The Mercedes-Benz keys for the W140, R129, W163, and early W210 generally come in the form of a switchblade remote style. Keys were also made that did not include the remote functionality and others that had limited key functionality known as valet keys that would not unlock the glovebox or trunk.
The keys for these models use two layers of security to start the engine. The first layer is the physical key itself, a metal blade component which moves pins in a physical lock and allows the ignition switch to rotate. There is a second component inside the key, a transponder or immobilizer chip that functions in combination with an antenna/activation ring that surrounds the ignition switch. When one turns the key to the start position the ring around the ignition switch energizes the chip inside the key, if the frequency and code emitted from the immobilizer chip in the key matches what the car expects it to be the AAM (All Activity Module) is authorized to enable fuel and spark to start the engine. Without authorization only the starter will spin and the engine won’t stay running or start at all, depending on the model, Start Error will be displayed on the odometer screen.
Mercedes is the only one that can supply replacement keys with immobilizer chips. Since late August 2017 Mercedes has been unable to supply replacement keys with immobilizer chips.
This means if you have one of these affected models and your key is lost or damaged it’s game over. The car becomes an expensive and oversized paperweight.
Mercedes Magazine followed up on the service bulletin released in 2017 by MBUSA. Two large Chicago area Mercedes dealerships confirmed they could not obtain a replacement key for the Mercedes Magazine 1998 CL600 C140 coupe, one of the affected models. The Mercedes-Benz Customer Support Line at MBUSA also confirmed they could not supply a key. We also contacted the Mercedes-Benz Classic Center in Irvine, California who now are tasked with supporting most of the models that use this style of key and they too are unable to supply keys for these models.
What’s the solution?
While the immobilizer chip part of the keys are not available, key blanks are. The biggest concern comes if the keys immobilizer chip is damaged or lost since a replacement blade could be easily acquired and cut by locksmiths. The best solution we can provide is to suggest disassembling a working remote control blade key. Inside you will find the remote control circuit board that controls the remote lock/unlock/trunk release functions. Separate from this in the corner of the plastic housing you will find a small black transponder chip. Remove this chip from the remote key and reassemble the key. Take the small transponder chip and attach it to the inside of your dash with tape or another adhesive. Get it as close as possible to the ignition switch, it needs to be within a few inches of it. By doing this the chip will always be with the car so if the key is lost of damaged you don’t need to worry about not being able to acquire a replacement chip all you need to worry about is acquiring the easy to source metal blade key blank and have it cut to your ignition.
Mercedes Magazine will continue to follow up with MBUSA and will update this story if these keys become available again.