[RustyTheDog]

Hi all - any bright ideas on narrowing down the location of my issue?
Seems there's a wiring issue somewhere between the wheel sensor and engine bay.
Had right rear ABS sensor code 3 months ago and swapped out the sensor (new genuine from dealer) and cleared everything and all was fine for a while - but now seems the sensor might not have been the problem.

ABS/ESP lights came on and limp mode activated.

iCarSoft codes show:
C1103-004 (RR speed sensor loose contact)
P1860 (traction system RR wheel RPM error)
C1103-002 (RR speed sensor open circuit in wiring)
I have live sensor feeds of speed from all 3 other wheels, RR wheel is permanently flatline.

Qs:
Best way to check the sensor to establish the sensor to plug section is OK.
Where next to look / tests to do? Anywhere the harness commonly fails, visibly or otherwise.

Cheers people!
RTD

 

[Avel Du]

@Dave2302

 

[BaD_81]

Hmmmm what does a sensor do? Sensing, duh!
What is the sensor sensing? Uuuuuh those ups and downs of the "tone" rings each wheel has!
How does these get transmitted to the car ECU? Wires!
Wires but ...?!? Yeah wiring diagrams time!

Translated:
ABS sensor could be good but the reluctor ring being rusted-out of shape...= no signal and/or pieces of rust flakes got into the wrong part of the sensor.
Wires connecting the TCU (2001 is not like 1998, can't help) could be - recently someone mentioned the boot was full of water - rotten/damaged/missing = no signal.
TCU itself has few connectors - wires, locks...they need checking too, especially if the (Sci-Fi, right) connector plug of the gearbox is being FUBAR and let tranny oil seeped up into the TCU.

So, the scanner accessed TCU and saw 3 out of 4, but the questions are not answered...well it is time to get dirty and lay under to see what is not OK!

Multi-meter can confirm if the wires are OK or damaged.
If wires come up as good, reluctor rings-visual inspection.
If they are good too, RMA of the sensor, as it lasted less than a year!
Just for the record, what happened wit the "original" (I guess) sensor, you have it or?

 

[Avel Du]

We have seen the ring cause similar issues.

However, should you need them:

Wiring diagrams for SLK320/230, Fuse locations for SLK320

No diy here, but these should help electrical diyers. Thanks to @Dave2302 for supplying this data.

www.slkworld.com

 

[RustyTheDog]

My understanding is that due to the wheel sensor type I cannot simply unplug the sensor and probe the pins while spinning the wheel to check for output.

The reluctor ring looked surprisingly good, albeit 3 months ago. I’ll take another look tomorrow. Got the old sensor somewhere (a merc one, don’t know if it was the original).


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[M4rCu5]

Qs:
Best way to check the sensor to establish the sensor to plug section is OK.

Where next to look / tests to do? Anywhere the harness commonly fails, visibly or otherwise.

You can open up the connector plug for inspection of integrity, as was the case with one of mine..

 

[RustyTheDog]

So, car this morning all working normally again, no errors and reading wheel speed fine.

Pulled the rubber bung to check wiring to find water in the connector on the main harness side. Cleaned it all up and refitted. Working well.

So looks like I need to remove the trim panels to chase water ingress into the boot, though all seemed dry.


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[BaD_81]

So, car this morning all working normally again, no errors and reading wheel speed fine.

Pulled the rubber bung to check wiring to find water in the connector on the main harness side. Cleaned it all up and refitted. Working well.

So looks like I need to remove the trim panels to chase water ingress into the boot, though all seemed dry.


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Wd40 can push some moisture out, but contact cleaner/TRW brake cleaner should wash off the grease/dirt ...etc. vaseline and or silicone grease were debated on power connections(battery terminals) but can not be certain if applicable in this case.
So a bit of more reading could be helpful!
Edit
Some suggestion under the comments:

BAS/ESP & ABS

Seals around lights, number plates for above. Drain plug beneath spare for below.

www.slkworld.com

 

[M4rCu5]

BAS/ESP & ABS

Seals around lights, number plates for above. Drain plug beneath spare for below.

www.slkworld.com

I was going to say that this all seems very familiar - and it is!

So, car this morning all working normally again, no errors and reading wheel speed fine.

Pulled the rubber bung to check wiring to find water in the connector on the main harness side. Cleaned it all up and refitted. Working well.

So looks like I need to remove the trim panels to chase water ingress into the boot, though all seemed dry.

That connector does seem to be the source of your problem.
Much like yourself, I bought a new sensor to cure what started off as an intermittent issue in the 200 and then discovered that that wasn't the issue - you wont be the first if this proves to be the case 🙃

It was only when I went to fit the new sensor that I opened the connector up and discovered the creeping rot inside the cable, the wire in my pic ^^above^^ only had a couple of strands still holding it together 🤷‍♂️

After affecting repairs, I kept that brand new sensor in my spares drawer for years until it found a new home in the 320 - I knew I'd need it one day

 

[RustyTheDog]

Yes, at least I’ve identified the issue. I think I must have more water in it as I can set it off with certain manoeuvres. Will have a further root about to look.

Then I can set to look at the pulley that’s started chirping!


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[RustyTheDog]

Looks like the rubber seal below the rear screen is the culprit, so pending some better weather to properly remove it and apply sealant, I’m testing the waterproof capabilities of gorilla tape.

I got the side trim off but couldn’t see the rubber grommet and wiring connector for the abs sensor - not sure if I could have got to it by removing the large metal panel (fuel tank shield?) from the boot side or if access is via the cabin behind the seats.

 

[RustyTheDog]

For completeness of the post - access via the rear speaker holes looks promising

 

[LeonardoDaBenz]

Marked as Resolved