A problem that Mercedes-Benz owners may face is the key no longer turns in the ignition. This issue is often caused by a defective key, a bad shifter module, a failed Electronic Ignition Switch (EIS), the EIS-EZS, or a bad steering lock module (ESL). This problem can affect various Mercedes-Benz models, including E-Class, S-Class, C-Class, CLK-Class, ML-Class, SL-Class, etc.
Possible Symptoms
Possible symptoms of a failed Mercedes-Benz include:
- The key does not turn in the ignition due to failed EIS
- The key doesn’t turn during cold weather
- The key may turn, but the instrument cluster lights don’t turn on
- Unable To Turn The Key,Unable To Start The Car
- I can turn the key, but the car won’t start
- Mercedes key intermittent works
- The push start button no longer works
Common causes
Mercedes-Benz ignition switch (often called immobilizer module) can become faulty and, in some cases, due to user error. For example, some common reasons why the ignition module failed are:
- Low battery voltage
- Power surge due
- Connecting jump-starting cables while the key is in the ignition.
During any of the above scenarios, the EIS-EZS may lose its memory. While it can be diagnosed with Start Diagnostic Scanner used at dealerships, it can’t be repaired with this scanner. Mercedes dealers don’t repairer a bad EIS-EZS module. They will recommend that the module be replaced. That’s not necessarily the only solution; see alternatives below.
How to fix Mercedes Ignition Switch Problems
Step 1
A defective key can very well cause these symptoms. If you have a spare key, try to see if you are experiencing the same symptoms with the other key. If the other key works, keep using it for a couple of weeks to verify that the issue is the key and not the EIS.
Step 2
Try scanning your Mercedes-Benz for fault codes. Ideally, use a Start Diagnostic Scanner. This scanner should still retrieve fault codes when the ignition is off. If you don’t have this scanner or know of a shop that does, a possible alternative would be to use a YOUCANIC scanner. The only issue here is that if you can’t turn on the ignition, you can’t power on the OBD2 port and the scanner. If the ignition turns intermittently, consider yourself lucky and scan for codes. Hopefully, there are fault codes that will point you to the problem. 
Step 3
Diagnosing Mercedes ignition problems isn’t a simple DIY job. You may consider taking your car to the dealer or an independent shop and having them troubleshoot the problem. If they conclude that the Ignition Switch (EIS-EZS) is the culprit, you will be told that the switch must be replaced. This is an expensive repair that can cost several hundred dollars. You have a few options here. Have the dealer install a new ignition switch, and they will program it to match the VIN of your Mercedes-Benz. Many owners install an ignition switch, ECU, shifter module, and other parts from a donor vehicle. You can’t replace the ignitionswitchonly with one from a used Mercedes-Benz. Several parts must be swapped because the stored VIN needs to be the same.
There is also a third option, which may be the cheapest way to fix the Mercedes ignition switch module. Some companies can repair Mercedes-Benz ignition modules. You will need to remove the ignition module from your Mercedes-Benz and ship it to one of these companies that can test and repair the EIS-EZS. Once the module is repaired, it is returned to you. Besides being a lot cheaper than installing a new ignition module, it also doesn’t require any programming or coding. The VIN stored in the Ignition Module (EIS-EZS) matches that of the car; it’s your old module, after all. Just install it, and you are ready to go.
Where to find Mercedes Ignition module repair service:
Check out these companies that provide the Mercedes EZS EIS Ignition Module online.
- MERCEDES BENZ EZS EIS IGNITION REPAIR SERVICE
- Several businesses in US and Canada offer EIS, EZS, ESL, KEY, electronic ignition switch, and electric steering lock repair services for models such as:
- W202W203W208W209W210 W211 W220 W215 W219 W230 W463 W639W906
- Mercedes-Benz A B C E G S SL ML GL SLK Class
- Several businesses in US and Canada offer EIS, EZS, ESL, KEY, electronic ignition switch, and electric steering lock repair services for models such as:
What is the Best Scanner to Use for Diagnosing Mercedes-Benz Vehicles?
The YOUCANIC full system diagnostic scanner is a powerful tool to help you troubleshoot Mercedes-Benz problems quickly and efficiently. This scanner can communicate with all the control units in your Mercedes-Benz, including the engine, transmission, ABS, SRS, and more. By accessing real-time data from these control units, you can pinpoint the root cause of the problem and take appropriate action to resolve it.
Whether you’re experiencing issues with your engine, transmission, or other systems in your Mercedes-Benz, the YOUCANIC diagnostic scanner can provide valuable insight into what’s going on under the hood. This scanner can help you identify error codes, read live data, and perform special functions like reset adaptations or component tests. With this information, you can make informed decisions about repairs, maintenance, and upgrades to keep your Mercedes-Benz running smoothly.
Overall, the YOUCANIC full system diagnostic scanner is invaluable for any Mercedes-Benz owner or technician looking to troubleshoot problems quickly and accurately. With its user-friendly interface and powerful diagnostic capabilities, you can save time, money, and frustration by diagnosing and resolving issues with your Mercedes-Benz quickly and efficiently.
