Thread: R230 fog light's flashing with brake light's???

Hi all i'm a newbie to MB Guru so hope you guy's can help, i have a 2004 SL350 recently noticed when the foot brake is applied i get an intermittent fault of both rear fog lights flashing like strobe light's (extreamly bright) in no regular pattern i have also noticed the rear side light's (LED one's) have a very slight flicker.... with both fault's the flicker is simultaneous in both lamp unit's, also strange is that the n/s/r fog light flashes when it's playing up, but when the fog is swithed on only the o/s illuminates as it normally would!!! Hope someone can help Many Thanks Simon.....

This sounds like either an earth fault (most of the lamp looms connect to the same earth), a Rear SAM fault, or a rear sam power supply fault.

The easiest way to get this checked/sorted is to get the car plugged into Star Diagnosis ..

Richard

Sounds like a CAN-C fault.

Thanks for the quick replies, i did have it on Star last week but it was unable to communicate with some of the onboard diagnostic's having had a problem with the Can plug's under the passenger/drivers floor (brown wire's multiplugs) before i checked these and the driver's side was all green due to a previous blocked water drain problem!!!. i was advised to hardwire these plug's as that could be causing the communication problem's and it may even cure the fault, only got time yesterday to do it but the fault still persist's...... with regard to Can c i thought that was engine??? I take it the rear SAM control's the light's are they prone to failure?? thanks simon..

I think that you have water damage.

Ive been seeing more and more SL which have had water get into the passenger side wiring duct. This leads to

a) corrosion of the wakeup/diagnostic connector for the stereo (in duct behind passenger seat) - causing stereo issues and diagnostic issues

b) corrosion of the CANbus distributor causing all kinds of trouble.

For (a) I tend to cut the diagnostic distributor off and solder all the blue/black (wakeup) wires together, and all the red/something wires together (diagnostic on MY2004 and before) together, heatshrink and cover.
(This normally requires removal of passenger seat)

For (b) I disconnect all the plugs, clean them if possible or replace the pins and put a new CANbus distributor in.

And clean up any other electrical plugs in the area in a similar vain (there are a few). Of course I have a big box of replacement connector shells and elements.

Personally, i'd be removing the passenger seat, lifting the carpet to expose the whole of that wiring duct and inspecting for any water damage to any electrical connector.


Richard

Thanks Richard i have not looked behind the passenger seat, any issue's with removing the seat??, should i check both sides or is it only on the CD player side?? is it best to remove consumer batt terminal didn't want to cause an SRS fault or make more trouble for myself!! many thanks for the reply Simon..

When you remove passenger seat you will get a SRS light if ignition turned on (and may in anycase) because theres airbag related stuff in the seats.

There are 5 bolts for the passenger seat. E14 I think. (inverse TORX)

There is stuff in the driver's side aswell (including another CANbus distributor), but I think that is all at the front so you can get to that easily enough (have to remove accelerator pedal, which is 1 nut under the plastic round cover.

Theres one more CANbus distributor but thats next to the fusebox in the box behind driver - but its high up and thus not likely to have ever got damp. If it has got wet up then there are some much bigger issues.

If you near Lightwater in Surrey talk to the guys at Welcome to www.comand.co.uk who have the diagnostic kit and happy deconstructing SLs.

Cheers

Richard

Thanks Richard i'm hoping to have the passenger seat out tomorrow weather permitting, i have already removed the accelerator pedal and hard wired the o/s/f and n/s/f canbus plugs so hoping to find a n/s/r plug with the "green death" Many Thanks for your advice Simon..

Somewhere on the CANbus is a single terminating resistor. I can not remember where it is on an 04 SL. It could be in 1 particular control unit, or it could be on a special CANbus distributor - so watch for that

If you look at the wiring in each distributor there is one (or two) sets that are a different colour to the rest - these are the wires that go to the other distributor.

The bottom of the stowage box behind the driver unclips to reveal fusebox, the CANbus distributor is just about visible through there - door side of the fusebox (if you see what I mean)

Did you ever get a Star Diagnosis machine connected - was it able to see any control unit ?

Richard