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Causes & Solutions: Mercedes Turn Key Nothing Happens

Causes & Solutions: Mercedes Turn Key Nothing Happens

You’re ready to go hit the road then you get yourself into a “Mercedes turn key nothing happens” situation. You unfortunately can’t start the car. So what could be up? It could be a simple fix or a greater problem. It could be as simple as a locked steering wheel or as complicated as an Electronic Ignition Switch issue that needs to be replaced. Hopefully you’ll get an idea what you are dealing with through this article.

Auto Repairs Are EXPENSIVE

Mercedes Turn Key Nothing Happens: Common Reasons


The common main reason for the “Mercedes Turn Key Nothing Happens” situation is a dead battery. But before settling down with that conclusion there can also be several other issues worth looking into. When you insert the Smart Key remote into the Electronic Ignition Switch (EIS) control module (N73), the induction coil ring in the EIS supplies power to the key. 


The Drive Authorization is then validated by exchanging data with the infrared transmitter.  A number of issues could arise with these components or during the whole process of this operation. Let’s take a look at those:


Issues with Mercedes EIS/EZS Immobiliser Key Module


Common Symptoms: 


  • Inability to turn the key
  • Inability to start the car
  • Key Turned but Car refuses to start
  • Issues with the Ignition Key


The Mercedes Immobilizer system's Drive Authorization System (DAS) tests drive authorization every time you insert the key into the ignition and try to start the vehicle. DAS was first released in 1996 and has since undergone many security upgrades. DAS 2, 2A, X, and 3 are the most common DAS models.


Locked Steering Wheel


New drivers always have an issue with this. So if you’re a new driver and you’re in this “Mercedes turn key nothing happens” situation you might only be dealing with this very fixable issue of a locked steering wheel. The steering column lock is a safety device that all automobile manufacturers have in their vehicles.


 If you can't get the key to turn in the ignition, try rotating the steering wheel while turning the key. If you try to turn the steering wheel in one direction, it may feel fully solid and will move slightly in the opposite direction. Insert the key and try to turn it again after turning the steering wheel in the direction that makes a little movement. You can use your hands to apply pressure to the steering wheel, or you can shake it. Insert the key into the ignition and turn the key when doing so. Never force pushing the key into the ignition. 


Defective Key Tumbler/Ignition Lock Tumbler


While the SmartKey is standard on most Mercedes-Benz vehicles, some models, such as the ML Class, SLK Class, and Crossfire, used a metal blade key until 2005. It's likely that the key tumbler is faulty if you have a metal blade key instead of the Smart Key Remote. The key tumbler on some models is faulty. Even Mercedes with as little as 20,000 miles already have defective key tumblers. 


When checking the key tumbler be sure that the steering wheel is not locked. Then, without putting too much pressure on the key, push it into the ignition and gently jiggle it. It will become increasingly difficult to switch the ignition of your car as the lock pins on the tumbler wear out.


The ignition lock tumbler, also known as the “ignition lock cylinder,” is an essential part of your vehicle's starting system. When the ignition lock tumbler is successfully initiated, ignition will occur in the engine, allowing you to drive the car. It is made up of the tumbler and key assembly.  You also use an ignition lock tumbler to start the car's accessory systems, such as the radio. Since it's involved in so many different ignition procedures, it can show a wide variety of signs and symptoms that it's about to fail.


One of the most common symptoms of course is when the car refuses to start. Since the ignition lock tumbler is in charge of the initial ignition that starts your car, if it fails, your engine would as well. But if your vehicle still starts with several tries, then take it as a signal of an ignition lock tumbler that will be requiring servicing very soon.


Another common sign of a failing ignition lock tumbler is difficulty in inserting and removing key or commonly called “sticky keys.” If this is happening to you, first and foremost, double-check your key. Is there some kind of damage or warping that may be causing the problem? If this is the case, replace your key as soon as possible to maintain the condition of your ignition key tumbler, as a warped key may cause the cylinder to misalign.serve the condition of your ignition key tumbler, as a warped key could misalign the cylinder.


If your key is spotless, it's likely that tiny metal particles from repetitive key insertion over time have damaged your ignition key tumbler. If this appears to be the case, you can have your ignition key tumbler serviced by a licensed mechanic.


It's safer to leave the maintenance or replacement of your ignition lock tumbler to a technician unless you have prior experience in automotive repair. Every part of your car that is related to the functionality of your engine is better done by a professional for the same reasons as blindly delving beneath the hood. After all, you don't want to turn an easy, inexpensive repair into an expensive one.


Electronic Ignition/Switch System EIS/N73 Defect


A EIS module that has become defective could also be a reason for a “Mercedes turn key nothing happens” situation. Many car owners complain that their vehicle starts fine on mild or hot days, but not on cold days. This could seem unusual, but it is a common occurrence. Processors are soldered on the circuit board of the EIS, and in many cases, the processor's connections are poor or the processor itself is faulty.


