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Car Forum / Mercedes-Benz Cars / February 2005ASR malfunction
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 > 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. Were your tires sliding so much that the computer bus system got an overload? There are some error codes concerning the brakes with footnote: You can reset them if customer does not complain about disfunction. After my return from a greek island last summer there was an errorcode: >Rain sensor to hot< ;-)  SignatureRoland Franzius There was a lot of slipping and sliding and I assume that the ASR was coming on frequently. Could it just be something that is a residual error (from being overloaded as you mentioned) and only hits the malfunction light when ASR is applied again (but will clear over time - or how could I clear this code)? Are there any flash codes that this produces? >> 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 [quoted text clipped - 9 lines] > After my return from a greek island last summer there was an errorcode: > >Rain sensor to hot< ;-) > There was a lot of slipping and sliding and I assume that the ASR was coming > on frequently. Could it just be something that is a residual error (from > being overloaded as you mentioned) and only hits the malfunction light when > ASR is applied again (but will clear over time - or how could I clear this > code)? Are there any flash codes that this produces? The brake assistants will be blocked if the bus system cannot answer control requests in time. The block stays until a reset happens mostly doe by a new start of the engine. Error code marks will be cleared at the next regular service. You need a laptop and the MB assist interface to clear the error codes. If there is no error light just wait. -- Roland Franzius In my case the ASR Malfunction light now comes on whenever the rear wheels slip. It does not come on when the engine is first started, and so far does not appear during normal (no slipping) conditions. This started yesterday. >> There was a lot of slipping and sliding and I assume that the ASR was >> coming on frequently. Could it just be something that is a residual [quoted text clipped - 14 lines] > > Roland Franzius > In my case the ASR Malfunction light now comes on whenever the rear wheels > slip. It does not come on when the engine is first started, and so far does > not appear during normal (no slipping) conditions. This started yesterday. Ah you mean the regular slipping warning light. Thats normal. May happen even with full throttle on a wet road. But check tires profile and pressure. SignatureRoland Franzius No - the malfunction light comes on once the wheels slip.... > Ah you mean the regular slipping warning light. Thats normal. May happen > even with full throttle on a wet road. But check tires profile and > pressure. You probably just need to have those sensor cleaned... after all.. it is all gunked up by brake dust. Where do those sensors reside on the rear discs, and can I just shot them with some brake cleaning fluid? > You probably just need to have those sensor cleaned... after all.. it is > all > gunked up by brake dust. Just follow the wire... not the one to the brake pads... but the other one. Yes, just shoot it with brake cleaner. >No - the malfunction light comes on once the wheels slip.... And stays on after the wheels stop slipping, yes? There seems to be some confusion here. The light comes on when the wheels first slip and stays on untill you power cycle the car... There are two different indicator lights involved with ASR. One is the triangle on the top of the speedometer that indicates that ASR has been activated (due to wheel slippage) and the other is malfunction indicator along the bottom of the instrument cluster. It is the latter (the malfunction indicator) that stays on *after* wheels have slipped. Josh >>No - the malfunction light comes on once the wheels slip.... > > And stays on after the wheels stop slipping, yes? There seems to be > some confusion here. The light comes on when the wheels first slip > and stays on untill you power cycle the car... Maybe a dumb question but...... do you have snow tires on the rear that are bigger in size than the tires on the front? > There are two different indicator lights involved with ASR. One is the > triangle on the top of the speedometer that indicates that ASR has been [quoted text clipped - 9 lines] > > some confusion here. The light comes on when the wheels first slip > > and stays on untill you power cycle the car... Nope. They are all the same size. > Maybe a dumb question but...... do you have snow tires on the rear that > are bigger in size than the [quoted text clipped - 13 lines] >> > some confusion here. The light comes on when the wheels first slip >> > and stays on untill you power cycle the car... Air pressure all the same? Common ASR fault is Brake Lamp switch. Air pressure looks good, and the brake lights (so I'm assuming the brake light switch) work fine. Could a bad brake light cause this type of fault? The reason I ask is that I had had a brake light failure at about the same time as the ASR malfunction. Note that the ASR malfunction indicator does not come on unless the wheels slip (under normal conditions it stays off). > Air pressure all the same? > Common ASR fault is Brake Lamp switch. 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. > 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 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 SignatureLettuce spray for whirled peas... 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. >>The ASR system on your car stores pressure in a gas sphere. The pressure >>is [quoted text clipped - 8 lines] > 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 >>The ASR system on your car stores pressure in a gas sphere. The pressure >>is [quoted text clipped - 4 lines] > 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) 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. Signature- RODNEY >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. 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? SignatureLettuce spray for whirled peas... >>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 [quoted text clipped - 3 lines] > 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. Signature- RODNEY |
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