My Mercedes has an intermittent no-crank condition. When I put the key in and turn it to position 2, the dashboard lights come on normally, and I can hear the steering column lock release. However, when I turn the key to the START position, the starter does not engage. There is no obvious clicking from the starter.One unusual thing is that disconnecting and reconnecting the battery once allowed the vehicle to start and run normally. I was able to shut it off and restart it several times. However, after turning the vehicle off, closing the door, and returning to it, the no-crank problem came back. Repeating the battery reset has not consistently fixed it.
Other electrical symptoms:
Central locking does not work.
Both front power seats are inoperative.
The steering column lock releases normally when the key is inserted.
The key's remote LED works, and remote window convenience functions work.
I have only one key.
I inspected and cleaned several chassis and engine grounds and installed two additional braided ground straps between the transmission and chassis.
I inspected the starter's main power connection and measured approximately 12.9 volts with the key off.
I have been investigating the starter solenoid trigger signal, but I have not conclusively identified every starter terminal.
I also found a seat adjustment relay with a discolored/burnt-looking pin.
My questions:
Does this sound like a faulty Electronic Ignition Switch (EIS), immobilizer/DAS authorization problem, engine computer, or wiring/power supply issue?
What tests should I perform to determine whether the EIS is recognizing the key and sending the start authorization signal?
Could a faulty ground, fuse box, relay, or door electrical module cause these symptoms?
What diagnostic readings should I check before purchasing replacement parts?
Other electrical symptoms:
Central locking does not work.
Both front power seats are inoperative.
The steering column lock releases normally when the key is inserted.
The key's remote LED works, and remote window convenience functions work.
I have only one key.
I inspected and cleaned several chassis and engine grounds and installed two additional braided ground straps between the transmission and chassis.
I inspected the starter's main power connection and measured approximately 12.9 volts with the key off.
I have been investigating the starter solenoid trigger signal, but I have not conclusively identified every starter terminal.
I also found a seat adjustment relay with a discolored/burnt-looking pin.
My questions:
Does this sound like a faulty Electronic Ignition Switch (EIS), immobilizer/DAS authorization problem, engine computer, or wiring/power supply issue?
What tests should I perform to determine whether the EIS is recognizing the key and sending the start authorization signal?
Could a faulty ground, fuse box, relay, or door electrical module cause these symptoms?
What diagnostic readings should I check before purchasing replacement parts?
Nov 3, 2026 at 4:26 PM
