Danno, that makes sense,, I guess the current draw is not enough, and It was not explained why the computer needed to be flashed,, what does that mean? thank you for your reply..

 

Reflashing the computer simply means that they insert an updated base program in place of the existing program... The computers these days control nearly everything in the vehicle... The engine and all of its parameters, the transmission and how hard and when it shifts and in the case of Mercedes, nearly all electrical services rely upon the computer for something or another... Its possible that the original programming in the computer was not "talking" with the newly updated SAM properly, which caused the trailer light issue... They reflashed or reprogrammed the main computer to properly interface with the SAM, which seems to have fixed your problem...

On another note, these days there are a lot of trailer lights to choose from... LED lights are a popular option since they are sealed and do not burn out as frequently as standard incandescent bulbs, they also consumer much less energy... Unfortunately, Mercedes in its attempt to help the driver by notifying when there is a burned out bulb will also think there is a burned out trailer light bulb if the trailer that you are towing has LED Stop/Turn/Tail lights.... This is not all bad, since it simply displays a message, but just so you know, if your trailer has LED lights or if you switch to LED lights, you should expect to see this message.

 

Thank you for the very complete explaination,, I do have LED lights on my trailer, so I won't be worried if I see the lights out on the dash. The dealer didn't explain all this to me. I am glad I have trailer lights. I think most service advisors don't know that much about the cars they are working on. Once again,, thank you.

 

Hi everyone........this thread is interesting as I saw most of the mentioned faults.

From memory - the warning lights on your dash re; trailer = IF you hook up a 12v globe to an indicator pin (ie green - pin 3 - RH indicator) whilst you have the RH indicator going the globe will work in sequence with the vehicle flashing its RH indicator light. If whilst doing this (indicator still on) you remove the temp globe and place it onto your LH indicator trailer pin (pin 2 - yellow), then go to change the vehicle to LH indicator you will notice a 'trailer indicator globe XXXX failure" warning on your dash.

As for LEDs and globes on trailers - on our trailer we have led side markers, globe tail/brake/indicator lights, led rear proximity lights, globe front proximity lights, a 12 volt water pump, two 12v globe interiors and a 55 watt flood light on our trailer, electronic brakes powered from the vehicle, electronic back-up trailer brakes charged from the vehicle and it all works as it should - eg it is not confusing the Merc brake controller (SAM).

 

Hi! I'm having the brake controller installed on my GL450 this SAturday. I would appreciate your assistance. Where did you install the brake controller unit. There doesn't seem to have any space for the unit below the dash. I understand that the unit is usally installed at the right side below the dash. If this was so, my knee would bang into the unit.

Thanks in advance

 

Danno4X4,

What model is your GL? I have a 2007 GL and had just installed a hitch by the MB techs. The SAM (green connector I think) is located at the right rear compartment. Was you hitch receiver factory installed and because of this reason the SAM was located at the front? I'm pretty stressed knowing the fact that my SAM is in the rear and knowing that the installers may have to reroute the wires to the front. The Brake controllers will be installed by the Recreational vehicles providers tomorrow.

 

I did have the factory hitch installed... My GL is a 2007 model built in late May 2007. The connector was just above the driver's side footwell just on the other side of the panel. They had moved it from the back up to the front after December 06 builds I believe. In my vehicle, the SAM is still in the rear, but the connector for the trailer brake controller is up in front.

 

For the archives:

I hooked up my Tekonsha Prodigy trailer brake wiring to my 2010 GL350 this evening. As described in an attachment at the beginning of this string, I needed the green plug and 4 pins from the MB dealer.

Specific to the Prodigy wiring:

Prodigy Wire - MB Wire - Pin # on Plug

Black - Red - 4
White - Brown - 1
Red - Black/Red - 3
Blue - Yellow/red - 2

Pretty easy.

 

Tested the trailer with recently installed/wired Prodigy brake controller and all is well. Nice tow vehicle!

Oh and I had the tongue weight of my trailer measured: 430 lbs so I am well under the 600lb limit.

