Barchae

Dear fellow mercedes drivers,

I hope you can help me out of a predicament here, let me explain what happened and hopefully we can resolve this.

Driving home from work, nothing out of the usual happened, i park my car, exit and want to lock it using the remote key. This key can sometimes be a bit tricky, 1 times out of 10 it doesn't register the first time, so I have to press a few times before it locks up.
Thought the battery might on its way out. Anyway, this time, pressed 3 times, but didn't lock, didn't matter I thought, its in my drive and went inside. The following morning i tried to "unlock" the already unlocked car, so the alarm doesn't sound. Again, no response, at this time i didn't check the light on the remote key, but the batteries may have been dead. So i opened the door, facing the blaring alarm and inserted the key into the ignition to silence it. Nothing, the alarm kept on going, and I could not even turn the key in the ignition to any other point.

Got out of the car, the alarm stopped after about 2 minutes but the turning signals kept on blinking for another 30 minutes or so.

Went to the store to get new batteries for the remote key, red light blinks on again when i press buttons. Tried it near the car, nothing.

What i have checked so far, i opened up the key, no loose soldering of any kind. Checked the infrared light.
The re-sync method of holding down the lock key, pressing unlock 5 times then boot key.
Checked all fuses under the hood and under the rear seat.
Disconnected the car battery (the grounding wire) -> this causes a strange effect, i thought the alarm would sound, but its making a weird chirping noise instead.
Reconnected after 15-20 minutes, no change.
Battery is still ok.

Its a w210 elegance from 1999, pre-facelift e200 cdi.
The key has 3 buttons, no panic button and is completely black. I have never seen any red/green leds on the doorhandles or mirror. (might've been a red led in the mirror, but i just never took notice)

I only have the one key, no spare.

I really hope you guys can help me out in any way.

Thanks for your time,

Sincerely,

Steven.

raymond g-

questions:

PSE pump - any signs of water damage or moisture anywhere? should be ZERO

you say car battery is ok but that does little to describe the condition. so more details on how you tested this would be good

Smartkey: you say no loose soldering of any kind but do not describe how you confirmed this is accurate. did you try cleaning the circuit board yet? did you try cleaning the IR window of the key? did you check the IR light which should pulse with each key button pressing?

when you inserted the Smartkey into the ignition what sounds do you hear?

you say you checked all the fuses under the hood and under the seat but did not describe if this was simply a visual check or if you used a continuity tester et al. by the way, there is still one more fuse panel at the end of the dash but that should contain mostly circuitry related to lighting

if you disconnected the car battery, there should be no power. but you continue by saying that with no power, the siren (under the fender) begins chirping. is this accurate? how long did it continue even without a power source?

Barchae

Thanks for the reply,

Sorry if I did not elaborate too much, i didn't want the post to become too long.
No water damage anywhere around the pump it looks brand new, its insulated in a foamlike material.

The battery actually is new and I tested it with my multimeter. Also the battery has a window on it to show its status, it says fully charged. Also the headlights show no sign of dimming.

I disassembled the entire key and checked. It looks perfect, no corrosion either.

When inserting into the ignition, nothing happens. No click or any sound of any kind that it usually makes when it does the handshake thing.

The fuses were also all checked with a multimeter, so i'm sure they're fine. Indeed also checked the ones on the dash on drivers side, only a visual check on that one because as you stated, those are for lighting mostly.

I disconnected the battery, but to my knowledge, there is a seperate battery inside the siren/alarm. So I thought it would keep on sounding, instead i got this chirp sound, not very loud. It lasted a good 4-6 hours or so before it stopped.

When i reconnected the battery after 8 hours or so, the alarm came on immediately and the key did nothing still.

