For some time now, the ABS light in my 94 E420 has been coming on in an intermittent fashion. It usually occurs after I have been driving for 20 minutes or more, and does not seem to correspond with applying the brake pedal. I'll just look down, and it will be shining brightly.

I assume that one or both of the ABS sensors are sending erroneous signals, which triggers the light, but just want to make sure there are not any other causes for the light to come on before I drop a big chunk of change for new sensors.

Thanks in advance for any helpful suggestions.

I think the OVP can trigger the light if faulty as well. Check the fuse, or fuses, on the OVP too, might be blown (the fuse(s) in the OVP are the only blade type fuses I've seen in a Benz).

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Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.

There is no OVP on the V8 engines, if I am not mistaken. Is there anything else which can trigger the ABS light, other than the sensors?

If I recall correctly, there is no OVP on this model.

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)

Have the charging system checked. The ABS system requires high voltage values to operate properly, and a drop in voltage will cause the ABS light to come on.

It sounds like your alternator might need repair.

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John Shellenberg
1998 C230 "Black Betty" 240K

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There actually is a fuse in the computer box, I assume your E420 uses the same as my 92 400E.

That fuse (F1) protects the ABS module and throttle control unit (cruise control), if that fuse is burnt, ABS won't work, you will have ABS warning light all the times, cruise control won't work and engine rev won't pass 5500 rpm, I had all these problems on my 400E, replacing that fuse cured all.

Since ABS warning comes on intermittently, I would guess FUSE is OK, cleaning the ABS sensors will be the first thing I would suggest, also it's a good idea to check the battery voltage at idle, it should increase after you start the car, from something arround 12.3 to 12.8 Volt.

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99 BMW 540i 6-speed 110K Km
03 SAAB 9-5 wagon 80K Km
92 400E (Sold) 245K km
Still missing the days with the Benz, it kept me busy.

Thanks for the tips. Unfortunately, the ABS is intermittent, although my cruise control can also fail intermittently, so it may be worth while to change out the fuse either way to make sure, particularly since the light can come on without any obvious provocation. I have already cleaned off the sensors, which were quite dirty, but this did not seem to help. Other than the fuse, is there anything else I should consider before swapping out the sensors? Thanks.

By the way, did you mean a fuse in the fuse box, or a separate fuse where the computer sits on the passenger side?

It's one of the fuses on base unit in the computer box as you mentioned. you need an Allen wrench to open the box, there are 4 10 Amp fuses (3 if no ASR option). F1 is the first one counting from left if you stand in front of the car.

Can't remember what other fuses do, you might also pull out them and check.

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99 BMW 540i 6-speed 110K Km
03 SAAB 9-5 wagon 80K Km
92 400E (Sold) 245K km
Still missing the days with the Benz, it kept me busy.

I've experienced this problem several times. Every time it was an indication of a charging system problem. Have it checked.

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John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif

Well, I had the mechanic check the charging system, and it read a steady 14.4 volts. When he put a load on the system, the ABS still did not kick on. He is getting a new sensor reading tool today which does a thorough check of all of the electronic sensors, which may tell me what is going on. I'll keep everyone informed.

My independent MB mechanic just purchased another piece of diagnostic equipment which monitors all of the circuits in the car while rolling. Finally, he was able to isolate my ABS problem to the driver's side ABS sensor. He replaced it last night, and so far, no more ABS light. I am planning on bringing the car back in to have him run through all of the systems, since I still have a very intermittent, very strange idle problem which thus far has gone undiagnosed.

Despite my mechanic's best efforts thus far, the ABS light still comes back on, albeit on a less frequent than before basis. To date, this is what my mechanic has done:

1. Cleaned both front sensors;
2. He checked the charging system:
3. Replaced both front sensors, and cleaned the rear sensor.

His diagnostic equipment suggested that the front left sensor was bad, but it continues to come on with the new sensors. He believes that there must be a short in the system somewhere.

After he does a repair, I drive the car around for a few days to see what, if any, difference there is. As noted above, the ABS light does not come on as frequently as before. Also, when it comes on, it stays on until I stop and re-start the car, at which time it resets. It seems to come on at low speeds, such as city driving, and very rarely at highway speeds. Is there anyone out there who has experienced this type of ABS light behavior?

By the way, after charging me for one front sensor, my mechanic has basically told me he will continue to work on the car for free until this problem is solved. I have been working with him for well over a year, and know that he is not ripping me off.

As mentioned in an earlier post, there is no OVP in the E420. Also, I replaced all of the fuses, both in the fuse box and the ABS/Cruise brain, but it still comes on from time to time. Any other suggestions?

in your car. Check my web page under menu #8 to see what it does. Also ABS Module, menu #10.

Use a scanner to read codes in those two modules.

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Regards . . . . JimF
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'94 S500 Cpe

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