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MB Paul
MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4317
Experience:  Mercedes Benz Qualified Diagnostic Technician
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1998 e300 diesel automatic estate. sometimes key wont turn

Customer Question

1998 e300 diesel automatic estate. sometimes key wont turn to unlock steering and cancel immobiliser, if left unlocked key will turn but not turn over, obviously for security reasons. have to keep inserting key, turning wheel until it acknowledges key and will start. Have tried new batteries in key. is it some expensive electronic unit needs replacing?

Still waiting!

Submitted: 3 years ago.
Category: Mercedes
Expert:  Shantal-Mod replied 3 years ago.

I'm Shantal and I'm a moderator for this topic.

I've been working hard to find a Professional to assist you with your question, but sometimes finding the right Professional can take a little longer than expected.

I was checking to see if you had already found your answer or if you still need assistance from one of the Professionals.

Please let me know if you wish to continue waiting or if you would like for us to close your question?

Thank you,

Expert:  MB Paul replied 3 years ago.


Sorry you have had a wait & I hope I can still assist you with your problem.

There are several points of failure on the car for this problem - the key sends a signal to the EIS (electronic ignition switch), if the EIS detects the correct key then it sends a signal to the ESL (electronic steering lock) to unlock the steering, once unlocked it sends a signal back to the EIS to allow the key to turn & the engine to start.

So in theory it could be the key, the EIS or the ESL.

Key failure is a common problem & it is wise to get a replacement key to rule out any key problems - batteries are only needed for the remote central locking & not needed once the key is inserted in the ignition to turn the key, so batteries would not be an issue.

The main vehicle battery should also be checked to ensure it is in good order.

If the car still has this problem with a new key then diagnosis on Mercedes STAR diagnostic tool is required to see what signals are being sent & if any codes are stored.

The key is the most common failure, followed by the EIS & the ESL being the least problematic of them all.

Both the EIS & ESL need coding on STAR after installation before they will work.

Best regards, Paul

Customer: replied 3 years ago.

this is not much more than I have already been told by my garage mechanic and has taken FIVE days?!! Can't say that I'm very pleased at all.

Customer: replied 3 years ago.
Relist: Answer came too late.
refund my fee
Customer: replied 3 years ago.

just refund me