 

Although I have a 2010 ML BlueTec, my wiring question should be the same as a GL:
I wired the X58 green plug to a brake controller pigtail and I checked continuity / ground / power to the plug and everything is OK, except for the red brake signal (thin blk/red from the MB harness). It measures 3.9 V at all times and it doesn't change with brake pedal depressed or not.
According to the 2007 Star bulletin, posted above, this wire is the "Brake light circuit. This is the brake signal for an electric trailer brake controller (input to the electronic brake controller)."
I have the Lighting Package with LED brake lights, and I am thinking that without a real load I will get that reading.
I don't want to fry my wiring, so I am being cautious - and asking if I should fix something before I hook up a brake controller.

 

I installed the brake controller on my 09GL BTC and noticed the same, the brake signal is always 3.x V with or w/o using the brake. Wondering if it's normal or not. anyone can shed a light on this?


!!!!UPDATED!!!!! - Just tested with load, it worked perfectly! GL turns the controller on ONLY when the trailer is hooked up, which makes sense to me since 99% time the truck won't drag a trailer anyway, it would be silly to see that little LED dot on and off w/o a load.

 

Thanks for your response. Out of curiousity, last night I queried JustAnswer.com - a resource that I found Googling for the X58 "green plug" above. I asked the identical question as above. I got a knowledgeable response from a tech, part of our chat is here:

"Diagnostics Engineer: Electronics are constantly monitoring what is the resistance and load connected to black/red wire. When you measure it with tester it shows 3,9V. If smallest resistance- the voltage will drop and electronics will recognaize by this that something is connected to this pin. When nothing is connected- no change will be there.
So connect the trailer brake according instructions. If it does not work right away- version coding with Star DIagnosis computer will be required to activate this pin.

ME : That was what I suspected. But just to confirm, there should be no damage to the car's circuitry - either the brake controller will work or it won't. If it doesn't, then coding the SAM should bring it to life. Correct?

Diagnostics Engineer : If you connect everything according to instructions- worst case scenario will be a blown fuse.
Provided the SAM has a correct part number- only coding will be needed."

This response (cost me $38) and rayleiwu give me a lot more confidence to buy a Controller and start pulling trailers!

I guess I should have just followed Texas993, hooked everything up , skipped the voltage check and I'd be fine.

But, trailer shops and two M-B dealer shops seemed to be afraid to answer my questions, so I was cautious.

 

Great work! I towed quite a bit this summer and noticed that the GL turns off the controller if nothing is plugged in the rear.

The GL also turns off the lane change warning system if a trailer is connected.

 

Forgive me for the simple question, but, can someone tell me the specific location of this plug on the 2010 GL450 (I have the MB-installed trailer-hitch option, which is supposedly pre-wired)?

Once I know where that is, is it just a matter of buying the green adapter and 4 pins to crimp onto my Prodigy controller for installation?

Thanks in advance,
AJ

 

It was a nightmare to get my brake controller installed. Mercedes was talking about $ 2000 to get it done. And this on a 450 GL with factory installed hitch with 7 pole plug. Then I went to U-Haul and got it done for $ 180.00. Unfortunately the LED lights on the trailer did not work and U-Haul spent a couple hours but did not find a solution. They gave up. I spent several hours on the internet to find a solution and finally found it. It is a $ 26.00 LED lamp-out bypass adapter from Tow-Ready.com (part # 20142).
U-Haul screwed the controller bracket in the under dashboard panel with self tapping screws. 2 days later it fell down because that flimsy plastic under the dashboard is not strong enough to hold the weight of the P3. U-Haul did not want to take down that panel and I went back to the MB dealer who did it and used bolts and nuts to fix the controller bracket safely. They gave me a bill for $ 350.00 for this job. Now it finally worked and the GL is towing just fine.
I am running out of MB factory warranty soon so I am shopping for a certified 2015 model 350 GL. I was told the 350 bluetec will do the job as good with much better gas mileage (resp. Diesel). But I'm afraid having to go through the same brake controller experience and Mercedes really sucks in supporting 3rd party equipment. My trailer is a 2-axle 7,000 lbs Toy Hauler. It is illegal to pull it without brake controller and if you have an accident the insurance won't pay.
I hope somebody will sue Mercedes for this and make them include everything you need to pull 7500 lbs.
Now i found a website with info on the new Tekonsha Prodigy RF. No need for wiring in the car. All installed on the trailer and controlled with a remote in the car that only needs the 12 V outlet. I would like to know whether there are GL owners that use this Tekonsha RF. It is $ 315.00 from e-trailer.com. This would be the nicest solution and no more expense if you change your car.
Any info on this unit would be very much appreciated.
Thanks

