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  #1  
Old 05-29-2006, 12:20 PM
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Help. ABS light on C280. Here are some clues for you experts.

Hey all. Need your help please. Wifey reported that the ABS light came on my family's grocery-getter (a very clean and tight W202 C280). Went out and checked. Here are the symptoms. Maybe you can help me fast-track the problem:

* Put key in. Foot on brake pedal.

* Twist key to position #2 (pre-start). All idiot lights come ON.

* Twist key to position #3. Engine starts instantly. All dash lights go OUT.

* Foot OFF the brake pedal. ABS light comes ON instantly.
(Note: if I start the engine with foot OFF brake pedal, ABS light does not go OUT.)

* Drive the car. Everything works, including brake lights ... except CRUISE CONTROL.

* Checked battery connections, brake fluid, fuses, then inspected (but did not replace) front wheel sensors, brake pedal switch, rear differential speed sensor, multi-pin connectors in trunk. Unplug, inspect, plug back in. All look clean and tight. Test drive. No change.

* Note: the same day the ABS light came on, Wifey says the driver's seat belt chime/warning stopped working. Is there a connection? Hard to believe, but I will also investigate a faulty/sticky seat buckle and the wiring under the seat.

Any ideas? Much obliged if you can share them. Thanks a million.


Last edited by RProsser; 05-31-2006 at 01:10 PM.
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  #2  
Old 05-30-2006, 11:47 AM
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PS: From what I have learned, the common culprits are:

1 - rear diff speed sensor
2 - front wheel speed sensor
3 - brake pedal switch

The first two are straightforward, but if the brake lights work, is the brake pedal switch okay? Seems a major hassle getting the old one out. The hood release gave me a lot of trouble.
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  #3  
Old 05-30-2006, 11:50 AM
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Location: Florida / N.H.
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You may also have a low voltage condition
Have the battery/changing system checked.
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  #4  
Old 05-31-2006, 01:07 PM
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Follow-up: I had the codes read by my local MBZ wrench. Apparently, the culprit is the brake light switch. Ugh, looks like a PITA to get to in the foot-well. And time I buy an OBDII reader!
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  #5  
Old 07-23-2006, 01:35 PM
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Hi. Thought you may be interested in / able to lend advice on my ongoing problem: an intermittent ABS light in my '97 C280:

Action 1: Two weeks ago I had a MBZ mechanic replace the brake switch. Actually, twice. First one was faulty! It got stuck in the "on" position. Drove it like that for 30 miles or more.

Result: Although the ABS is off when I start the car, it will comes back on a few miles later. It's not a repeatable problem, but sometimes it comes on after a stop sign/right or left turn.

Action 2: Last week I had the error codes read by the same MBZ mechanic:
- ABS: "C-1200 stop switch"
- Engine: "P1584 stop switch"

What? It's a new swtich in there!? The mechanic checked the switch and said it's working fine. Note: Since the first stop switch had been stuck "on" for a while, I changed all the brake light bulbs because of the excessive heat (one was black inside). Just a precaution in case a bad bulb can have an effect on the ABS system (a stretch, I know).

Result: Drove it all week ... same problem exactly. Looks good for a while, then it comes on. Typically while going slow and turning sharply. IS THIS A CLUE?

Action 3: Today, I changed both front ABS wheel speed sensors.

Result: Oddly, the light was on when I started the car this time. It went out after about 100 yards of driving. Then, as usual, a few miles later, while navigating the neighborhood streets, it back came on.

The question: Should I have reset the system when I changed the sensors? Do I keep moving, changing the REAR sensor next?

Thanks for any advice.
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  #6  
Old 07-23-2006, 02:06 PM
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Quote:
Originally Posted by RProsser

Action 2: Last week I had the error codes read by the same MBZ mechanic:
- ABS: "C-1200 stop switch"
- Engine: "P1584 stop switch"
If the fault codes for the Stop Lamp Switch re-occur, then the problem lies with the switch, wiring, or the control module. The wiring should be checked for short circuits to power, ground, and other wires. This is a simple job that only takes a few minutes. Don't waste anymore money until you check the wiring. Good luck
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  #7  
Old 07-23-2006, 02:15 PM
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<>

..specially the bulb sockets in the rear....common failure.
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  #8  
Old 07-23-2006, 02:55 PM
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Thanks gents. Checking the wiring for "common" problems is "simple," if you know where to look, what to check. Wish I did. I looked at the obvious items, i.e., corroded sockets, chafed wires, etc., but I've seen nothing out of the ordinary.

Now since the ABS light come on during slow driving, turning, braking, etc., I'd assume it has something to do with the brake pedal, as you two mention. Perhaps I will double check the brake light sockets. That's easy enough.

And thanks for all your help.

Last edited by RProsser; 07-25-2006 at 09:39 AM.
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  #9  
Old 09-07-2006, 12:27 PM
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ABS light problem fixed.

ABS light problem is fixed. Here's a review of my findings.

First Mercedes "specialist":

- First new brake switch installed was faulty. It failed thirty miles from home. I drove back not knowing my brake lights had been on the entire time (remember this part).

- Second new brake switch installed. Seemed to fix the problem -- for a while. Then the ABS light came on again. Same basic problem as before. Codes read "brake light switch." Weeks later I started getting a bulb warning light. Replacing the brake light bulbs turned it off, but the problem would surface in a few days.

The shop showed no real interest in helping further. They said: "Make an appointment next Thursday. We'll have to keep it for a few days -- maybe we can find the problem. Probably an ABS control unit."

New Mercedes specialist -- a real one:

- Called a new mechanic. "Hans" asked for me to come over immediately. Took the time and interest in the car. Spent an hour right then to read the codes, drive car, re-read the codes. It came up every time "Brake light switch." He put in a third new switch. I also mentioned the brakes lights had stuck on for thirty miles. We inspected the rear multi bulb housings very closely. They appear to have slightly warped/burned areas where the bulbs are held. Possibly this now causes a high resistance situation, hence a bulb out warning when there isn't one. We replaced both units and installed all new bulbs.

End of problem! I have driven the car for about 150 miles and all lights stay out.

The problem got complicated when the fist shop installed a questionably "new" first switch. I say this because they showed it to me before they put it in. The bag had already been opened. My sense told me it's not 100% new. It was just a hunch, but look at the result. Keep this in mind when your ABS light goes on and you think replacing a suspected part with new instantly solves the problem.
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  #10  
Old 09-07-2006, 12:35 PM
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<
End of problem! I have driven the car for about 150 miles and all lights stay out.
>>

Thread #7...........
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  #11  
Old 09-07-2006, 02:04 PM
david s poole
 
Join Date: Mar 2005
Location: dallas
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abs/brake light switch

i have posted several times on this forum that no one should buy an aftermarket switch.they are junk use only ones from dealer.your prolonged experience illustrates my point perfectly.but i'm glad yours is finally fixed.
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2000 Mercedes Benz C280
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  #12  
Old 09-08-2006, 02:44 AM
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How much are these sensors and the how long do the take as an DYI?
thanks
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  #13  
Old 09-08-2006, 10:25 AM
david s poole
 
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brake lite switch

they run about $17 from the dealer and the first time you do it it may take 1hr as the space is cramped and not conduisive to clean language.many of the guys on the dealer svc drive can do it in 10mins.i think my best is about 20.

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European Performance
Dallas, TX
4696880422

"Fortune favors the prepared mind"
1987 Mercedes Benz 420SEL
1988 Mercedes Benz 300TE (With new evaporator)
2000 Mercedes Benz C280
http://www.w108.org/gallery/albums/A...1159.thumb.jpg
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