MB Medic Mercedes-Benz Repair Guides, Service, How To DIY
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In this guide (6 sections)
The video in this article will help you reset the service reminder on your Mercedes-Benz SLK, chassis R170. This is also called the FSS Service reset, and should be done after every oil change.
Models: SLK320 SLK230, SLK32 AMG Years: 1998-2004
How do you reset the oil service light on the Mercedes-Benz SLK
To reset the FSS System on an SLK R170 after an oil change, follow these steps:
- Turn the ignition to the ON position. That is position II, right before starting the engine.
- Within one second, press the knob/button twice.
- The present status for days or distance is displayed. Within 10 seconds, turn the key to OFF/LOCK. Picture below.
- Press and hold the knob or button until the distance is displayed again.
- Move the ignition to the run position again.
- Continue to hold the knob/button.
- After 10 seconds, a signal sounds, and the display shows 7,000 miles or 11,000 km for 10 seconds.
- Release the knob/button.
- Turn the ignition off and start the engine to verify the indicator has been reset.
A reset is not a service
Worth saying plainly before the procedure, because the two get confused. The button sequence above resets a counter. It does not change anything mechanical, it does not know whether oil came out of the car, and it will happily start counting down again from full on old oil. The reminder exists to prompt the work; clearing it without doing the work just removes the prompt.
The counter also assumes the oil the car was designed for went back in. FSS is counting down an interval that was calculated for a particular grade and specification, so the figure it gives you afterwards only means anything if the oil matches what the owner manual asks for.
Why the number it gives back is not always the same
This is the part owners ask about most. FSS stands for Flexible Service System, and flexible is the operative word: it is not a plain mileage countdown. It watches how the car is actually driven, which is why the display in step 3 offers days as well as distance, and why two identical SLKs can show different intervals.
Short trips, cold starts and hard use shorten it. Steady longer runs stretch it. So if the figure that appears after a reset is not what you expected, that is the system working rather than failing.
If the button sequence will not take
The timing is tight and that is usually the reason. Two presses within one second, then the key off within ten seconds, then the button held through the ignition coming back on. Miss any of those windows and nothing happens, with no error to tell you why. Most failed resets are a second or two of timing, so the first thing to do is simply try again, deliberately, with the steps in front of you.
If it still will not take after several careful attempts, the reset can be done directly through the instrument cluster with a scan tool rather than through the button sequence. The YOUCANIC UCAN-II Pro performs service resets on these cars, and because it also reads the cluster and the body modules, it tells you whether the cluster is simply ignoring the sequence or has an actual fault stored against it.
When the cluster itself is the problem
There is one failure on cars of this age that makes the whole question moot: the instrument cluster display losing segments or pixels, so the service figure cannot be read at all even when the reset works perfectly. It is a known age related failure rather than anything you did.
A replacement cluster has to be coded to the car and carries the mileage question with it. A board level repair of the original does not, so the cluster that comes back is the one that was always in the car. Module Medics repair instrument clusters at board level.
Related reading
Before you buy parts, scan every control module, not just the engine. It shows the root fault behind the warning lights and tells you whether the problem is still active. See how to do a full health check.
