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Matt, Engineer
Category: Mercedes
Satisfied Customers: 21604
Experience:  Mechanical Engineer with 23 years experience in the auto industry, 8 yrs in formula 1 engine testing
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The ASR light comes on & I have no accelerator pedal action,

Customer Question

the ASR light comes on & I have no accelerator pedal action , let it run for a few moments & re start & it usualy is fine sometimes I have to drive for a while before restart works . there is a ASR off switch which doesn't seem to do anything
JA: Just to clarify, what are the exact lights you're talking about?
Customer: the ASR light
JA: What is the model/year of your Mercedes?
Customer: 1995 sl 500
JA: Are you fixing your SL yourself? What have you tried so far?
Customer: I would like to fix myself havnt done anything as of yet
JA: Anything else you want the mechanic to know before I connect you?
Customer: that's it
Submitted: 9 months ago.
Category: Mercedes
Expert:  Matt replied 9 months ago.


if the ASR is being triggered by a faulty sensor then the car will be trying to reduce engine power to prevent the wheelspin it 'thinks' is occurring

However with ABS and traction control systems 99% of the time its a problem with one of the wheel speed sensors and I'd first check the connections at all four corners first for any signs of corrosion or chafed wiring.

The sensor is located in the wheel hub so you'll have to remove each wheel in turn to inspect them all.

Also check that the toothed wheel that the sensor points to is clean and free of any debris.

you can check each sensor's function by plugging the two output wires into an AC voltmeter and spinning the wheel quite quickly, you should get a voltage signal that increases with rev's.

Its possible that the fault is only a bad connection to one of the wheel sensors.

This may be remedied by removing each wheel in turn and unplugging each sensor and cleaning the contacts with a squirt of electrical contact cleaner. Then refitting.

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