4 Ways Your Mercedes Key Won’t Work

Why Isn’t My Key Working? (And What To Do Next)

How To Tell If The Issue Is In The Key, The Battery, Or The Car’s Electronics.

You slide into your car and insert the key—but nothing happens. Chances are you’re already running late somewhere. But is the key the problem? Or is it something else?

We’ve heard story after story about the hassles malfunctioning transponder keys can cause. Additionally, in newer Mercedes (1997 – current), certain security protocols can fail and also keep the car from communicating with the key.

Here’s how to determine the type of problem so you can take appropriate action.

Your Key Won’t Unlock The Car

If your Mercedes key has lost its remote function, such as unlocking doors or opening the trunk, the key’s own internal battery may be dead or dying. However, if this is the case, your key should still be able to start the car.

Your Key Won’t Unlock The Car, And Won’t Start The Car

It could be the car battery. If the car battery is dead, the key’s remote won’t be able to communicate wirelessly with the car at all. And to avoid the risk of damaging the electronics on your Mercedes, have the battery tested by a professional.

You Can Unlock Your Car, But The Key Won’t Turn Or Start The Engine

If remote functions on your Mercedes key do work and yet your car won’t start, this can still be a problem with your key.

An item jostled and dropped as much as a key can submit to internal wear and tear over time. This can cause the electronics inside the key to malfunction. Certain problems with the car itself can also cause the key’s programming to fail.

The Spare Key Doesn’t Work, Either

It’s always a good idea to have an extra key for your Mercedes. (Get one made if you don’t have an extra!) Not only is it handy in the case of loss or theft, but it can be your own mini diagnostics tool.

But if the spare key doesn’t start your car, the problem is likely due to other factors, such as an electronics issue with the car itself:


– Steering lock (common in C-Class, w204 chassis Mercedes)

– DAS (Driver Authorization System)

– ESL (Electronic Steering Lock)

– EIS (Electronic Ignition Switch)

– ME (Motor Electronics Computer)

But before you arrange to have your car towed to the dealership (or your trusty, factory-certified mechanic) for diagnostics and repairs, try getting your key tested. It’s fast, easy, and may save you a tow.