Brake lights and gear select.

steveskeggy

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S55 AMG
Hi.
I have a problem with my 2003 S55 AMG.
It has occured since getting the car running after 2 years rebuilding the engine top end.
The brake lights are illuminated constantly when I turn the key to position 2 (Dash lights on), or with the keyless.
It will also not come out of park, unless I tap the top of the selector with a rubber hammer.
I have replaced the brake light switch, to no avail, I tested the old switch with a multimeter and a wiring diagram of the switch from the web, the switch worked fine.
I have tried the new switch unmounted from the pedal bracket, the result is the same, In fact, if I disconnect the switch, it is the same.
It seems a bit strange that the lights are illuminated, which would point to the pedal being pressed, yet the selector wont come out of park which would happen if the pedal was not pressed.
I have the usual BAS ABS warnings come up, but I cant really drive the car as yet, because there are no brakes pads in it, because the discs need skimming.
In another post of mine, about a different subject, the rear SAM was mentioned if it wasnt the switch, this is my next move, even though its not throwing codes.
I have ordered a rear SAM just in case, if it is not the SAM then its always handy to have a spare.
Anybody think of anything else that it could be? Stop-Lamp-Switch.jpg
 
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steveskeggy

steveskeggy

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Joined
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Messages
165
Car
S55 AMG
OK, so tried a replacement rear SAM, still the same problems.
Now I am beginning to wonder about the ABS BAS ECU.
The reason being that the warnings don't go out with lock to locking the steering wheel, which it has done before.
The suspension button lights are remaining on as well, it has a cancel box from strutmasters, which also worked before.
I had to have the engine ECU repaired, because moisture had got in, and some of the pins were broken, so if one ECU can go faulty because of no use, then so can another.
 

AMGeed

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Turning the steering from lock to lock should put out the ESP warning message. I don't know whether that removes the BAS and ABS messages as well?

I would look at the gear selector as being one of your problems if it won't come out of gear and you've changed the brake light switch.
 
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steveskeggy

steveskeggy

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S55 AMG
OK so after many days of being unable to work on the car because of the weather, I have managed to sneak in an hour today between showers.
I read that if the BAS etc control unit was faulty, it would be hot after 15 minutes running, this was not the case, it was not cold, but it wasnt warm.
Still not entirely sure that this is not at fault.
I connected the Maxidas again, and found two readings that are quite interesting.
"The stop lamp switch signal sent from the traction system via the can bus is implausable"
This is what is making me wonder if the BAS etc module is faulty, it would explain the warnings on the dash, and possibly the brake lights.
"Drive authorization routine in control module ESM active - No 2205452932"
This is the part number for the transmission control unit, which would explain why the selector wont come out of park, but the brake lights and the dash warnings?
If this turns out to be faulty, is it part of the demon three, with the EIS and Key, that have to be changed together?

I dont know how I got to it, but I searched around the internet, and came up with the BAS Diaphragm position sensor, cant remember what it was concerned with, except the BAS warning, obviously, but could a fault in this cause the brake lights to be stuck on?

Regards

Steve.
 
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steveskeggy

steveskeggy

Active Member
Joined
Jul 4, 2011
Messages
165
Car
S55 AMG
So this morning I decided to check the operation of the new brake light switch.
It worked fine.
However, I also decided to check to see if there were any supply voltage coming down any of the leads other than the two feeds from the fuse.
There were no 12v feeds on any of the pins, and there should have been at least those two.
I went back to the fuse, and it still looked fine.
However, using my multimeter, it turns out that the fuse was not working!
I popped a new fuse in, now everything works as it should.
The lever moves when I press the brake pedal, the brake lights work properly, and all of the warnings on the dash disappeared, except for the pre-safe, which went when I lock to locked the steering!
All I need to do now is tidy up the brake discs, refit the pads, and I think I can take it for MOT.
Happy days!
 

AMGeed

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Glad you managed to find the problem.
Imagine if a dealer had got his hands on it before you found the fault:eek:
 

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