A Class W168 BAS/ESC light

Mercedes 190E

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Hi All

My Dad bought a W168 A class recently. A very nice car. One thing though-the BAS/ESC (Brake assist/stability control) warning light keeps coming on whilst he is driving. From what I can tell from the handbook, this means that they arent working....:shock: Followed the instructions about turning the steering from lock to lock which doesnt work. If it is turned off and restarted, the light goes out but then soon comes on again whilst driving.

It is under warranty, so he will take it back, but its always useful to know what the problem is likely to be when dealing with Merc dealers!
Any ideas as to cause very welcome!
;)
 

MB-Car-Tech

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John,

Obviously it needs a Diagnostic Test with the STAR.

Could be a few faults but common failures are the Brake Light Switch, Lateral Acceleration Sensor.

The Traction control system (ESP) is quite a sensitive little system and the fact the light comes on when driving could even point to a wheel speed sensor.

First point is... is the steering wheel in the straight ahead position when driving straight ???

if the car is straight and the wheel is offset then the ESP system gets confused as the steering angle sensor is in effect reading incorrect values as to what the wheels are doing. could be a mal adjustment of the tracking.

Get a STAR machine on it to start with and values can be read from there.

good luck!
 
OP
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Mercedes 190E

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  • Thread Starter
  • Thread starter
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Just to report back, the car went in to the dealer today-faulty steering angle sensor, replaced under warranty. :)
 

television

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Just to report back, the car went in to the dealer today-faulty steering angle sensor, replaced under warranty. :)

This could be a modified part John as many have failed, anyway pleased that it is all fixed
 

mattkh

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Could be a few faults but common failures are the Brake Light Switch, Lateral Acceleration Sensor.
Hi
Does the brake light switch failure then also mean that the brake lights will not come ON when the pedal is pressed ?
 

MB-Car-Tech

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mattkh,

the brake light switch has a dual circuit,

basically one side actuates the brake lights - never see this side fail

other side is for the CAN communication side -

NO normally open side

NC normally closed side

when pedal is depressed these must be seen to swap in position - if so switch is OK !!!

These values can be seen diagnostically

:D:D
 

mattkh

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Hi
Thanks a million everyone.
New brake pedal switch was the answer.
 


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