could be as simple (and expensive) as a wheel speed sensor

you need to pull codes. and i dont mean obd codes. star codes.

 

Per mercedes tech data, anytime you have a abs light "and" ets or asr ect ect ect it is always going to be a abs fault. Abs will disable other systems such as bas, ets, asr if it detects a fault. Be looking at wheel sensors.

 

ABS wont necessarily influence steering unless it's one of the front speed sensors. Read the codes.
My bet is wheel sensor.

 

When my ABS light appeared, the steering became heavy and the cruise control no longer worked. Both of these latter functions have inputs from the ABS. The culprit was the brake light switch. I'm not sure that having the brake lights working necessarily means the switch is OK. It has 2 pairs of contacts (one pair make, one pair break), both of which must be OK for the ABS to work, but only one pair of these contacts is used by the exterior lights cct controlling the brake lights.

When you start the car and with it still stationary, does the ABS light come on immediately or do you have to touch the brake pedal or drive the car for it to come on? If it only comes on when you touch the brake pedal then it's very likely to be the brake light switch.

Mike

 

My 2c would be a Steering Angle Sensor, but that would show up in a diagnostics or when you read the codes

 

You got number 4 wrong. True, a malfunction in ABS does disable other features such as ABS. But not necessarily other things such as Cruise Control. When my rear wheel sensor was bad, ABS light was on and so was ASR. But I had cruise control because the rear sensors are not used for cruise control. My speed sensitive steering also worked fine. Once I replaced the rear axle sensor both ABS and ASE went away. This is why I suspect it is one of his front speed sensors because he doesn't have speed sensitive steering anymore.

 

On further reading, I think we're probably all right and all wrong - it depends on the year of the car and the mix of installed equipment. I know that my loss of ABS (brake light switch) resulted in loss of cruise control and speed sensitive power steering - and I can see why from the relevant ccts; others have experienced the same effects. Fixing the brake switch fixed all problems for me.

Yourself and gyrate have experienced a different mix of symptoms on later cars with a higher level of traction control compared to me - although the link I referenced earlier was for 1996 S600 and the owner did lose cruise control along with ABS and ASR as a result of the switch failure.

I guess the real point that I'm making in all this is that when the ABS goes down it may - or may not - be caused by the brake light switch; the switches do commonly fail so you're likely to need one some time; they only cost around $20, it's a 30 minute DIY job and you may get lucky.

I'm done.

Mike

 

Hi guys,
I decided to try the brake switch replacement. Got a brand new one from Mercedes (£13.75 GBP) and it took about 25 minutes to fit, the hardest bit was getting the 5 screws out to remove the lower facia. I used the mighty power of shouting and profanity and hey presto, away it came.
Bad news is I still have the problem. I brought it to my local garage and had any remaing codes cleared but the lights are still burning brightly on my dash :crybaby2:
Just to recap, ETS (I dont have ASR) and ABS lights still on. Power steering heavy but not gone. N.B. when I first got the codes checked it declared that 3 of my abs sensors were faulty. The garage cleared the codes and switched the ignition back on and the codes came back up immediately without even starting the car. Today after fitting the brake switch they have gone altogether but the problem persists...
Any and all help is greatly appreciated folks :bowdown:

 

PPS it has disabled cruise aswell

 

I'm really sorry to hear that a new brake light switch didn't fix your problem - and I'm just waiting for gyrate's and Sinned420's 'I told you so's'!

But the interaction between fitting a new switch and the cancellation of the DTCs does seem weird. Have you tried testing the old switch to see if it appeared to be faulty? I guess you would have to measure the contact resistance between the pairs of contacts when each is closed - only out of curiosity, of course. What year and version is the car? I recall that one poster found that he had an s/c in the centre brake light, bulb holder which caused his ABS problems so you could check the brake light fittings - since it seems to be straw-clutching time.

I think that's it for me.

Good luck,

Mike

 

lol its all good

switch is a good thing to replace anyway, needed or not as it will eventually fail. the little metal spring inside snaps with use

 

I'll check the bulb holder as you suggest. Just for kicks how do I (or can it be done) check to see if a sensor is gone on the abs? BTW the parts guys at Mercedes told me that they have never sold a rear sensor for the w140 and a handful of front ones. Reason I ask is a new front sensor is £80+ and whatever about splashing out on £13 odd 80 quid is a bit more serious.
I have read on here about modules (?) going pop and needing to be replaced, would that be the one with the fuses on lurking under a plastic cover under the bonnet (hood), just under the windscreen left side?

many thanks lads

 

Its true the rear sensors are less likely to fail, probably due to it not getting as much abuse as the fronts (less movement). But that does not mean it can't fail. One of my rear axle sensors (which are mounted on the differential for my model. Others on wheel hub) failed. I got the code pointing to the right one being "open circuit". Unplugged it and cleaned it, but still got the open circuit error as soon as key is turned. Car didn't even need to start.
The damn sensor looked good, can't see or feel any problems. Replacement cost ~$150.
As far as I know, the only way you can test it is to somehow measure the resistance while someone spins the wheel I think. It doesn't matter anyways, you probably do need to replace it, even if you found out it is broken, it's not something you can repair easily...

It is weird how you don't get the codes anymore. What code do you get from the ABS/ETS modules then? Something must be triggering it.

 

only way to know (and again depends on what shows) is to run a xentry on it (or some other star system). once you have your starting point you go from there. it will either give you a nice neat error location/item or a bunch of codes with the real cause/s somewhere in there. but that is for when you are in the system

the "ive never seen x fail" aint worth the time it takes to say. just ignore them. everything can and does fail.

 

I was digging thru the garage and ran across a couple of front abs sensors from a 95 s420. Think you could use them? For FFFRRRREEEEEEEE? Just shipping at a huge $10.00, your in the uk maybe 20.00

 

Come to think of it, I have an extra S420 Rear Right speed sensor as well. Its the one that goes to the wheel hub. I bought it only to find out mine was the one that mounts on the differential. So if you need it, I'll give it to you for free. I'll look up the part number later, and you could confirm yours.

 

ABS Stiff Steering

My 1995 S320 had the ASR light come on in conjunction with the ABS light... turns out it was the passenger side ABS sensor. Naturally on my model, manufacture date they used some type combination harness so the $160USD sensor (part number 140-540-35-17) did not work... I needed the $438 part (MB part number 140-540-17-09). Bit the bullet and installed a new sensor an no more ASR/ABS, stiff steering or delayed acceleration.

Eddie
1995 S320

 

hello guys I have a 1994 S420 that seems to have same problem has some of you diference is that mine turn the abs light on when i press the brake and it make sterring hard have to turn car of also brake seems to get harder mine does not have esp
1. Turn the car on, no light on, stering ok
2. Press brake lights comes on and stering becomes harder

any sugestions on this problem
1. Brake light switch
2. Faulty wheel sensor

 

Certainly sound like the brake light switch to me. When mine failed it produced those symptoms except that I don't recall any change in how hard I needed to press the brake pedal. It did also stop the cruise control from working.

Mike

 

incredible my problem was the 3rd brake light just dicconected the cable that fix the blown fuse and know sterring great, brakes excellent, no abs light

 

Glad you found it, and thanks for replying back.Your struggles will save a lot of time and money for others now that we know what to look at.All these fixes add up to a valuable resource on this board. Thanks again!
Mike