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MB Paul
MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4317
Experience:  Qualified Mercedes Benz Diagnostic Technician - 20+ years experience - Workshop Foreman for Mercedes
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Mercedes-Benz 180A how to bypass immobilizer in mers a140 my

Resolved Question:

how to bypass immobilizer in mers a140
my car batteries went low, when i tried to jump start, immobilizer blocked ignition
Submitted: 6 years ago.
Category: Mercedes
Expert:  MB Paul replied 6 years ago.

MB Paul :

Hi - sadly there is no way to bypass the immobilizer on the vehicle, the key needs to send the correct information to the drive authorisation system (DAS) module before the engine will start.

MB Paul :

Is the engine not cranking? Are you getting a "start error" on the dash?

MB Paul :

Do you have a spare key to try?

MB Paul :

Best regards, Paul

JACUSTOMER-bdzfr6ww- :

apparently there are car mecanics who are claiming that it can be bypassed i need to check car manual

JACUSTOMER-bdzfr6ww- :

i dont here any engine cranking

JACUSTOMER-bdzfr6ww- :

i have one electric key but i dont know where to insert it

MB Paul :

If you could bypass it then it wouldnt be worth installing on the vehicle! Unlike aftermarket immobilizers that are cut into existing wires on the vehicle, factory fit systems are fully integrated & send a data signal to the engine ECU to allow it to start, without the correct data signal there is no way to get the engine ECU to run the engine!

MB Paul :

The small black or red electronic key is a bypass for the alarm siren - this turns off the siren only. The receiver for this is usually in the glovebox - this was a dealer fit alarm system.

MB Paul :

The alarm has a couple of interfaces behind the dash - you could try removing these & plugging the existing wires back into the immobilizer system - the alarm connects to the cars own DAS system, these occasionally cause problems but usually with an immobilization issue on the A Class it is because the key has failed or more commonly the DAS module has failed.

MB Paul :

Just to confirm - you are getting a "start error" message on the dash indicating the immobilizer is blocking the system?

JACUSTOMER-bdzfr6ww- :

no i am not getting any start error message, so could it be somethingelse ?

MB Paul :

Hi - it could be just a fault with the starter motor which is far more common. Do you have access to a multimeter?

JACUSTOMER-bdzfr6ww- :

yes but not at the moment

MB Paul :

Ok - when you get the meter you can check for voltage at the connector to the starter located in the battery box. Inside here you should find a 3 pin connector block, one of the wires in this block is violet & white - this is the feed to your starter solenoid.

MB Paul :

Leave the connector plugged together & probe into the rear of the block with your meter set to volts, when you turn the key to start you should see around 12v here. If you do get 12v & the starter is not turning then it is likely that the starter is faulty. You shoul also check the main earth to the engine bolted at the bottom of the engine sump.

MB Paul :

If you do not get any voltage then disconnect the connector & probe into the wire on the body side (not the side that goes through the battery box - this goes to the starter) & turn the key to the start position again. If you now get battery voltage then the ECU is shutting down under load when the starter is connected. If there is no voltage still then the ECU is not putting out a signal at all or there is a wiring break (less likely option!)

MB Paul :

Let me know what you find & if you need anything else.

MB Paul :

Best regards, Paul

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