babason

Hello guys, Finally found out how to place a thread on this site....shows how much I know.Can any of you clued up techs, help me.

2000 slk 170 230kompressor. Fault codes says left rear wheel speed sensor not working. check actual values and spin wheel Nothing on scan tool. try right side am getting readings. I want to narrow it down exactly so I connect a meter up to the left side rpm sensor on ohms. open circuit, fine I try the right side, open circuit as well ????? can anyone explain why. I then connect the meter up but switch to ac volts and get nothing when i spin the wheels by hand or drive it with the wheels off the ground. I have checked the 2 wires from the wheel speed sensors, to the control unit for continuity and they are good. So i have ordered a left speed sensor but am not sure and dont know what, if anything am doing wrong with the meter. Any suggestions mightly appreciated.

I know the meter is fine

exit2Ek

i don't remember if the left and right wheel speed sensors are interchangeable. if so can you swap them from left to right and see if you
code jumps to the other side. also if you have access to a scope you can
hook it up and look at the readings while in motion. most likely you'll fix the problem with just replacing the part. let me know how it turns out. good luck.

MBTech21

the open circuit is normal....new type of sensor we went to around then..probably just the sensor, but exit2 is right..a scope is the only reliable way to check it for sure

babason

Hi guys sorry i havent replied sooner. busy.
thanks very much 4 your suggestions/replies

First of all the sensors R not interchangeable, they are actually marked left and right .

Secondly I suspected,that like MBtech21 said open circuit is normal but cant understand why. I thought the sensor acted like a magnet and the hub cut the lines of force from the magnet(sensor) hence signal sent to control unit over can, so if i plug in multi meter on a/c milivolts, surely i should see something ??

Thirdly I questioned the bloody service receptionist, and after threatning ......him he

finally admitted that the vehicle was on its third visit and from what i can understand, originally the vehicle came in for a water leak in the boot, (boot still smells damp) some seal or the other was replaced by another tech. Then the vehicle came in with the esp/bas light on. no idea of time span. Apperently DAS reported the right wheel speed sensor. at the time, and that was replaced. vehicle went out and light came back on again. which i think is when it turned up on my door step, with left wheel speed sensor. I already had my suspicions because during my initial checks the right sensor looked new.

Due to the dampness in the boot I have already checked both plug terminals for corrosion , nothing. they both look clean/dry.

I have fitted the left sensor that has come in and road tested vehicle twice no problems. I have had to advise the receptionist and leave the vehicle because of the issue of who is paying for the labour and parts, but I suspect the vehicle will be back once the customer takes the car away. and drives it extensively. ...... PHEW.

Hence the reason I want to be sure on how to test these wheel sensors, and any other ideas you genius may have.

I have a blue-point mt599a automotive scope and will try that. any ideas as to what settings i should use ?????


Thanks for reading my story...

MBTech21

I don't remember exactly the settings, I have mine programmed in..I'll look tomorrow and let you know.
BTW...it doesn't go over Can either..it is hard (or 'discrete') wired to the ESP

babason

Thank you Sir

as usual you are right cause, I checked those wires, from the speed sensors to the esp unit for continuity and they were fine.