Brake wear warning message

[Sharp]

Hi, new to this forum as a member although have used it for obtaining some very helpful i fo in the past.
I have a 2006 CLK 320CDI. My issue is that the brake wear warning message wont go away. New pads AND new sensors fitted, expected the message to disappear as it had in the past after previous replacements, but on this occasion, neither front nor back pads were worn and sensors were not in contact with the disc - but since I had new pads and sensors I fitted them anyway! So, having perused this and other forums for info on more subtle reasons for this (eg damaged wiring to SAM, or bad SAM) but came up empty. So, decided I needed to post this in thehope that someone else has experienced and fixed this issue. I am a degree qualified electronics engineer so have no qualms about delving into the vehicle electrical system. But I cannot find any info on where the sensors connect into the rest of the car electrical system. Anyone have a wiring diagram that may help? Anyway, ny main concern is that now warning lights (and I assume messages) are automatic MoT failures - despite the fact that the brakes themselves are all A1. Anyway, any inputs gratefully received. Thx

 

[onefortheroad]

Try an OBD2 scanner to erase error codes.

 

[Sharp]

Try an OBD2 scanner to erase error codes.

Hi Onefor the road, thanks for your input. Have already tried this with no success.

Also, I have measured the resistance of the sensors. One measures about 0.1ohm, the other about 0.3ohm so almost short circuit which is correct for the 2 wire type sensors as far as I can determine.

If anyone is able to confirm where the sensor wire cables enter the SAM (which SAM?) or fuse box that would be a massive help I could trace back but right now I have no idea where the go once the disappear under the car body.

Thanks in advance for any inputs.

 

[onefortheroad]

Hi Onefor the road, thanks for your input. Have already tried this with no success.

Also, I have measured the resistance of the sensors. One measures about 0.1ohm, the other about 0.3ohm so almost short circuit which is correct for the 2 wire type sensors as far as I can determine.

If anyone is able to confirm where the sensor wire cables enter the SAM (which SAM?) or fuse box that would be a massive help I could trace back but right now I have no idea where the go once the disappear under the car body.

Thanks in advance for any inputs.

Try disconnecting the sensor from the loom ,then inside the loom you'll see 2 pegs , if you bridge these with wire or tin foil ,the warning should reset . This will rule out the wiring and point to the sensor being faulty.

 

[Sharp]

Try disconnecting the sensor from the loom ,then inside the loom you'll see 2 pegs , if you bridge these with wire or tin foil ,the warning should reset . This will rule out the wiring and point to the sensor being faulty.

Many thanks - again, tried this also with no joy, problem seems to be beyond the connector into which the sensor plugs at the caliper. At this point I am not sure whether it is front or back which is the issue so am trying all potential solutions on both front and back but so far no success.

 

[Sharp]

Hi Everyone. I have identified the source of the problem and want to share -although hopefully no one else ever suffers from the same root cause. To recap, the brake warning message would not go away despite new sensors. I had also measured sensor resistance and also simulated sensors at the caliper by shorting the pins of the connector together. Having done this I had proven the fault to be within the rest of the system. I was able to check continuity from the caliper connector to the bulkhead connector behind the shock absorber - again this was ok so proved the issue was beyond that point. So moved my focus into the engine bay, After removing the rain cover from the front SAM (off-side) I noticed a lot of leaves/acorns…….long story short, a rodent had obviously built a nest and at some point had chewed thru some wiring. I can see the damage with but it is an absolute pig to get to. Looks like the brake fluid reservoir will have to be removed in order to actually get to the damaged wiring and repair it. But being so close to the SAM I guess I am lucky that the pesky critter chose to chew thru something relatively innocuos - probably could have been much worse!

Anyway, can anyone help me with the location as to where this cable (carries the brake sensor and ABS sensor signals) connects into - I am assuming the front SAM, have downloaded the fuse/relay assignments but not the cable/socket/plug assignments that connect into the SAM.

Special thanks to onefortheroad who responded to my initial post.

Thanks in advance for any info on the SAM connection point for this cable.

 

[brandwooddixon]

A shame that MB no longer sell their pine martin deterrent engine bay undertrays.