Brake wear sensor warning - not always brake pad related
08-22-2018, 11:17 PM
#1
MBWorld Fanatic!
Thread Starter
Brake wear sensor warning - not always brake pad related
to all those that might be experiencing a brake wear warning notice on the dash ; it is not always pad related or even sensor related.
I had the warning come on at full lock of the steering wheel, and had changed the sensors preemptively thinking this might solve it.
It turned out to be a faulty harness of the brake wear sensors. I have attached the service receipt and diagnosis with part numbers for anyone who may find it useful.
Cheers
Kombifan
08-23-2018, 10:33 AM
#3
actually, very common. right front and rear sensor harnesses are attached and routed for some reason in a way where they are subjected to a particular twists resulting in failure. 07 and 08s are very prone to that...
08-23-2018, 12:27 PM
#4
MBWorld Fanatic!
The early ones, yes, but as they all got the updated holders and wiring, it happens far less often.
08-23-2018, 03:07 PM
#5
MBWorld Fanatic!
Thread Starter
08-23-2018, 03:46 PM
#6
Senior Member
Apparently these were a problem for a while on the GL's
I ordered new pads (mine were on for a few years) but when I pulled the wheel and went to replace front pads, they were still about 50% remaining.
Then looked at the back pads and they were fine too. So I ordered the front harness knowing these go bad. Not the problem either.
Finally hooked up my DAS/STAR laptop and drove until the error came on. It reported the front sensor as OK and the back as NOT OK
Pulled the back wheel and inspected the wiring closely. The rear harness was fine but the connector it plugs into (on the body harness) had a broken wire right at the connector.
Ordered about $25 worth of parts (two crimp connectors, weather seal, connector) which looked like about $1 worth of parts
Stripped both wires, crimped new pins, inserted into new housing/connector. Haven't had a problem since.
Check closely the front and rear harnesses, but also the connectors they plug into for the body wiring harness.
Any intermittent short will cause this. In my case the wire was intermittently touching.. some days it would happen every hour, other times it would happen 10x in a 10 minute trip. Was driving me nuts!
I ordered new pads (mine were on for a few years) but when I pulled the wheel and went to replace front pads, they were still about 50% remaining.
Then looked at the back pads and they were fine too. So I ordered the front harness knowing these go bad. Not the problem either.
Finally hooked up my DAS/STAR laptop and drove until the error came on. It reported the front sensor as OK and the back as NOT OK
Pulled the back wheel and inspected the wiring closely. The rear harness was fine but the connector it plugs into (on the body harness) had a broken wire right at the connector.
Ordered about $25 worth of parts (two crimp connectors, weather seal, connector) which looked like about $1 worth of parts
Stripped both wires, crimped new pins, inserted into new housing/connector. Haven't had a problem since.
Check closely the front and rear harnesses, but also the connectors they plug into for the body wiring harness.
Any intermittent short will cause this. In my case the wire was intermittently touching.. some days it would happen every hour, other times it would happen 10x in a 10 minute trip. Was driving me nuts!
