W202 ABS light on

[W202Paul]

I've a W202 1995 C180 Classic manual, with just over 143100 miles. Today in stop start traffic the ABS light came on and stayed on. I've searched the threads on this subject and these faults/checks have been suggested:

ABS cable connections
Cracked/dirt reluctor rings
Wheel speed sensors
Brake light switch

Can anyone suggest a step by step diagnosis to find the problem?

My brake lights work normally so does that rule this out as a cause?

 

[W202Paul]

I did a bit of research last night and it seems a faulty brake pedal switch is a common cause of the ABS light illuminating. On starting the car this morning the light extinguished as normal, so I'll just keep an eye on it in the coming months.

 

[Grahamcol]

I did a bit of research last night and it seems a faulty brake pedal switch is a common cause of the ABS light illuminating. On starting the car this morning the light extinguished as normal, so I'll just keep an eye on it in the coming months.

I don't think the brake light switch will cause that on a pre-facelift 202, which yours will be. Best get it on star.

 

[W202Paul]

Thanks for he advice. My car came with the September 1995 revisions, the most notable being the passenger airbag (does that makes any difference)?
I'm a complete novice when it comes to code readers. Where is the diagnostic plug located and how many pins does it have? How do I know which code reader to buy?

 

[Grahamcol]

If I were you, I think I'd just take it to a good Mercedes Independent (not main dealer). They'll put it on star for around £40 and you should get a fairly instant diagnosis. However, if you want to diy, the "interrogation" point is under the bonnet just below the nearside base of the windscreen. You'll see a black "box" with a round plug. It's there. I don't know how many pins it has. But if you're not sure I'd definately take it to an Indy.

 

[W202Paul]

Thanks. I've also read the other similar thread on this issue. The ABS light has only come on briefly twice, both times after a long run when I've restarted the car. I'll keep an eye on it.

 

[andy27168]

Hi,
A Grahamcol has said it is very unlikely the brake light switch on your age of 202, you only have three ABS sensors, unlike the later cars with four.
You have one on each front wheel and as the reluctor rings on the front are part of the front hub they are not separate items and are very unlikely be cause of the problem.
In the set up you have the rear one which is in the diff is most likely be the cause of your problems, as they eventually corrode in place in the diff swell and seize solid in the diff.
It might be worth familiarising yourself with the rear sensor, possibly remove it (if its not already seized in there), give it a clean up bit of grease on it and refit it. The sensor comes into the car and plugs in, from memory its under the plastic panel on the boot floor behind the rear seats.

 

[W202Paul]

Thanks, I'll do that when the weather improves.

 

[W202Paul]

The workshop manual says I have to renew the rear sensor retaining bolt. Do I? If I do, are there any websites that show exploded views of assemblies with associated part numbers?