ABS sensor fault

[renrutp76]

Following a lot of recent work, I have a very frustrating fault..... My 2005 E500 has not been driven for a couple of years, and after charging the battery and taking for a short test drive there were more problems than I could have imagined which are covered in another thread. A couple remain, but I will post in the relevant sections. I currently have error 4636 (current and stored) right rear speed sensor, which activates the ABS ESP faults. I replaced the sensor, and checked the live values while spinning the wheel, and the value changes. I have reset the fault numerous times, but it reappears each time i drive the car. I am currently unable to drive at the moment to test further as my gearbox conductor plate is away for repair. I have also just replaced the discs and pad, not sure if that is relevant (it did mention worn discs in one of the fault causes. when I was looking through the live values the steering angle sensor had a value of 18, with an acceptable range of -2.5 to 2.5 although the next value in the list said steering angle sensor "OK".

has anyone else experienced this issue?

 

[ajlsl600]

You say the car was parked for a good while. Did you check for rodent damage and did you clear the reluctor ring of any accumulated debris and or corrosion

 

[renrutp76]

You say the car was parked for a good while. Did you check for rodent damage and did you clear the reluctor ring of any accumulated debris and or corrosion

if the reluctor ring was an issue, would live values in star show readings for wheel speeds?

 

[Blobcat]

Some replacement sensors give incorrect readings - was it a genuine Mercedes part?

 

[renrutp76]

Some replacement sensors give incorrect readings - was it a genuine Mercedes part?

Thanks for the info, no it was from euro car parts. I haven't been able to check the live values while the car is moving but will probably get a sensor from MB anyway. I did think the steering angle sensor value was very odd though, well outside the recommended range, but no fault.....

 

[ajlsl600]

if the reluctor ring was an issue, would live values in star show readings for wheel speeds?

Prob not, but if intermittent, maybe? I have a combination. Of aftermarket and benz sensors, we see which fails 1st?

 

[renrutp76]

Prob not, but if intermittent, maybe? I have a combination. Of aftermarket and benz sensors, we see which fails 1st?

Replaced sensor again, but fault remained. Also removed rust through sensor hole across whole circumference of the wheel. Can the reluctor ring be replaced or do I need a whole hub?

 

[ajlsl600]

Don't know ur model, check on an online pts listing.

 

[renrutp76]

got a new reluctor ring from MB, also lots of new heavy duty tools and managed to undo suspension bolts although a 10mm allen bolt is now ruined. Removed the hub nut using a 32mm 12pt socket, a 1/2 drive ratchet and a 10ft scaffolding pole. then after a bit of youtube, I fixed an old brake disc back to front, attached my biggest set of stilsons and beat it wit ha 4lb lump hammer. only succeeded in breaking the stilsons... Any helpful suggestions?

 

[renrutp76]

got a new reluctor ring from MB, also lots of new heavy duty tools and managed to undo suspension bolts although a 10mm allen bolt is now ruined. Removed the hub nut using a 32mm 12pt socket, a 1/2 drive ratchet and a 10ft scaffolding pole. then after a bit of youtube, I fixed an old brake disc back to front, attached my biggest set of stilsons and beat it wit ha 4lb lump hammer. only succeeded in breaking the stilsons... Any helpful suggestions?

Update.... abs ring replaced, swapped ABS sensor twice, still got an ABS fault. I have taken for a test drive viewing live values and every so often, the right rear value dips slightly for 1 read then recovers.... I have taken apart 3 times now and cleaned etc. Swapped the abs sensors over and I still have an issue..... please if anyone has any suggestions I would be incredibly grateful. I have spent almost 2 weeks trying to get this car back to normal after 3 years standing, and gave spent a small fortune. This is the last major fault I have to fix and need to get it on the road as I have spent 6 weeks in a hire car due to my main car having a failed turbo.... (italian reliability!!!!)

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[supernoodle]

Not had issues with them myself, but just thinking about what I would do next:

Check the pins in the plugs at both ends are clean, not splayed or pushed back.

Check the wiring for signs of damage.

I recall someone here made a temporary jumper harness so they could wire the left sensor into right wiring harness and vice versa. If the fault reports the same side it suggests wiring or module. Module very unlikely but you could always prove by swapping pins over at the module end.
If however with the jumper harness test the fault moves, it suggests it's the in sensor/ring combination somewhere, eg play/runout?

 

[renrutp76]

Not had issues with them myself, but just thinking about what I would do next:

Check the pins in the plugs at both ends are clean, not splayed or pushed back.

Check the wiring for signs of damage.

I recall someone here made a temporary jumper harness so they could wire the left sensor into right wiring harness and vice versa. If the fault reports the same side it suggests wiring or module. Module very unlikely but you could always prove by swapping pins over at the module end.
If however with the jumper harness test the fault moves, it suggests it's the in sensor/ring combination somewhere, eg play/runout?

Are the sensors connected directly to the ABS module in the engine bay? I am an automation engineer and work with programmable controllers and sensors daily. Just used to a bit more accesibilty than you get with a car! All pins have been checked and seem OK. Are the sensors individually fused or not. They seem to be a 2 wire sensor, does anyone know what signal they generate? I would expect a pulse based upon the magnetic impulse ring. I cut the cables and connected the sensor to the opposite connector via a temporary loom under the car, but now both rear sensors read 0 when the car moves even though the fronts read. For something safety critical, I would expect 4-20ma or similar (floating zero) so that if the cable becomes damaged the signal would be 0ma indicating a fault. At rest all read 0kph. Did read an old post on a USA forum where a faulty SBC module generated the same symptom. I currently have active faults in engine, gearbox, ABS, ESP, and power steering, all related to this fault.

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[supernoodle]

Rich started a nice thread about the sensors

Bench Testing ABS Wheel Speed Sensors

The W203 ABS Wheel Speed Sensors have an IC chip (Hall effect) inside. It's not possible to bench test them with a meter on Volts or Ohms. Attached is a simple circuit showing a way to test them. Please note this is to test them on the bench not connected in any way to the car. Avoid bringing...

forums.mercedesclub.org.uk

 

[renrutp76]

Rich started a nice thread about the sensors

Bench Testing ABS Wheel Speed Sensors

The W203 ABS Wheel Speed Sensors have an IC chip (Hall effect) inside. It's not possible to bench test them with a meter on Volts or Ohms. Attached is a simple circuit showing a way to test them. Please note this is to test them on the bench not connected in any way to the car. Avoid bringing...

forums.mercedesclub.org.uk

Thanks for the info... looks like it will be useful once I can get either of the rear sensor to read anything..... should I look at replacing the ABS module, or is there likely a fuse blown?

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[renrutp76]

Thanks for the info... looks like it will be useful once I can get either of the rear sensor to read anything..... should I look at replacing the ABS module, or is there likely a fuse blown?

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Update.

Cut ABS sensors and wired to opposite side, but only disconnected rear battery. When I tested only front sensors displayed a value so assumed I had blown the input channels to the SBC module. Mine is the original module so I decided to replace with a refurbished unit. After replacing and refilling, front drivers side wouldn't build pressure so assumed module was faulty. Now waiting on a repair!!!

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