GL450 trailer hitch installation
Junior Member
Joined: Sep 2007
Posts: 50
Likes: 0
BMW
On the 2010 model the rear sam will have two plugs in the rear corner for the hitch if they are there you should be good. I plugged mine in and set the other plugs up and plugged in a hitch and try to raise the shocks if it works you need a program, if it tells you that it can not be raised you are good.
Last edited by jh87; May 4, 2011 at 12:47 PM.
Senior Member
Joined: Aug 2003
Posts: 288
Likes: 2
I just went out to look at mine red wire goes to power, brown is ground, one black plug to sam. The only one left is the green plug and thats for the trailer break if you add one, but just get a wireless one for a little more money. Test it on a trailer and try to raise the truck with the trailer connected it should tell you it cannot be raised then you know it will all work.
Junior Member
Joined: Sep 2007
Posts: 50
Likes: 0
BMW
That is what I was thinking too, thanks for the info. It is good to know there is a wireless one for the trailer break. I only plan to use the hitch for cargo box at this point, but definitely will look into the trailer break control in the future. Thanks again.
Senior Member
Joined: Aug 2003
Posts: 288
Likes: 2
No papers come with it. Get the service guy at dealer to print out a pic of the rear bumper and you will be good. There are 2 bolts for bumper in wheel well, pull carpet in the rear two in the back for rear and two on each side by the side lights. You can just pull the bumper off and set it on the ground without rermoving the parking sensors. It is a easy job when you know where the bolts are. Let me know if you need some pics.
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Senior Member
Joined: Aug 2003
Posts: 288
Likes: 2
Yes they are two cast iron fram supports that bolt in with 2-3 bolts on each side from insidew the trunck area, I think they are the same for the ml, I think thats what my parts guy said. You need these do not install yet as these have to go in first then the hitch bolts to them.
Junior Member
Joined: Jul 2009
Posts: 58
Likes: 4
From: Seattle, WA
2007 GL450
The SAM unit on your '08 450 MAY not need to be changed when the hitch wiring is added. The purpose of getting the car's electronics to 'know' when you are towing is to adjust the settings of the Electronic Stability Program so as to NOT create an unsafe braking situation. Only the SAM can do that. Ask your dealer to find out for you if your SAM will need to be changed - or maybe just reprogrammed. '07s needed to be changed, late '08s did not.
The ESP is supposed to control some stability situations by applying the trailer brakes first. If it doesn't recognize there is a trailer, it can't do that. Be careful what you do, it is possible to create an unsafe situation and not even know you did.
The ESP is supposed to control some stability situations by applying the trailer brakes first. If it doesn't recognize there is a trailer, it can't do that. Be careful what you do, it is possible to create an unsafe situation and not even know you did.
As I understand it, the trailer brake output on the back of the truck is routed to the harness under the dash (or rear compartment on vehicles built in '06) terminating with a green connector. This connector receives its signal from an aftermarket brake controller and routes the braking signal to the trailer connector.
I'm in the process of figuring out exactly what I need to install a brake controller for my 07 GL450 and I'm still not clear on why the SAM needs to be replaced. My truck provides indication of trailer light status when I have a burnt out light and prevents the high suspension setting so I know the current SAM recognizes when a trailer is connected.
What additional function would an updated SAM provide when using a trailer brake controller?
Super Member
Joined: Feb 2009
Posts: 711
Likes: 11
From: NW corner of CONUS
2008 GL 320 CDI, 2004 VW V10 Touareg TDI
"I neither understand what I know, nor do I know what I understand; but I do know that the more I now know, the less I understand!"
Clearly, surge brakes cannot be compensated by the ESP program since it has no 'knowledge' of when they actually apply. Likewise, the ONLY way the ESP even has a chance of creating stability (absent a pretty exact knowledge of the mass of the trailer) is it's measurement of the towing vehicle yaw rate characteristics under actual stability conditions. According to the sales books I read at the time I bought my GL, the ESP program takes these into account in 'deciding' what to do under pending skid conditions. It is only logical, that, since the SAM unit 'knows' the trailer is there, and has brakes, that it apply those brakes first. Any trucker will tell you of the surprise if he sees his trailer coming 'round to meet the front of his truck - thus he always hits the trailer brakes first. I have never had the 'luck' to push the MB system to it's limits and check it out!
Clearly, surge brakes cannot be compensated by the ESP program since it has no 'knowledge' of when they actually apply. Likewise, the ONLY way the ESP even has a chance of creating stability (absent a pretty exact knowledge of the mass of the trailer) is it's measurement of the towing vehicle yaw rate characteristics under actual stability conditions. According to the sales books I read at the time I bought my GL, the ESP program takes these into account in 'deciding' what to do under pending skid conditions. It is only logical, that, since the SAM unit 'knows' the trailer is there, and has brakes, that it apply those brakes first. Any trucker will tell you of the surprise if he sees his trailer coming 'round to meet the front of his truck - thus he always hits the trailer brakes first. I have never had the 'luck' to push the MB system to it's limits and check it out!
Last edited by Fourdiesel; Aug 15, 2011 at 06:23 PM.
