ABS warning

[cjb44]

I have a C200 on a 63 plate. The ABS warning has come up on the dashboard along with the message that the run-flat is inoperative. I do not have the skill or knowledge to deal with this as modern electrics are not my thing, I am assuming that I probably have a sensor problem or maybe something more sinister. The annoying thing is that it is intermittent, sometimes it will stay off for the whole journey, sometimes it will be there almost from startup. Before I take the car to my local specialist are there any checks I can make, am I missing something blindingly obvious?

Thanks.

[Athlon]

Purchase some electrical contact cleaner in an aerosol.
Locate the ABS unit under the bonnet (all the brake pipes end up here, on a W204 it's on the near side towards the front)
Carefully separate the wiring harness from the unit, the loom plug is a teeny bit fiddly but you will work it out easy enough.
Spray the contact cleaner in the pins of the ABS unit and into the terminals on the plug.
Attach and detach the loom several times to work the dirt off the connections
fit the plug back and make sure it is firmly locked home
Cross your fingers that it worked and try it!

This has worked for me on several Mercedes, it is not always the sensor, usually if it is the fault is permanent, even if it does not resolve the problem it rules it out for a few quid on contact cleaner and it is a good job to have done.

After that you need a reader to see the data from the sensors.
Good luck

[autocrazy]

What a co-incidence my car a 62 C200 has the same symptoms of ABS-ESP light coming on intermittently (temperamentally) as OP

I will take the advice of ABS modulator and spray the connector with WD-40

Having applied logic I came to the same conclusion that an intermittent fault cannot be a duff sensor, has got to be a connector issue

Will report back on how it goes in a few days

[Penelope Stopit]

Sensors can fail at a certain temperature

[cjb44]

Thanks, Athlon.
Have been out to the car and located as you describe, have taken off the outer dust cover, and can see the block to which you refer, beside this block at the bottom is another plastic clip of the type that you force outwards to release. So far it has resisted my attempts, do I need to get more aggressive with it? Also, this cover is not solid and can be moved about slightly but the wires do not move at the same time, I assume I need to get this second cover off as well. Sorry for my ignorance but I have never played much with modern machinery, look forward to your further advice.
Many thanks.

[Athlon]

Best to Google how to remove the clip, from memory you slide the outer bit back and the plug will start to rise up, it will make sense when you try.
Do not use wd40...get some contact cleaner, wd etc adds residue where we are trying to remove it.

Please don't bugger it up, if you are still struggling with the connector I will try and get some pics tomorrow to help.

[autocrazy]

Hi. Just sprayed electeic contact cleaner (available at Halfords). It needed a bit of force to open the connector but a YouTube video helped

Early days, so far no code, but have not driven it extensively to be sure. If it goes away in the next fortnight-month will update over here

Thanks for the amazing pointer and I hope it works for me

[cjb44]

Well, guys, thanks for all the ideas and advice. With a bit of brute force and ignorance, I managed to free the plug and gave it suitable clean and a dose of switch cleaner. Took the car into town today and the warning did not appear, that is not until the return journey when nearly home and it duly came on.
I am having it diagnosed tomorrow at my friendly independent, he tells me he thinks that on my model year the axle nut can come into play as the sensor point but not sure until he checks. Suspect, I will be looking at a sensor problem and a lighter wallet as a result.
I Will report back on the result.

[stevemcs]

Most likely the ABS sensor, fit genuine, they are approx £50 plus vat and then 30/45 minutes to fit. It sometimes brings the ESP light on too.

[cjb44]

Had the car diagnosed yesterday, fault showed as nearside front not sensing (or some such wording), booked in to be fixed at £160.00 all in; seemed fair to me.

[autocrazy]

My lights back too - guess it is the sensor next

[Stegel]

Defective brake light switches on many MBs will give ABS, ESP and tyre pressure monitoring warnings as well - £15 and 5 minutes to swap. I’m on 2 out of 3 times the switch curing the issue - the third time it was a disintegrating reluctor ring upsetting the ABS sensor.

[autocrazy]

cjb44 said:

Had the car diagnosed yesterday, fault showed as nearside front not sensing (or some such wording), booked in to be fixed at £160.00 all in; seemed fair to me.

Hi OP - did you have this problem fixed - did changing the ABS sensor solve it?

[cjb44]

autocrazy said:

Hi OP - did you have this problem fixed - did changing the ABS sensor solve it?

Yes, it did and my wallet is now lighter!

[autocrazy]

Thanks. It's strange as the temperatures have plummeted the error comes less offer if at all. My cars MOT is coming up next month so will be an opportune moment to sort it if the problem continues to persist

[autocrazy]

Hi

Just a quick update. I had both front sensors changed with Bosch sensors (could have got away with one RH side but decided to put geo new ones)

It fixed the problem.

Heck I have already sold my car by now, on to something less glamorous but abuse friendly with two young kids

[cjb44]

autocrazy said:

Hi

Just a quick update. I had both front sensors changed with Bosch sensors (could have got away with one RH side but decided to put geo new ones)

It fixed the problem.

Heck I have already sold my car by now, on to something less glamorous but abuse friendly with two young kids

I am afraid we have all been there when a family comes along, never mind your time will come along again when they have flown the nest; I am now looking for my favourite V8 and in my 70's I feel that I now deserve it!