Weird start/non start issue security system? - PeachParts Mercedes-Benz Forum

jay_bob · #1 05-10-2022, 12:39 AM

The key towards your fingertips is the original key. Looks like for 99 they moved the panic button onto the business end of the key (my 98 had it in the butt end of the key).

The key in your palm is a later generation smart key. I can tell because the first generation keys that have the chrome sides, were built with a single membrane plastic piece (similar to your older key) for the lock, unlock, and trunk. The later version chrome keys have the buttons as discrete pieces of plastic that actually travel up and down.

When I ordered a replacement key for my 98 (in 2019) they sold me a key like that in your palm that worked intermittently. I also had the original black key for the car still and it worked fine. The person who sold me the car had gotten another key from the dealer in approximately 2011-2012 and it was the chrome with membrane style buttons and it worked fine. Unfortunately that 2011 era key got lost.

Now a little deep in the weeds theory on how these keys work. There are actually 3 things going on inside the key.

The first thing is the lock/unlock/trunk function, this uses radio waves to a receiver in the vehicle to handle the lock/unlock/pop the trunk functions via the PSE pump under the back seat. The W210 has pneumatic operated locks similar to the earlier generation vehicles dating back to the 1960s, they couldn't quite let that technology go even in the 1990s, after just about everyone else had been using solenoids by then and for quite a while before.

The second thing is an infrared emitter and receiver. This has 2 functions, first if you aim the remote at the receiver windows in the driver and passenger door handles, and hold down the unlock button, it will open all the windows and sunroof in addition to unlocking the car. Holding down the lock button closes all the windows and sunroof and locks the car. The receiver windows in the 210s have gotten roasted by UV from the sun by now and chances are this will only work if you are in the shade, have a fresh set of batteries in the key, and hold it directly over the door receiver window. The second thing the IR is used for is to help with authentication of the key. There is an IR transmitter/receiver also in the key slot in the ignition switch that also communicates with the key when it is inserted. I believe what happens here is this is re-synchronizing the rolling code for the lock/unlock function, since even in the 90s people were stealing cars by spoofing the remote unlock code.

The third thing the the key does is that there is a passive RFID chip in the nose of the key. I believe it is the same part as the grain of rice sized microchip they put in your dog or cat in case it gets lost. This is activated by a wire ring around the key slot, the code from the microchip is compared to the stored numbers in the security chip in the ignition switch, and only if they match will the drive authorization happy dance commence.

There is a whole chain of events that happens between key insertion and a successful start. Having access to Xentry is essential to see where things are breaking down. I see now you're in the STL area, don't know any forum members offhand who live near you with a Xentry unfortunately.

What happens if you use the original black key?

chaosrob · #2 05-10-2022, 06:47 PM

Thank you again.

It still does it intermittently, maybe I will try replacing the battery in that one as well.

It seems to work more frequently

Quote:

Originally Posted by jay_bob

The key towards your fingertips is the original key. Looks like for 99 they moved the panic button onto the business end of the key (my 98 had it in the butt end of the key).

The key in your palm is a later generation smart key. I can tell because the first generation keys that have the chrome sides, were built with a single membrane plastic piece (similar to your older key) for the lock, unlock, and trunk. The later version chrome keys have the buttons as discrete pieces of plastic that actually travel up and down.

When I ordered a replacement key for my 98 (in 2019) they sold me a key like that in your palm that worked intermittently. I also had the original black key for the car still and it worked fine. The person who sold me the car had gotten another key from the dealer in approximately 2011-2012 and it was the chrome with membrane style buttons and it worked fine. Unfortunately that 2011 era key got lost.

Now a little deep in the weeds theory on how these keys work. There are actually 3 things going on inside the key.

The first thing is the lock/unlock/trunk function, this uses radio waves to a receiver in the vehicle to handle the lock/unlock/pop the trunk functions via the PSE pump under the back seat. The W210 has pneumatic operated locks similar to the earlier generation vehicles dating back to the 1960s, they couldn't quite let that technology go even in the 1990s, after just about everyone else had been using solenoids by then and for quite a while before.

The second thing is an infrared emitter and receiver. This has 2 functions, first if you aim the remote at the receiver windows in the driver and passenger door handles, and hold down the unlock button, it will open all the windows and sunroof in addition to unlocking the car. Holding down the lock button closes all the windows and sunroof and locks the car. The receiver windows in the 210s have gotten roasted by UV from the sun by now and chances are this will only work if you are in the shade, have a fresh set of batteries in the key, and hold it directly over the door receiver window. The second thing the IR is used for is to help with authentication of the key. There is an IR transmitter/receiver also in the key slot in the ignition switch that also communicates with the key when it is inserted. I believe what happens here is this is re-synchronizing the rolling code for the lock/unlock function, since even in the 90s people were stealing cars by spoofing the remote unlock code.

The third thing the the key does is that there is a passive RFID chip in the nose of the key. I believe it is the same part as the grain of rice sized microchip they put in your dog or cat in case it gets lost. This is activated by a wire ring around the key slot, the code from the microchip is compared to the stored numbers in the security chip in the ignition switch, and only if they match will the drive authorization happy dance commence.

There is a whole chain of events that happens between key insertion and a successful start. Having access to Xentry is essential to see where things are breaking down. I see now you're in the STL area, don't know any forum members offhand who live near you with a Xentry unfortunately.

What happens if you use the original black key?