Senior Member
Joined: Feb 2010
Posts: 331
Likes: 3
2011 GL350 Bluetec, Irridium over Black Leather
Most of those units are inertial - they look for two things: 1) an active brake light circuit, and 2) an inertial measurement of the tow vehicle slowing down.
The SAM is not in the actual brake activation circuit - it's only in the brake light circuit. The brake controller (Tekonsha Prodigy RF, in my case) is what actually applies current to the brake circuit.
What the SAM is most likely doing is braking one or the other of the tow vehicle rear wheels to counteract yaw.
- Mark
Junior Member
Joined: Mar 2011
Posts: 35
Likes: 1
From: WA
2007 MB GL450
Today, I got the tow hitch from LKQ auto parts from a 2007 GL450 and that's the one I have as well.
This was everything that came with it. Heavy duty beam for each side, including wiring. I thought it was going to be different, since on other peoples' posts I did not see exact one and the extra parts. Questions...
1. Anyone have ideas on the extra items?
2. Do I need to disconnect battery when connecting to rear SAM? (Per dealer's checking VIN, I was told that I did not need new SAM. It does have a spare plug space).
3. Are there detailed instructions, with illustrations?
4. When I take the bumper off, do I need to disable the sensors? I want to make sure that nothing gets messed up. Thank you!
5. One of the wires is ground, another plug goes to rear SAM and two fuses. I am not sure what slots the fuses go into go into? There are many different colors.
This was everything that came with it. Heavy duty beam for each side, including wiring. I thought it was going to be different, since on other peoples' posts I did not see exact one and the extra parts. Questions...
1. Anyone have ideas on the extra items?
2. Do I need to disconnect battery when connecting to rear SAM? (Per dealer's checking VIN, I was told that I did not need new SAM. It does have a spare plug space).
3. Are there detailed instructions, with illustrations?
4. When I take the bumper off, do I need to disable the sensors? I want to make sure that nothing gets messed up. Thank you!
5. One of the wires is ground, another plug goes to rear SAM and two fuses. I am not sure what slots the fuses go into go into? There are many different colors.
Newbie
Joined: Sep 2012
Posts: 7
Likes: 0
2008 GL450
2008 GL 450 TRAILER HITCH
I’m trying to order hitch kit for my 2008 gl450 just got all parts number from getmercedesparts.com with trailer hitch & cable kit it came out close To $665 . but Do I also need to buy lower shield ? IT’S another $ 330 for the parts. Also where exactly SAM s located so I can hook up the wire . Thanks
Senior Member
Joined: Aug 2003
Posts: 288
Likes: 2
I cut mine out like many others with a dremal when you take the sheild off flip it over and you will see the line where it needs to be cut, easy! Sam is in the rear right corner below fuses. If you need to know where to plug into let me know and I will look ar mine. Also when you guys drop the bumper you can leave it on the ground with the rear wires hooked up. Not a bad job but it looks like the price went down on them as I paid 950.00 from the same place in 2010.
Newbie
Joined: Sep 2012
Posts: 1
Likes: 0
07 GL450
needs help.......
just purchased a trailer hitch from stealership..... planning to install myself coz the dealership charging me almost $ 600. But when I opened the box, no diagrams nor instructions..... any assistance (diagrams/steps/instructions) wil be greatly appreciated as I'm stuck trying to get the rear bumper out...... its 01:00 and hardly even moved the bumper..... thanks
Newbie
Joined: Sep 2012
Posts: 7
Likes: 0
2008 GL450
2008 GL 450 TRAILER HITCH
I cut mine out like many others with a dremal when you take the sheild off flip it over and you will see the line where it needs to be cut, easy! Sam is in the rear right corner below fuses. If you need to know where to plug into let me know and I will look ar mine. Also when you guys drop the bumper you can leave it on the ground with the rear wires hooked up. Not a bad job but it looks like the price went down on them as I paid 950.00 from the same place in 2010.
Yea it will be much helpful if you let me know where the plug goes to. Since the cable kit don’t come with any instructions.
Senior Member
Joined: Aug 2003
Posts: 288
Likes: 2
The bumper has a few 10mm nuts the one are inside wheel well behind the plastic just pull it out to get to them also the ones you have to get from inside the trunk area above the ablue tank. I will check my plugs and let you know where they go
Newbie
Joined: Sep 2012
Posts: 10
Likes: 0
From: Chicago IL
07 MB GL320 CDI
I have just ordered a compete hitch from a salvage yard. One extra thing they are willing to send me is the SAM module if I can only tell them where it's located, how it looks and where it plugs into. Can someone provide me with that info please? Also, will it work if I plug it into the same make model and year or there is no way around buying a new one from the dealer and having it programmed.
Member
Joined: May 2013
Posts: 86
Likes: 8
From: Houston, TX
'98 E320 and '08 GL320
Can anyone give me the details about the electrical connections? I connected the trailer harness to the SAM, put brown to ground, and ran the red up to the fuse panel, left the green connection for a future brake controller--where do the extra relay and fuses that came with the hitch go, and where specifically does the red connect?
thanks in advance!
thanks in advance!
