing load so hopfully I'll be ok with what I've got.

 

[topgixer]

Thanks to all that contributed - turned out to be a problem with the wiring - all sorted now.