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Matt, Engineer
Category: Mercedes
Satisfied Customers: 22001
Experience:  Mechanical Engineer with 23 years experience in the auto industry, 8 yrs in formula 1 engine testing
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I have a Mercedes 1995 SL500. My problem is that whenever I

Customer Question

I have a Mercedes 1995 SL500. My problem is that whenever I go over 60mph my ASR light comes on and the car slowly decelerates to 0mph and I have to pull over and turn the car off and start it again
Submitted: 2 months ago.
Category: Mercedes
Customer: replied 2 months ago.
My uncle told me it may be because the tires are different sizes, but if not, what else could be the problem? And how much would it cost to fix? Also, if the Benz logo on the back of my SL500 fell off, can I get it replaced at a local Mercedes Benz dealer?
Expert:  Matt replied 2 months ago.


If your front to rear overall wheel size is more than 2.5% difference then yes this will trigger the ASR and it will cut power as the system is fooled into thinking you're in some kind of power slide

and with ABS / ASR systems a lot of 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.

also with mercedes

If the battery has been disconnected then it is necessary to perform a zero point calibration of the steering angle sensor. To do this you need to start the car and turn the steering wheel all the way to the left and then all the way to the right 5 or 6 times