 

An old post, I seem to be having this same issue with a Curt Spectrum I installed using the x58 connector, I have tried plugging the trailer into the vehicle, but not driving w/ the trailer connected. (I have an '10 ML350 bt) Was your Test under load driving, or just connecting your trailer?

 

Hi @clorym ! I see you are still investigating.
I had forgotten my post, above, in 2011, and the Chat I had with a paid online tech. Also the same 3.9v problem you see.

Thanks for reminding me (when the Forum messaged a reply to this thread) because you had me scratching my head over your situation.
After I got that Chat confirmation, I just plugged in and everything worked just fine.

Post #40 above was apparently a miscommunication with the Dealer - the $2000+ tag is if you don't have the factory hitch. Then, U-Haul installed the standard generic wiring harness, which doesn't work with most Euro tow packages. The $350 is probably right for undoing the U-Haul setup and getting set up right.
Don't go to U-Haul or buy the generic E-Trailer (they are great) harness.

Look at the Chat I reported in Post #37 above. That's what gave me confidence to just start towing.
I know this whole thing is daunting - CANBus things often are.

I still don't know how your Curt controller will respond. Do you have a place very close by where you can just drive a block at low speed and try it out? At least that would provide data for your call to Curt's tech support.

 

I noticed you were the one after I had posted in the other thread!! I will just have to give it a try and see what happens I guess....I just figured plugging the trailer in should be enough for the system to recognize the connection and modify the voltages accordingly., I guess it must recognize something, because the only time the voltages on the Brake circuit goes to 12v when the pedal is pressed is when the trailer is connected..... Maybe it needs more before it will drop the voltage to 0v. I'll test it tonight and see what happens!!

 

The car could be looking for a completed ground pathway via the trailer coupler to ball connection. Can't say for sure - just offering an idea!

 

I just received a call back from Curt, they are thinking the unit may be faulty, They have no explanation for the Single red light when the trailer is connected & the Dual Blue lights when it is not...

 

It was likely mentioned above, but what is the vehicle setting currently set to... incandescent or LED? And what type of lights are on the trailer? That makes a difference - at least when using a direct, "normal" hookup... I'm not sure about when using a controller?

 

Looking at my Tail lights I have both LED's & Incandescent bulbs, The trailer has incandescent. As far as what the Dealer set the SAM to yesterday, I'm waiting for a call back from them.

 

Sorry, I wasn't clear with how I worded things... by "vehicle setting", I meant what is the setting for what it's "seeing" on the trailer side... ie, the SAM. Sounds like you're on top of that.

 

That's a good thought. You're right - the first step in troubleshooting 12V electrics ought to be verifying a good ground.
However, the 7 pin connector has a ground, so the ball mount connection SHOULD be redundant.
A ground can be verified by seeing if the trailer lights come on when the ML lights are on.

 

All the lights etc work properly on the trailer and are nice and bright, So I dont think there is a grounding issue, I will test with the trailer Hitch connected and see if there is a difference, although I dont really expect one...... I did drop by the dealer today & had them test with their trailer plug testing device, same result, voltage never dropped to 0v on the brake circuit. they didnt double check the rear SAM programming, but were confident it was correct, tomorrow they are going to test a known working SAM and see if there is a difference. I guess if all else fail's, I could potentially tap into the brake light wire and run it to the controller if the sam isnt an issue,