[Durkatlon]

Have you tried to pull up all the trunk carpet and look at the Rear SAM directly to see if there's any components spliced into any wires that look out of place?


See middle of page 1 of this thread for what Rear SAM looks like after carpet is removed and metal panel is loosened and rotated:


https://www.slkworld.com/slk-r171-g...171-general-discussion/535069-powering-central-locking-via-rear-sam-module.html


See here for instructions on pulling up the carpet:


https://www.slkworld.com/slk-r171-general-discussion/38233-fuse-box-trunk.html

 

[efair]

@Sneaky Pete are you sure about your"half and half" theory? I'm not arguing with you, I'm just curious after reading some Google results. I went out to my car at lunch to see if I could confirm your theory... I had to use my phone to make a video and I got lots of funny looks! After doing so, I couldn't confirm or deny because the lens is impossible to see through.

 

[Durkatlon]

@Sneaky Pete are you sure about your"half and half" theory? I'm not arguing with you, I'm just curious after reading some Google results. I went out to my car at lunch to see if I could confirm your theory... I had to use my phone to make a video and I got lots of funny looks! After doing so, I couldn't confirm or deny because the lens is impossible to see through.

It's actually not half-and-half, but PWM for tails, vs "always on" +12V for brake lights.



Here's an o-scope showing the duty cycle of the PWM signal that constitutes the tail light signal. It has a duty cycle of just 7% on vs 93% off. I was surprised how short the tails blip on to produce the normal rear light illumination:

 

[efair]

So it's not separate LEDs? The tail and the brake use the same LEDs, just with a different signal applied?

I read somewhere that the lumen ratio is supposed to be 10 to 1 - the brakes should produce 10 times the lumens as the tail lights- so 7% is about right.

 

[Durkatlon]

So it's not separate LEDs? The tail and the brake use the same LEDs, just with a different signal applied?

I read somewhere that the lumen ratio is supposed to be 10 to 1 - the brakes should produce 10 times the lumens as the tail lights- so 7% is about right.

Yeah that sounds about right then. It is indeed the same bank of LEDs just driven differently. I actually just finished a control circuit that takes this 3-state signal and drives 2 completely separate banks of LEDs (one for rear, one for brake) at full brightness:. This was to replace a part of the popular after-market tail lights for the R171 that had broken for a forum member here.



Sorry about derailing the thread. Back to your regularly scheduled programming!

 

[Sneaky Pete]

@Sneaky Pete are you sure about your"half and half" theory? I'm not arguing with you, I'm just curious after reading some Google results. I went out to my car at lunch to see if I could confirm your theory... I had to use my phone to make a video and I got lots of funny looks! After doing so, I couldn't confirm or deny because the lens is impossible to see through.

No not sure. It sounded plausible to me but I see I far more knowledgeable member than me has just explained how it actually works. Like I often say, you learn something new here every day!

 

[efair]

Did you make these traces with the lights disconnected or connected?

 

[Durkatlon]

Did you make these traces with the lights disconnected or connected?

Are you talking about that o-scope picture? That was with light attached. I think the car would have a cow if you turned the lights on without any housings connected. Probably some of what the O.P. is experiencing.

 

[efair]

Burnsi, none of this is going to help you with your issue. I do wonder though, 1) how the SAM knows there is a short or an open in the LED circuit 2) if the SAM requires some type of reset to restore it to normal behavior, and 3) if the SAM keeps transmitting the PWM signal even after it detects the line is open.

I'm going to have a look at SDS tomorrow.

 

[Burnsi]

I was mesduring bolts on All lights.
All of them are working, only the gray/Black was not.
This is on both sides.

I deleted all error Codes and cut the battery for 10 min.

Same errors.
Maybe i have to pay some new lights for testing.

Gesendet von meinem Mi MIX 2S mit Tapatalk

 

[Durkatlon]

The SAM should not have to be reset to "see" the lights again after they were temporarily removed. I've done this many times and I've never had to do anything like that.

The rear/brake light will draw a maximum of 50mA. So at 12V this means you can splice a 220Ohm/1W resistor across across the #1 and #5 pins to make the car think that the light is there. You could do this on both sides simultaneously and at that point you should be able to remove the lights completely and still have the car think that they're there.

If it still ends up in "ersatz" mode, and there is *definitely* no modification to the wiring loom between the SAM and the tails, I would start to suspect the SAM itself being defective.

 

[efair]

@Burnsi what was the voltage on the gray/black when you press the brake pedal? 0V?

 

[efair]

Do German cars have the center stop lamp (CHMSL) too? I'm wondering if this might be in play.

 

[Baja-D]

We should not forget that his car is a German version and may be built to different Gm/EU regulations....maybe lights and/or wiring are not US standard? I would suggest going to the MB dealer in Germany and seeing what all the rear lights actually are for this specific car and if different from what is in the car. Another idea...could different front lights cause a weird issue also?

Baja-D

 

[Durkatlon]

We should not forget that his car is a German version and may be built to different Gm/EU regulations....maybe lights and/or wiring are not US standard? I would suggest going to the MB dealer in Germany and seeing what all the rear lights actually are for this specific car and if different from what is in the car. Another idea...could different front lights cause a weird issue also?

I've worked on the R171 tail lights a *lot* , including supplying many modifications to European owners. See here:


https://www.slkworld.com/general-mo...m/general-modifications-r171/29482-do-led-taillights-cause-bulb-out-errors.html


The difference between North American and ROW (Rest Of World) spec is only the lack of pin#4 (side-marker) on the Euro tails; the rest is identical.



The headlights are on a completely separate SAM so they do not interact. The symptom he is seeing is typical for a burnt-out rear light on either side of the car: it goes into "emergency" mode and uses other bulbs in the tails to take over from the normal rear light bank.


I think the experiment with the resistor is worth while. Those are less than 1 Euro each which is quite a bit less than buying a second set of tail lights to experiment with. I'd say if the resistor experiment does not give any new information, it's time for a dealership visit (and a new SAM? hope not, but ...)

 

[Burnsi]

Hi,

I got xentry now and i can test the lights.
Left are OK, every Light works.
When i Switch the right Light or Brake Light on the Software Shows for a Quarter second on an goes to off.
My Voltmeter is to slow but i can messure that i got voltage on the right wire.

Next i've tried a used rear Light and i got the same errors. So its nö Problem with the headlights.

 

[broker2009]

Burnsi,

I'm having same issue with fog lights but only on the right hand side. and the left side license plate lamp. I thought the fog was a connector issue as when I purchased the it was not working and I seem to recall getting it to work by wiggling it a bit. I ignored it b/c I rarely use the fog lights. Now I would like to get it working and it is irritating me. The license plate light went out, started working when I closed the hood then went out again.

I'll let you know if I work anything out.

 

[Durkatlon]

...I'm having same issue with fog lights but only on the right hand side. and the left side license plate lamp. ...

Your fog problem is actually not a problem: the rear fogs on the R171 only come on, one side at a time. Normally the left fog is on when you pull the light switch all the way out. The right fog only comes on when the car detects a problem with the left one. There is a way to program the fogs to both come on simultaneously but from the factory this is not how it works.



The license plate light is a separate issue.

 

[Burnsi]

Hi,

Today i messure the wire from Sam-r to the Light connector.
I cant find any issue, i think the Sam is broken.

The number is 1715450301.
Unfortunately i cant find this number, only others with "replaced with......" note.

Can i replace mine with a 1715451301 sam?

I think this is the newest for r171.

 

[Burnsi]

Here what i found for sam-r

https://photos.app.goo.gl/s7tPwt9zB1mYEX5F7