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A tale of two keys

When investigating the cause of a reported non-start on a Mercedes C-Class, Ross Kemp of Scantec Automotive discovers that the key to solving the issue was in fact…the key.

We were recently tasked with investigating a Mercedes C-Class after the customer reported symptoms of a non-start. The owner of the vehicle was able to insert and turn the key in the ignition switch, but with no ignition being activated.

On arrival, we immediately realised that only one key was available for the vehicle – somewhat of a hindrance in these cases as the official test method for these symptoms relies on having two keys available. Having experienced these types of symptoms many times before, we were happy that we had the required knowledge, training and experience to accurately diagnose the issue, so we proceeded.

Step one

Our first step was to support the battery and carry out a global fault scan analysis using the Mercedes diagnostic platform. As expected, we had several modules on the network not responding, due to the fact that we were currently unable to activate the ignition. This was a symptom of the underlying fault(s) and not currently considered relevant.

As the electronic ignition switch (EZS) is responsible for activation of initial ignition power supplies and other vehicle wake up commands, we concentrated our initial investigation here. The first positive observation was that the EZS module was responding to the diagnostics tool, and we were able to gain comms with the unit for further diagnosis. Typically, this suggests that the main power and ground supplies to the EZS are, in fact, present and correct.

After analysis, we noted that no faults had been stored and/or presently reported by the EZS module, so a quick data check within the EZS confirmed that the module did indeed have a good power supply, that it was correctly programmed, and that no keys had been disabled, etc. However, data analysis did confirm that a key was inserted, but it was being reported as ‘Not Valid’.

After a few other basic checks, we were happy to advise our customer that a new key should be sourced. As a genuine key does not require programming and as this was a mobile booking, we simply advised that our customer should take the relevant documents to the local dealer and source a new key.

Never that easy

We were somewhat surprised to receive a phone call from the customer a few days later informing us that the new key had not improved the situation. After rechecking our vehicle logs, job card and test results, we were still 100% sure that the original faults presented to us were that of a defective key. But, had something else been missed? Was there more than one issue here?

After carrying out further checks, we discovered that the VIN number on our diagnostic report did not match up with the VIN reported by DVLA. It transpired that at some point in the vehicle’s life and unbeknown to the current owner, the vehicle had had a replacement of the engine control module, ignition switch, steering lock and key, all from another vehicle. This effectively gave the vehicle two completely different identities!

The owner quite rightly ordered a new key for their vehicle based off of the required V5 document, only to find that this key was never going to be accepted by the vehicle. So, the owner could not get a new key, as you are unable to order a key to VIN without a V5.

Questions to consider

For us, we now have a new procedure in place to check the V5 against the vehicle’s displayed VIN and cross-check against the VINs programmed to any and all relevant control modules.

However, we must wonder why someone felt the need to splatter the vehicle with second-hand parts in the first place and why the owner was not aware of this situation.

The chances are that one of the replaced parts had failed, as they clearly can’t all have failed at the same time. Was the technician unable to diagnose the issue correctly, and so changed everything? Were they unable to program the original, failed part? Were they trying to save the owner money? Did they inform the customer of the ramifications of this type of repair, or did they even grasp the possible ramifications for themselves? Did they even inform the customer?

We tend to be seeing similar issues to this on an ever-increasing basis. At Scantec, we do not condone this type of work, or similarly programming non-genuine keys by means of vehicle hacking!

Why? Because, as diagnostic specialists, we have seen multiple jobs that end up costing the owners 10 times more than what it should have cost had the repair been carried out correctly and professionally in the first place. Normally, it all goes undetected until someone comes along and tries to carry out what would have been a simple process. Except now the process takes far longer than it should do because the professional has to unpick what went before.

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