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Old 10-01-2012, 01:29 PM
Join Date: Aug 2006
Posts: 6
ABS BAS ASR indicators on 1998 C280

I will be as concise as possible in outlining the history behind my question.

The vehicle was out of service for about 2 months, during that time the rear wheel bearings and brake pads were replaced and the front wheel bearings pads, tie rod assembly, lower ball joints and pads were replaced. All sensors and hubs were checked for damage and cleaned, all wiring connections were double checked for security.

Upon putting the vehicle back into service all systems indicated clear via the instrument panel. The brake pedal felt soft with the engine off and also when the engine was initially started. At the time I attributed this to the initial repositioning of the brake pistons with the new pads.

While exiting the gravel drive the triangular ASR indicator came on as expected when the rear wheel spun, on the next application of the brakes the BAS, ASR, and ABS indicators came on and have been on since. The ASR warning lamp does not come on when the rear wheels spin and there are no rear wheel brakes. (Both rear wheels spin freely on a grass surface while holding the brakes on and bringing the RPM above 1500 while in drive)

The Bentely manual suggest that low battery voltage could cause triggering of the indicator lights. The negative battery cable was lifted and the battery charged at 15 amps, it took 2 hours to get the battery to full charge. The cable was reconnected and the vehicle started and driven but the indicators are still on and the rear brakes not working.

Under traditional pre-ABS diagnosis I would replace the master cylinder, no rear brakes, spongy pedal, brakes pump up some but still don't work on the rear. I am not knowledgeable enough with regard to the exact workings of the ABS system to know if an error in it would prevent engagement of the rear brakes. If I had a suitable pressure gauge and fittings I would check the master cylinder at its discharge ports.

My questions are: Is the master cylinder a prime suspect here and if it is bypassing in the rear section will the installation of a new cylinder restore the functioning of the BAS ASR and ABS and turn off the fault indicators?
Can any ABS faults be located with an OBDII reader or are they all in the domain of the factory tool?

Sorry for the length of the post.

T W Hudson

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Old 10-01-2012, 01:45 PM
Join Date: May 2005
Location: CALIF
Posts: 508
abs light on

E320 abs light on, replace the brake light switch under the driver dash,the dealer
will charge 2 hrs dia, plus sw and labor, the car was a 2001 E320
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Old 10-01-2012, 01:47 PM
Registered User
Join Date: Jun 2012
Posts: 228
You won't see anything with a generic OBD scanner. You need a MB tool for that.
Don't touch the Master Cylinder, it's unlikely that's the cause. I would suspect the ABS sensors at the wheels, since that is what they played with.
You really need someone to read the fault codes in the BAS and ABS modules. If you skip this step, you will spend more time/money on trouble shooting

The brake switch may be your fault, except that the lights came on after you had your brakes/suspension serviced. Why wouldn't you go back to the guys that serviced it and get it scanned at their expense ?
Where are you located ?

Another cause may be Air in the Hydraulic ABS pump. If the guys that serviced your car, disconnected the brake lines and did not perform the proper bleeding procedure, than that would cause the Pump to deliver insufficient pressure on the rear lines
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Old 10-01-2012, 08:38 PM
Registered User
Join Date: May 2006
Posts: 140
possibly needs reset

granted, my 2002 E320 could be entirely different;
After my battery has been disconneted, all of thoses lights come on when re-connecting the battery. I called the dealer about an appointment for the lights. They asked if I had changed a battery. 'yes'. The dealer tech then described the reset proceedure, which was something like turn the steering wheel full right, then full left. You might inquire about this.
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Old 10-04-2012, 12:36 PM
Join Date: Aug 2006
Posts: 6
I did the bearing and pad replacement and no hydraulic lines were opened. I will be going back and checking the sensors and wiring for continuity.

Will get it to the local dealership and get it scanned properly before proceeding much further.

Thanks for the input.
T W Hudson
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Old 10-04-2012, 12:38 PM
Join Date: Aug 2006
Posts: 6
Thanks, I will check into this.
T W Hudson

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