Mercedes Benz EZS Fault

A Common issue for many models across the Mercedes Benz range is a faulty EZS. This is basically the vehicles imobaliser system, ignition switch and control module all in one.

This fault can be caused either by a defective key, bad shifter module, a failed Electronic Ignition Switch EZS. 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:

  • Key does not turn in the ignition due to failed EIS
  • Key doesn’t turn during cold weather
  • Key may turn, but the instrument cluster lights don’t turn on
  • Unable To Turn The Key, Unable To Start The Car
  • Can turn the key but car won’t start
  • Mercedes key intermittently works
  • Push start button no longer works

Common causes

Mercedes-Benz ignition switch (often referred as 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
  • Connecting jump starting cables while key is in the ignition.

Before condemning the EZS make sure the fault is not with the key itself. Try starting the vehicle with you second key. if it now works you have a faulty key. Unfortunately ninety percent of the time the fault is not with the key but with the EZS module.

The remedy requires either the module to be repaired or replaced. If you are unfortunately enough to have a four wheel drive vehicle you will have the added problem of your vehicle is now locked in park, making towing it a vey difficult task. It can be done with a tow truck fitted with a cradle.

The ignition switch needs to be removed and either repaired. some independent repairers can fix them, or simply replace the EZS. This requires the module to be coded to the vehicle and the keys nodded to the new module. You can’t simply buy a second hand EZS plug it in and away you go.

We have done this repair a few times on a variety of Mercedes Benz vehicles. Prices fluctuate depending on the model but repair costs start at $1700 and only go up from there.
If you suspect you have this fault give us a call and we can help you repair this. 

1 thought on “Mercedes Benz EZS Fault”

  1. Juraimi Abdillah

    Usually when I turn the key at ON MODE, I can hear the sound of fuèl pump ànd then only we can start the engine but now is different thing happening … when I turn the key to ON MODE there is no sound of fuel pump bit when I start to crank … only then the sound of the fuel pump starts coming .. its the opposite … then my mechanic said the EIS is faulty

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