04 S55 IGNITION KEY WONT TURN
 

Been a while since Ive been here but Ive ran into an issue that has me stumped......my car (04 S55 W220) had been sitting for a while and my battery went completely dead (I suspected it was flaking out anyways) so I replaced it with a new one. Problem is the ignition key would insert but would not turn at all. I left it in the ignition overnight and still no luck. I have checked ALL my under hood fuses and the fuses on passenger side dash end and the fuses under the rear passenger seat. All are good. I moved the gear lever to neutral but still no turn of the key. I thought my EIS (ignition switch) was bad so I had another one cloned with my current switch information, installed it but no go. At this point I "think" Ive tried everything. I have 12v on both middle pins of the large plug on the ignition switch so the switch has voltage but it just wont turn. Does anyone have any ideas? Have I missed some fuse/s somewhere? Everything else works, lights, radio, fan, etc. Dash lights up with door open. Where should I look? My STAR system cant get codes unless the ignition is on an car started so thats no help. Ideas?
SOLVED......apparently my key and switch were fine AND were getting +12v to the switch BUT was not getting a signal from the front drivers side fusebox (broken cable perhaps) so I ran a cable from the OBD port and she started. All is now working fine.

Have you let the battery charge up all the modules overnight WITHOUT the key in the ignition? The only time I've seen this is when my battery died BECAUSE I left the key in overnight. But after I charged the battery again (key out of the car), it was fine. Leaving the key in the ignition keeps all "sleeping" modules "awake" and drawing power (my layman's explanation). Battery out gives the modules time to charge up, so they respond properly to recognizing the key. Do the lock and unlock, trunk open functions work YET with the new battery? Once those start working again, your key should work as well.

maw

Maw, I never actually left the key in when I charged the battery at first. I suspected the battery was going out so I just replaced it. I only left the key in the car for a few hours (with new battery) to see if the car "learned" the new key but no go. The door unlock/lock function does NOT work with old EIS or the new one. I'm kind of stuck with this one....the car was fine until the existing battery went completely dead. Now I have a brand new battery and nothing will do ****. All my fuses are good, full charge battery, etc. Ive been disconnecting the battery after trying the key until next time I screw with it. Should I just leave the battery connected and try it again next day? If it matters I bought an EIS coil "test" device, works on BMW, Mercedes, etc. I tried it on my BMW......it works by reading the coil voltage in the key when you insert it and an led comes on to let you know your key and switch are good. I tried it on the S55 and get nothing with both keys. Not sure what that means....Im stumped here...

Yes. Leave your new battery connected overnight and see what happens in the morning. That's what mine took. My only guess is there are some module(s) in the car that needs to be powered up in order to recognize the key, likely some combination of the EIS, SAM and DCM. I'd go with the original EIS, just to take the clone out of the picture. I'm not well versed on all the modules in these things (not a tech, just an owner). See here if you want to get into the weeds...https://w220.ee/WIS_54.21_Control_Units/Modules. Also here...https://w220.ee/Battery. Note they say "many ECUs" malfunction on weak batteries -- no clue of which ones, what the malfunctions may be, charging level, nothing. But I've observed that all sorts of things go bad when these cars' batteries are weak or dead (notice the hulking sizes of the batteries), everything from bad shifting to keys to windows. Letting all of the modules recharge to a certain level I've found helps matters. Like you, I leave cars sit for months at a time. For example, window controls (auto up, auto down) take a while to come back online for Audi and BMW after changing or charging batteries. Never understood why, but it's true. If you have a Schumaker around (I suspect you do), I'd put the new battery in AND hook it up, so the new battery has a source while it recharges the modules. That's probably overkill, but you see where I'm headed. Eventually I had pig tail tricklers installed on all my cars so they just plug into the wall while they sit.

GL, please report back.

maw

It DOES get frustrating and what youre saying sounds like common sense. Ill try the full charged NEW battery hooked up overnight WITH the trickle charger.......sounds like solid advice. I'll let you know. Thanks for chiming in.

Make sure the charger is set to slow charge, something below 15A, so it doesn't burn out the modules. Mine is adjustable and has a 2A slow charge that takes overnight sometimes but won't hurt anything (auto shutoff). I don't use it much now that I've put the pig tails on -- it's just easier to not let the batteries drain in the first place, as you see.

GL

maw

Maw............tried your method over the weekend and nothing....still the same. Left it on trickle charge (battery connected to car) overnight and tried key the next day.....same crap. Key goes in but wont turn. Where do I go from here?

This is the cloned EIS module......no, the key wont do anything (locks/alarm/etc and never did even before I cloned the EIS......to clarify...the key will NOT perform any remote function...

Fob battery is brand new.......as is the one in the car.

All this **** started when the car sat for a month and the battery went completely flat......maybe I do have a dead module but which one...

Is you get some time, try disconnecting the cpu in the passenger side fusbox. Its the main ecu for the car. Unplug all the wires and plug them back in. Sometimes they jist need a wake up afyer sittong for so long. That ecu works in correspondemce with your key.

Thanks Sike.......will try that.

SOLVED.......see above.

Will try that as well, with fingers crossed.