While driving in the snow/ice yesterday the ASR malfunction light came on in my wife's '95 E320. What are the possible causes and are there any ways to diagnose it w/o taking it to the shop? The light clears after restarting the car and driving on roads that there is no snow/ice.
Josh
The ASR system on your car stores pressure in a gas sphere. The pressure is kept within a working range by a charge pump. Whenever ASR activates, some of the pressure is lost as the spinning wheel is braked. The pump then activates to re charge the pressure. If the pump operates more than 10 times in a journey, it assumes there is a leak in the system and shuts down. Can't remember if it needs to be reset by an MB dealer or just by turning the ignition off/on.
Sorry, but none of the above is correct, as it actually refers to the SBC braking system found on the latest E class. (211 chassis)
Are we talking about a 124 or a 210 E class? If it's a 210 (first 3 numbers of chassis number) then far and away the most likely fault is the brake light switch, which is cheap and easy to change yourself
No! If the car had SBC then it would have ESP and not ASR1, ASR11 or ASR111.!!! ASR1 and ASR111 were Blink Testable. ASR11 was not. ASR1 had a separate ECU, Charge pump and Pressure sphere. Also the NO/NC contacts of the Brake light switch would fail on dry roads as well as the slippy stuff. Not to mention the fact that the ASR Malfunction light comes on during "Brake Torque Control" (wheel spin) and not during a braking situation.
That's not true. All vehicles that have any form of traction or stability control must have a pressure reserve in order to activate the hydraulic brakes without the driver having to depress the pedal. The SBC system takes it a step further and uses this pressure reserve in normal braking, so that instead of the brake pedal mechanically controlling the master cylinder, its motion is interpreted by a computer than in turn releases the pressure reserve to active the hydraulic system.
Sure, but don't Mercs use the ABS pump for this purpose, with ASR simply existing as a control unit which communicates with the ABS pump/engine control unit when required?
ABS does not use a pressure reserve for its function. It uses valve(s) to pulse the hydraulic force created by the brake pedal when wheel spin is detected. ASR uses the same valve system to "pulse" the brakes in order to prevent wheel spin, but requires the pump and pressure reserve so that the system can be activated without pressure from the pedal. With the addition of this pressure reserve for ASR, BAS can be implemented. BAS detects an emergency braking situation based on the speed and force of the driver's foot on the pedal, and then it release the pressure reserve. This applies much more force more quickly than could be done by the driver. Of course when BAS is activated, ABS is still able to reduce skidding, helping to maintain vehicle control. ESP uses the same pressure reserve to selectively pulse the brakes when an oversteer or understeer situation is encountered. Finally, ETS uses the same system to keep a tractionless wheel from "stealing" all the torque on the open differentials on the all-wheel drive systems.
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