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Discussion Starter #1
Hi there, hope somebody can help.

My ABS light on my 190e is turning on after 3 - 5 seconds driving. The car is responsive and doesn't seem to have any less power. The problem appeared after the car was left outside for a week (its always usually garaged).

Anyone able to help me diagnose the issue?

Cheers
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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The speed sensors on either the front or back wheels must not be working.
That would be my initial guess.
 

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Discussion Starter #3
The speed sensors on either the front or back wheels must not be working.
That would be my initial guess.
Thanks for the reply. Where on the inside wheels are these located? Anyone have a pic I can reference when I jack the car up?
 

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89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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I do not have picture but you can't miss them. When you take the wheel off, they are white in color (when new) and they attach to the brake hub. For the front wheels they are in the rear of the brake hub assembly.

It is advised when you replace your rotors to also replace these. I do not know how to test them. They may or may not be your problem.
 

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I do not have picture but you can't miss them. When you take the wheel off, they are white in color (when new) and they attach to the brake hub. For the front wheels they are in the rear of the brake hub assembly.

It is advised when you replace your rotors to also replace these. I do not know how to test them. They may or may not be your problem.
Thanks very much. I'll take a good look tonight and post a picture or two if I find the issue.
 

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Yeah I am having this problem, too. I found that replacing my cracked and crumbling fluid level sensors caps on top of the brake reservoir helped. This is not that easy a task as the caps/grommets have to be snug on the posts and holding the sensor posts to push on the grommets may be a problem. Taking off the old grommets might be a problem too if older style that part of the cap might twist down into the reservoir. Now I got grommets that were a little oversized from Pelican Parts. So, I took 2 pieces of black electrical tape and poked holes in these and threaded these on the posts. I then took a little superglue and added some to the top inside of the cap and put these on the posts. The next day I gingerly tore off the tape. It seems to have worked that the sensors are kept high but air is still allowed to escape...like a fermentation lock for brewing beer or wine!

Charlane
 

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The front sensors were cruddy as hell with metal filings. Was quite interested to see that the front sensors were magnetic. Cleaned. Didn't make a difference and the light is still on.

The stator inside the where the front sensors read, looks rusty. Can i just spray some WD40 in there and rotate the wheel?

The rear one (which I haven't gotten too yet) looks to be sited in the rear diff.
 

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W201, W212, W221, & W222 Moderator
'84 Euro 500SE, '85 Euro 2.3-16, '51 Euro 170S, '97 Jeep Wrangler Sport, '15 G63 AMG
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The sensors themselves may be toast. The front ones are easy enough to test with a voltmeter set to measure millivolts. With the tires off the ground, you can rotate the tire for each sensor, and if the sensor is working correctly, you should get at some voltage registering on your meter.

You can probably test the rear unit this way as well, but I haven't attempted it. I too, have the same issue with the ABS light coming on shortly after moving, and I've simply lived with it as the brakes themselves function perfectly otherwise. It is on the ever-growing laundry list of things to resolve at some point. I've yet to test my front sensors myself, but I know from testing the sensors on other ABS-equipped vehicles that this will work.

ETA: Here's a good video on it:
 

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W201, W212, W221, & W222 Moderator
'84 Euro 500SE, '85 Euro 2.3-16, '51 Euro 170S, '97 Jeep Wrangler Sport, '15 G63 AMG
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I got the motivation to go and test the front sensors. I just left the meter to set the range automatically, and made sure it was set to AC. A good sensor should register ~.5V to 1VAC. The faster you spin the wheel, the higher the voltage.

Spinning as fast as I could, I got 1.034V on the driver's side, and just .05V on the passenger side. It would seem that's my problem child. I will see if I can trigger the ABS light my rotating just that wheel when the car is running, but I will do that in the morning.

Now, here is a bit of an issue... replacement sensors are astronomical if you can find them for sale. Not sure how much I'd trust a used unit, but I suppose you could test the sensors at the yard with a multimeter just the same.
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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When I replaced my rotors a couple of years back I also replaced the sensors. I remember them being like 20 bucks each at the dealer. I could be mistaken. How much are they now?
 

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W201, W212, W221, & W222 Moderator
'84 Euro 500SE, '85 Euro 2.3-16, '51 Euro 170S, '97 Jeep Wrangler Sport, '15 G63 AMG
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$20 for an ABS sensor?? I wish!

If you were to boldly go the AutoZone route, you're looking at $318 each for either side of the front, and $257 for the rear. Parts-geek, which isn't very trustworthy either, sells the rear for $237. RockAuto shows various options, ranging from $168 for a unit made by "Standard Motor Products" up to $308 for stuff made by NTK.

Running the part number for the left unit shows that FCPEuro carries Genuine MB units for $133. If they have them in stock, or can get them, they're by far the cheapest option AND genuine MB, but I'd probably call first before placing an order.

2015401517 for the driver's side.
2015401617 for the passenger side.
2015400017 for the rear.

ECS Tuning carries the rear for $454.

A quick check of eBay shows one used unit for $71, and several "aftermarket" choices for $200+

ETA: 2015402317 is another suitable part number for the rear unit, and ECS carries that one for $270. Not sure the reason for the price disparity, as both are marketed as genuine MB, and are the exact same part.
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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Ahhh, I'm confusing the brake pad sensor with the ABS sensor. Where is the ABS sensor? Anywhere near the break pad sensor.

