hello everyone, I hate to keep beating a dead horse but here goes. I have ASR and ABS lights on and I don't have the limp mode issue like others with ASR light on. My car runs fine I can go triple digits in my 97 S500. I KNOW THE BEST WAY TO find what the problem is to check codes, but before I do that, I want to replace the stop light switch in the brake peddle first, then if needed I will clean or replace the ABS speed sensor. if both will not remedy the problem then I am in for some serious $$$$$$$$ repair? I read in the thread that the way to test a broken stop light switch is to press on the brake peddle , then start the engine and wait for a few minutes =, then let go of the brake peddle. If the asr and abs lights come on after you do that, then the stop loght switch needs replacing. Can anyone verify this information. I have followed these proceddures and it seems correct. If I start the car without having pressing the brake peddle, then the light would turn on immediately. I search every thread relating to asr abs and could not find the information I have read earlier. I just want to know if there is a way to check a broken stop light switch.

I believe there is a fault code for bad brake lamp switch - there was on earlier cars. I have always just replaced it - it's like a $15/15 minute item.

Shot gunning the brake light switch is not such a bad idea as they are cheap and fail regularly. There are FOUR speed sensors and they aren't exactly cheap, and they are only one possibility of what your problem could be.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

I will order the stop light switch soon and share my result in a later post. thnaks

There's a good chance it will be the brake light switch. I had the exact same symptoms as you... replaced the switch and presto, issue solved. Hardest part is getting the lower panel off the dash so that you can get to the switch. There are two catches at the front of the panel that are tricky to release unless you know where they are... so here's a picture of S500 when I took it apart... the front clips are circled in red and are hidden when the panel is in place. You release them with a fine tip screwdriver put between the carpet on the lower panel and the dash.
Also, length of the switch plunger is "automatic" in setting. Be sure to pull it out before installing. First time you step on the brake, it will adjust itself to the right length.
Hope this helps.

Attached Thumbnails

 

__________________
KenP

1996 S500 W140 Coupe

Ken,
I had the exact same problem with my 93 400e (sold it last month) which had about 140k on it when the ABS & ASR lights came. It never went on the 'limp home' mode. It drove great but the braking went to a 'manual mode' meaning - the ABS wouldn't kick in. The braking was just fine. The mechanic said it needed a new 'ASR pressure pump'.

smk_texas
98 S420 50K

Thank you Ken P for the pics, that would help indeed. I ordered the part, and will try to post DIY photos for everyone at this forum to see. Once again thanks Ken.

Hello Ken, So didyou ever replace the asr pump?

You're most welcome for the pix. Once you get that lower panel off, the rest is very straightforward. There are a number of screws holding the panel, most of which are evident. Do a search on this forum and you'll find a pix I posted a while back on where all the screws are. Removing this panel is one of the classic jobs on the W140 in that it will take you a fair amount of time the first time you do it... after that, its only a minute or two.
I think the odds are in your favor that its the switch and not the ABS pump. As Steve said, they're a known failure item on these cars. The good news is that they are inexpensive and easy to change. Ordinarily the folks (especially Steve) on this forum would recommend against simply guessing to replace a part, especially on a W140 car. You can go broke aiming in the dark. In this case, I think its entirely worth the small expense and the odds are pretty good you'll solve your problem. Be sure to extend the new switch plunger before you install it.
Besides, you'll have the "opportunity" to learn something about your car that you didn't know before.
Good luck. Let us know the results. Lots of folks here willing to help.

__________________
KenP

1996 S500 W140 Coupe

i am stuck in LHM. maybe i should replace this too? and in a S600 would it be the same?

wow. do i have the same problem.my asr lights and the brake wear indicator came on the other day. i thought it meant my pads were low but i haven't had the time to fully investigate. i took my right front tire off and the pads looked great--lots of meat. i haven't had time to check out the others but could mine be the switch as well? ken your thumbnail didn't show up for me , could you email me the pics, please? thanks

__________________
'95 s500 (bought for wife but can't bear to share!!!) 125kms
'92 legend 180kms
'88 tbirdturbo(fantastic car-only regular maint.)120kms
'87 mustang gt(gone)
'86 tbirdturbo(gone)
'85 mustang gt(gone-but not forgotten)

Hello,

Yes the ASR pressure pump was replaced. In your case I am not too sure because your ABS seems to be fine. In my case my ABS wouldn't kick in.

smk_texas
98 S420 50K

daddiojiggy, happy to send you pix. Sent you a PM.
Your 95 may not have these clips. Earlier cars appear to use all screws. Manual I have showed screws in multiple places. I just about went nuts trying to figure out what was refusing to let the panel loose after the screws were all out.
This may be one of the many changes they made between 95 and 96. Won't take you long to find out.
Meanwhile, I've attached a couple of close up shots, one of each latch.
Also, pix of mating loop on one side of the under dash panel.
Hard to show much fine detail within the bandwidth restrictions for posting.
Hope this helps.

Attached Thumbnails

     

__________________
KenP

1996 S500 W140 Coupe

more pics

Attached Thumbnails

 

Benzsu-
Did you change the switch? Did it fix your problem?

__________________
KenP

1996 S500 W140 Coupe