I hope this helps clear things up.

raymond g-

thanks for the background. i'm just jumping into the mud puddle with you as I'm far from an
expert.

i would feel better if it could be verified that the car battery was in good health while under load.
a local auto parts store frequently provides this service for free if you bring the battery in. so
with respect to the little clear lens in the battery (flooded wet cell, not AGM) I've seen where it may
glow but the overall battery was subpar. so think about that clear lens giving you a peek into a
single cell and identifies the electrolyte condition....though with a little tunnel vision though. it
is still useful but on rare occasion, can be misleading. load test is much more definitive an
indicator.

the fact that the ignition doesn't click and whirl when the Smartkey is inserted causes me to think
1) the car battery is too low, 2) the handshaking / interrogation is not occurring and which is needed
to even begin to start the car.

you mention that the headlights doesn't appear to be severely dimmed. this isn't a good test though
it would be a good indicator if you had the headlights on AND were able to have the engine cranking.
but this isn't the case which is why battery load testing is still needed. the headlight, cabin lights,
radio, blinkers, etc are not good indicators whether the car battery is healthy enough to power the
EIS and starter which require a higher voltage/amperage.

if it was my vehicle exhibiting the symptoms you've described, I would first get the car battery tested
under a heavy load. once that has been verified in good health, I'd then insert the Smartkey into
the ignition and leave it there and have lunch. this is what might be referred to as synchronizing
the Smartkey to the EIS that the dealers charge people $50 for (smile).

I'll stop here. The troubleshooting is a bit of a dynamic flow chart and the above can be viewed as
issues upstream which need to be answered first, i.e. before tackling the door locks which may be
RF related, or PSE related.

I'm sure others may jump in who may have more experience

raymond g-

p.s. I didn't know that the siren had an internal battery(ies) so you may have helped ME out here. I have
a siren on the project bench which I will now try to dissect as it isn't operating as a PnP replacement.

raymond g-

another thought: if the siren is integral with the security system AND the chirping is an indication of it
failing, might this impact the car's ability to start the car (door locks, etc) until the siren is replaced ?
hmm...will need to dig into that a little more

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That is what I was thinking as well.

I will try leaving the key in for a couple of hours though, but I do not believe it will help as I have read that the red light on the key has to come on for this to work, which it doesn't.

Don't have a dealer nearby to put a load on the battery, but a bad battery seems really unlikely. What I can do is completely charge it again at the wall and/or "jumpstart" with another car. Will try both today.

Thanks for jumping in this puddle with me

bbirdwell

I'm leaning towards a bad electronic ignition lock and a trip to the dealer for service; testing requires dealer-grade maintenance gear. The parts are considered theft-relevant and can only be ordered by the dealer and must be enabled by the dealer using the workshop key.

IIRC, the EZS (authorization module) is located in the EIS (electronic ignition switch) but please don't hold me to this as I have never disassembled one to find out. Once the EZS confirms the key fob has a valid code, it releases the ELV (steering lock) and signals the ME (motor electronics) all is good.

If the key fob fails to unlock via both Infra-red and radio frequency, that points towards a bad drive authorization module or a failed key fob. Infra-red works through the door control module and then to the CAN C bus; the radio frequency works through an antenna receiver located (somewhere) on the CAN C bus. In both cases, the code is transmitted to the EZS.

Not much help for you but let us know what you find.

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Hi bbirdwell,

My key is not exactly the same (no panic button) but this probably won't make a difference.
Thanks for the flowcharts, it indeed looks to be pointing towards an ezs problem.
Don't know if it is then worth it to tow the car to the dealer and then parting with lots of money to fix this as I assume this won't be cheap.
Car ran fine for two years and was maintained well but only costed me 2.000. So this is probably not worth it.

Also an update to let you know that "jumpstarting" and leaving the key in for a couple of hours did not help unfortunately.

When I have time, i'll try to see if I can locate the siren (which is behind the wheel well) and replace the battery there. If it still doesn't work, probably head over to checking if there isn't any loose wiring in the car that's connected to the security system.

If anyone thinks of anything else, please let me know!

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Contacted specialist from a mercedes garage and got told that a dead siren battery could not cause these issues and that it most likely is as we thought, a bad EZS.

Sadly this is too costly for the car and I'll let it go.

Thanks guys for your insight and help!

Steven.