Mercedes Vito taxis, the workhorse of cities like Glasgow & Edinburgh, can experience intermittent issues with starting and stopping when the key is turned. This is often due to problems with the Electronic Ignition Switch (EIS) or related security modules. A failing EIS can lead to the ignition lights staying on even after the key is turned off, or the car refusing to start. Programming or repairing the EIS module is a common service we offer to resolve these issues.
What is an EIS (Electronic Ignition Switch):
An EIS is a module that’s responsible for verifying the key and starting the vehicle’s ignition process, as well as interacting with the steering lock and other security systems.
The Mercedes EIS has a switch that is like a small socket in the dash where the plastic key is inserted. The “key” has what looks like an infrared panel on the face of it, a bit like a TV remote control. the key contains a sequential code that is checked by the car with a series of handshakes to check that it is the correct key for the car.
Each time the key is inserted, the EIS system will “talk to the key” and check the key and then ask the ESL (Electronic Steering Lock) system for verification that it accepts that the correct key is being used.
The ESL system will then look to see if the Engine ECU (Electronic Control Unit) agrees that this is the correct key that is being used. It is only when all three systems are all happy that the correct key is being used, that it will the “Turn & Start” function to be activated.
Common Problems caused by a failing Electronic Ignition Switch:
Key not turning: Sometimes the key won’t turn in the ignition, indicating a problem with the EIS or steering lock.
No ignition response: Even if the key turns, the car might not start, or the ignition lights might not turn on.
Intermittent faults: The issue may appear and disappear randomly, making it difficult to diagnose.
Ignition lights staying on: After turning the key off, the ignition lights might remain lit, indicating a potential issue with the EIS.
Possible Causes:
Low key fob battery: A low battery in the key fob can interfere with the EIS’s ability to verify the key. We always recommend checking the battery first.
Damaged key: A physically damaged key can prevent the EIS from reading the security code. Check the key over first. Does it look damaged? We can supply & program new car keys.
Failing EIS: The EIS itself might be malfunctioning or failing to communicate properly with other modules.
Steering lock problems: The Electronic Steering Lock (ESL) module might be faulty and preventing the vehicle from starting.
Solutions:
Repair or replacement of EIS: In some cases, the EIS module can be repaired or replaced to restore functionality.
Key programming: The EIS module may need to be reprogrammed to recognise a new key or address a faulty security code. Contact KG KeyServices and
ESL module repair or replacement: A faulty ESL module can also cause ignition problems and may need to be repaired or replaced. we can help diagnose this for you.
