Guides on how to fix and diagnose EIS (Electronic Ignition Switch) Failure on a Mercedes-Benz.
Table of Contents
Signs or symptoms of having a faulty EIS (Electronic Ignition Switch) Failure
Cannot turn the key when inserted on the EIS
The vehicle won't start when twisting the key
Can turn the key, but the car won't start.
Cannot start the vehicle when it's cold
Reasons why the EIS (Electronic Ignition Switch) is not working
Low battery voltage output
The voltage output on the wires to the device are high
The key is in the ignition while connecting the jumper cables
Solutions on how to fix the EIS (Electronic Ignition Switch)
Insert a spare key into the EIS and try switching the vehicle on. If it works, then the problem is probably the vehicle's key. To make sure, use the spare key for a few days to confirm that the problem is with the key and not the EIS.
Scan the vehicle using a Start Diagnostic Scanner to check for fault codes. This procedure will work if the ignition works.
Connect a multimeter on the starter on the SAM (Signal Acquisition Module), set the multimeter to DC voltage, and then insert the key on the EIS and turn the key. If there's no voltage output, then there's a problem with the module.
Replace the EIS; this solution will need to change the VIN (Vehicle Identification Number) of the EIS to match it with the VIN of the vehicle.
Remove the EIS on your vehicle and send it to a shop where they can diagnose the problem and fix the EIS problem.
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