EPS ,BAS problem on w210

[lotus160sport]

Wondering if anyone can help just recently my bas and esp light has switched on on my 1999 e430 w210, so I took the car to my local indy who said it is sometimes down to the brake switch which he changed. The next morning it comes on again so I phoned him and he said it could be low voltage on the battery, so we ordered a new one and guess what? This morning the light has come back on, does anyone have any other ideas to what could be doing this as this is getting expensive, just to note the light comes on when I drive of in the morning and the brake peddle makes a single clunk then the light switches on although it has been making this clunk for quite a few months with no light. Hope this makes sense.
Cheers Greg

[pist nbroke]

Could be a number of things Greg-

Brake light switches are common on these, do a quick check to eliminate it/make sure he replaced it.

To check the brake light switch, place and hold your foot on the brake pedal, then put the key in ignition and start the car. Wait a few seconds and the light should not come on. Now release the brake pedal- if the light comes on instantly, in my experience its the switch.

Failing this it could be a number of sensors - steering angle, wheels speed. Or an ECU. A good MB specialist should have a "star machine" or equivalent code reader to identify this. Unless its a wiring fault, a bit more in depth.

[lotus160sport]

Cheers for the reply alex I will have a look at the brake switch again and then have a look down the other avenues.

[SLKen]

I know this may sound a little silly however, on the R170 there is a method for re-setting this light. Turn the steering wheel full lock left and then full lock right.

Don't know if it is the same on other models

[pist nbroke]

^^Yeah, this is to re-initialise the steering angle sensor.

Usually need to do this after the battery has been disconnected, but wont actually fix a fault if there is one.

[SLacKer]

Give the reset a try as it could have been a weak battery all along and of course it was replaced so it was disconnected. It costs nothing to try and it may sort it out. Happens in my SLK as well if the battery has gone a bit flat.

[lotus160sport]

Thanks guys tried this but it is still coming on, the indy thinks it could be something to do with the brake booster servo as the light comes on when the brake pedal makes a clunk after pulling away, and he is also looking into the yaw sensor, I will let you know the outcome thanks again.

[Rat_Fink_67]

Sounds like a possible BAS diaphragm travel sensor fault, especially with the "clunk" you describe on the brake pedal. This would register a fault code though, I take it your indy has got STAR diagnosis and DAS?

[lotus160sport]

Rat_Fink_67 said:

Sounds like a possible BAS diaphragm travel sensor fault, especially with the "clunk" you describe on the brake pedal. This would register a fault code though, I take it your indy has got STAR diagnosis and DAS?

He sure has but it hasn't registered as the light doesn't come on and stay on, when I switch the engine of it disappears and then doesn't come back for a day or two it just doesn't seem to register on the computer I was with him in the car and we drove it whilst plugged in but all the sensors, yaw sensor etc just read normal with no fault codes after coming up it's a weird one. So as we can't get a definitive answer yet as it won't register the fault am going to see if it developes he thinks it is possibly either the brake booster servo or the bas module and both are pretty pricey so I shall wait and see.

[pist nbroke]

Rat_Fink_67, no fault code current or stored, What you reckon?

Had this before with intermittent EML's, bur rare for a BAS/ESP light not to record a code on a car of this vintage in my humble opinion.

Intermittent short circiut or CAN/ECU fault possibly?

P-S, ever had any of you customers raplacing their brake light bulbs with the wrong type? this could bring up ESP lights on the old sprinters etc.

[lotus160sport]

P-S, ever had any of you customers raplacing their brake light bulbs with the wrong type? this could bring up ESP lights on the old sprinters etc.

[/quote]

Hmmmm well as it happens about 2 months ago my brake bulb was working intermittent so changed the bulb but it kept doing it, turned out that the circuit on the light cluster had a short and couldn't be re soldered so bought a new cluster from Mercedes, it came with no bulbs so put the old bulbs back. Now the brake bulb I bought from halfrauds took a while to find as the one they had listed in the book wasn't the right one so had to find one that looked exactly the same, it has worked fine but makes me wonder if it could be something as silly as that bringing the light on maybe the bulb isn't quite right! On a plus sign the light hasn't come back on since yesterday after having the car plugged in again, maybe it's an electrical gremlin that will disappear fingers crossed, need my traction and abs if things are going to start getting slippy in the snow!!!

[Rat_Fink_67]

pist nbroke said:

Rat_Fink_67, no fault code current or stored, What you reckon?

Had this before with intermittent EML's, bur rare for a BAS/ESP light not to record a code on a car of this vintage in my humble opinion.

Intermittent short circiut or CAN/ECU fault possibly?

P-S, ever had any of you customers raplacing their brake light bulbs with the wrong type? this could bring up ESP lights on the old sprinters etc.

Hmm weird one that, like I mentioned earlier, with the pedal "pulse" I was inclined to think it was BAS travel sensor as I've experienced similar symptoms for that fault, but that always leaves a fault code so it's an odd one. I did have a W210 not long back bringing on the BAS/ESP light with no fault code, that turned out to be a corroded N/S/R wheel speed sensor ring that was opening up intermittently and causing spurious readings as it turned out, but that didn't cause the pedal issue. It's very odd not to record a fault code. It could well be a CAN/ECU fault yeah, maybe a moisture/corrosion issue causing intermittent acivation of the system and/or light without there actually being a "fault". I've had that recently with a front SAM on a W230.

I've not known the bulb issue, usually it just brings on the bulb light in my experience if the current draw is wrong.

The symptoms seem to be more "BAS" than "ESP" and I've never known W210's to be prone to ABS faults really bar the usual speed sensors but they leave fault codes, so maybe it is servo related, possibly BAS travel sensor after all causing the brake assist to trigger momentarily?