Mine has not failed as of yet, so they must last a while.
 

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Discussion Starter #13
I got the motivation to go and test the front sensors. I just left the meter to set the range automatically, and made sure it was set to AC. A good sensor should register ~.5V to 1VAC. The faster you spin the wheel, the higher the voltage.

Spinning as fast as I could, I got 1.034V on the driver's side, and just .05V on the passenger side. It would seem that's my problem child. I will see if I can trigger the ABS light my rotating just that wheel when the car is running, but I will do that in the morning.

Now, here is a bit of an issue... replacement sensors are astronomical if you can find them for sale. Not sure how much I'd trust a used unit, but I suppose you could test the sensors at the yard with a multimeter just the same.
Both mine are reading .5V and 1050 Ohms. So they can't be the issue (or they've both failed at the same time which seems unlikely). I guess the rear sensor needs a looking at.

As an aside, does anyone else's ABS sensor look like this:
2620271
 

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Discussion Starter #14
Both mine are reading .5V and 1050 Ohms. So they can't be the issue (or they've both failed at the same time which seems unlikely). I guess the rear sensor needs a looking at.

As an aside, does anyone else's ABS sensor look like this: View attachment 2620271
Sorry to clarify, the engine bay end of the ABS sensor, not the end at the wheel...
 

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W201, W212, W221, & W222 Moderator
'84 Euro 500SE, '85 Euro 2.3-16, '51 Euro 170S, '97 Jeep Wrangler Sport, '15 G63 AMG
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Ahhh, I'm confusing the brake pad sensor with the ABS sensor. Where is the ABS sensor? Anywhere near the break pad sensor.

Mine has not failed as of yet, so they must last a while.
I figured you may have confused the two.

They sit on the back side of the spindle assembly. It's a magnetic sensor that works with the teeth on the hub itself. They can be removed to be inspected without having to remove the wheel.

Both mine are reading .5V and 1050 Ohms. So they can't be the issue (or they've both failed at the same time which seems unlikely). I guess the rear sensor needs a looking at.

As an aside, does anyone else's ABS sensor look like this: View attachment 2620271
To answer your photo first, yes, that is the connector for the ABS sensors.

You may also check out your OVP, and you might want to look at several relays that sit under the ABS pump cover.
 

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Discussion Starter #16
I figured you may have confused the two.

They sit on the back side of the spindle assembly. It's a magnetic sensor that works with the teeth on the hub itself. They can be removed to be inspected without having to remove the wheel.



To answer your photo first, yes, that is the connector for the ABS sensors.

You may also check out your OVP, and you might want to look at several relays that sit under the ABS pump cover.
I'm pretty sure my OVP is okay as wouldn't my performance be shot?

In regards to the ABS pump cover, is that this or the one below? Thanks for helping a rookie.
2620272
2620273
 

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W201, W212, W221, & W222 Moderator
'84 Euro 500SE, '85 Euro 2.3-16, '51 Euro 170S, '97 Jeep Wrangler Sport, '15 G63 AMG
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OVP electrical issues are honestly difficult to pinpoint sometimes, as everything else will appear to be fine... electronics are funny like that.

The cover on the pump in the engine bay, so the first photo. You'll find several relays underneath that cover, and often times when a relay is toast, it'll manifest itself as a light. However, given that the light turns on AFTER you begin to move, I'm still leaning toward a sensor.

In a few hours, when the rest of the neighborhood wakes up (my 16V isn't the quietest, to the point where I'm pricing stock exhaust components just to be done with it again), my plan is to prop the entire car up, start it up, and then spin each wheel to see if any of them cause the light to kick on. Based on my measurements, the passenger side is toast, but being able to rotate it and cause the light to come on will also determine if rotating the wheels independently can be used a diagnostic method to further test the sensors. I'll probably just put the car into first and spin the tires in the air as to have both wheels spinning since the rear unit is a center sensor.
 

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Uh YEAH. So took off the wheels and took out the wheel sensors and cleaned the magnetic end and applied di-electric grease to the other end, this being the next best thing to soldering. I opened the ABS unit under the hood and popped 2 relays and one connector and applied do-electric grease there sparingly to the pins so no continuity between these. My brakes were spongy and I decided to bleed the air out of the system because with the grommets missing the chance of air increase was possible. I had went to the junkyard and got some excellent front and rear rotors, that almost all front and rear rotors for all Mercedes appear to be the same regardless of year and model which was just great that I tapped some from newer models. I found I did not need these however. Before I attached the grommets to the sensors on the reservoir my ABS light was on constantly and I believe it was because the sensors were "sinking". No ABS light now. Just sayin'. I do not "throw" parts at my car wracking up a loss of $.

Charlane
 

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One thing I do know is that the abs sensors/circuitry are very precise and therefore are very sensitive to speed. Even a ~3mph difference in speed between rear and front sensors can trip that circuit.
 

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Just as a reference point, both of my W201s also have their original ABS sensors and they're working perfectly fine. I should go ahead and clean off the magnetic stuff that gets stuck to them though.
One thing I do know is that the abs sensors/circuitry are very precise and therefore are very sensitive to speed. Even a ~3mph difference in speed between rear and front sensors can trip that circuit.
I've seen this in action when the car is on the smog dyno. ABS always lights up.
 
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