If you are experiencing this problem, you will need to install a new / virgin EIS. Since the EIS must be coupled / married to the car using Mercedes-Benz Star Diagnostic Software, you cannot mount a used unit.


Smart Key Remote Issues


It's likely that the car won't start because of the key. The key will unlock the doors but not start the vehicle. The transponder coil wires can become detached and need to be resoldered in certain situations, or the key's processor may be faulty. In this case, the easiest solution is to order a new key from a Mercedes-Benz dealer.


How to order a replacement key from Mercedes Benz

  • Look for the closest Mercedes Benz dealer.
  • Secure your current vehicle registration or the original title if not registered.
  • Have your driver’s license or passport or other identity card ready.
  • Show the documents to the dealer. You will have to pay $200 to $300 for the new key. Or it might cost up to $560
  • You might have to wait 3 to 4 days for the new key to be shipped to the dealership. Some keys are made in the USA but in some cases they must be shipped from Germany, and you will have to wait up to ten days for them.
  • If you’re NOT the current owner of the car you will still need to secure all required docs as if you were the current owner in addition to a signed and dated authorization coming from the owner of the car.

Defective Electronic Control Module (ECU)


Another reason the car won't start is the Electronic Control Module (ECU). This issue would include the installation of a new ECU. Since the board is “married” to the car, you can't just swap in a used ECU and expect it to work. A second choice is to purchase a used ECU and move the processor from the old circuit board to the new ECU.


Discharged Battery/Undervoltage


Your Mercedes most likely has a battery problem if the engine cranks slowly but does not turn over. If your battery power is poor or the terminals are corroded, your power output suffers, and you'll have trouble starting your Mercedes.


It's likely that the car's battery is bad, as it doesn't have enough voltage for the ECU and the N73 Electronic Ignition/Starter Switch (EIS) to work properly. The CAN contact between the EIS and the N72 can not work properly if the battery is dead or has low voltage / under voltage.


The Mercedes-Benz EIS uses a coil to create a magnetic field on the Smartkey, causing the key to react to the car with a particular rolling code. Before you go any further, verify that you have a good battery with a $10 multimeter like this one.


Without the car running, the car battery can display at least 12.8 volts. The voltage should be about 14.4 volts when the engine is turned on. The ACDelco 94AGM Battery, which follows the OEM requirements, is a perfect option for most Mercedes-Benz cars that use Battery Group 94R.


Other Useful Tips


When you are faced with Mercedes turn key nothing happens situation you may try cleaning the EIS keyhole using a dry cloth. Careful not to use liquid to clean the EIS. Also look into the car’s fuses. Refrain from letting the vehicle’s battery from getting discharged while the key is in the ignition as this could damage the EIS or the key.

Mercedes Turn Key Nothing Happens: Other Frequently Asked Questions


What can cause No Crank No Start?


When the engine revs over and over without being able to control the vehicle, this is known as engine cranking. The word “crank” comes from the “crankshaft,” which is the part of your vehicle that drives the pistons. To power the car, the crankshaft and piston work together to transform the engine through its cycle and give the required spark to the cylinder to start the engine's internal combustion.


If you notice that your vehicle isn't cranking or starting, it may be due to a crankshaft or battery problem. The battery issue being the first thing you should check. 


Turning on your headlights is an easy way to diagnose and work out the battery issue. Assume the headlights turn on and remain at the appropriate brightness level, without flickering or becoming dim over time, then the battery function is correct in this case, and the battery connections are safe.


So if you are able to clear your batteries there are many other reasons why you have a no cranking/no starting situation in your car. You just have to learn how to diagnose this issue in your vehicle whether by using an inductance tester, carbon pile tester, and then check the battery connection.


How do you reset a Mercedes key?


You can do a reset of your Mercedes-Benz key by inserting it into the ignition when the car is switched off. Do not start the engine. When pressing the “click” button, remove the key from the ignition. Use another finger to repeatedly push the “unlock” button.


What does it mean when my car wont start but all the lights come on?


When your car won’t start but all the lights come on it may be caused by a battery loss, which occurs when something is left on and the battery drains. Weak connections, faulty battery terminals, or a bad or dead battery may all be to blame. It's likely that this is triggered by a corroded control terminal on the starter as well.


Aside from the breathtaking car designs and thrilling driving experience, many Mercedes drivers appreciate the quality engineering and long vehicle life Mercedes offers. But even with the most advanced technologies available in these German top-tier luxury vehicles, it can still begin to display the effects of time and use if not properly maintained.


When this happens, drivers also become panicked, frantically popping the hood and looking around, only to realize that the problem is unrelated to the engine. While this article has given you an idea of what is going on it's never a good idea to go into a vehicle's interior with an inexperienced hand. So, if you’re in a Mercedes turn key nothing happens, it's still best to seek professional assistance.