1999 E300 Key would not turn...then it did
 

I'm in the process of reading various threads on this and other forums...but thought I'd lay down specifics and see if anyone has any insights.

Son drives 99 E300 with 160k miles. Started the car to move it to a different spot in the driveway. Five minutes later, having shut the car off, he inserted the key (electronic, not mechanical) and nothing....no "click" and it wouldn't turn. So he tried and tried and tried and tried....nothing.

Then, after trying a while, he stuck the key in and heard the click but it still wouldn't turn. I was with him on the phone and asked if there were any signs of battery weakness. All lights, including headlights, seemed fine.

So then, just for the heck of it, I had him disconnect and reconnect the battery. Still nothing. I had him remove the batteries from the key fob just for the heck of it.

Then, after an hour or so, he tried again and it turned. But he had forgotten to glow....so he turned it off, turned and glowed and it started right up.

Initially there were ESP and ABS warnings on but he could clear those out.

I'm assuming I'll just need to take it to my mechanic. But if anyone has any diagnostic suggestions, I'm all ears. I wonder if K40 relay is likely culprit.

Thanks.

On my 98 E300 I have a fairly new key that on occasion won't turn when key is inserted. Pretty random issue that I have not looked into yet.

Sounds like the steering assembly is applying pressure that keeps the key FOB from being able to be turned to me. Prevalent in the W210 and W211 I've owned. Relieve the pressure by turning against the pressure side on the steering wheel, that happened when shutting the engine down, and then turn the FOB.

Although initially it wouldn't even make the click sound… That would not be due to pressure, would it?

It hadn't occurred to me that perhaps the key itself could be the problem.

The W210 electronic steering lock, for the uninitated, uses the "smart key". There are 3 components to the system:
- an RF-based system that transmits the unlock/lock/trunk/panic commands to the car. This is how the car locks and unlocks.
- and IR based system that transmits the above commands to the car. This is used for the "convenience" features, like opening all the windows if you hold down the "unlock" button.
These 2 features use the 2 CR2025 lithium batteries inside the key.

The third element is the DAS authorization chip. This is what unlocks the steering (and also lets the rest of the car function). It is an RFID chip that is inductively powered from the transmitter in the key switch. It has nothing to do with the lithium batteries in the key. I believe this is actually the same device that they use to "microchip" your dog or cat. Not 100% sure on MB but I know for a fact that is what Honda uses for the "immobilizer" system.

When you insert the key, the DAS system queries the RFID chip, and if the DAS accepts the stored serial number in that key's chip, then it allows the steering wheel to unlock (the 'zzzt' sound). From my experience, this locking system does not seem to have the same problem as mechanical steering locks, that can get bound up if the wheel is turned off center or something is putting pressure on the lock.

This locking mechanism apparently consumes energy, because if you put the key in the lock, but don't start the car, it will eventually time out and re-lock the steering wheel. In order to unlock the wheel, you have to take the key out and reinsert it. This is mentioned in the owner's manual.

One other thing the manual cautions about (and my Honda's manual says the same thing) is to not have multiple RFID keys for different cars on the same ring. I have personal experience with this, since I am fortunate enough to have 2 late model MBs with the Smartkeys. I have never had a problem with the 2 keys interfering with each other, either with the MB system, or the Honda system (when I had 2 Hondas) or if you have an MB and Honda key on the same ring. Only problem I have is if I put the wrong MB key in the car. The 210 just sits there and won't unlock. The 164 puts a message on the console that this is not the correct key.

All that said, I would be looking at my K40, but as TJTS1 says, just reflow the joints.

how cold was the ambient temperature when this happened? I read on another forum about heating the EIS shortly with a hair dryer and everythign started working again.

This fault is the beginning of EIS trouble.

you explained it perfectly on how this key system works, two sets of codes are interrogated from the key, one to release the steering from arrest position and the other to release the car for starting.

I also saw a few videos of some european key makers and tools who test and rework the EIS and also the ESL. Its pretty nifty even today, They use an illuminating ring to test the inductive charging system for the key and have a special key that can read the EIS too.

Very informative overview, Jay Bob....thanks.

It was about 25F outside when it didn't work. What/where is EIS?

I think I'll test the battery just to confirm it's solid and then resolder the K40 and see where I stand.

The EIS is the electronic ignition switch, the little hole you stick the smart key into.

In colder weather it has been known to go a bit cuckoo - some have fixed it temporarily with a hair dryer for a few seconds. I have a habit of inserting key and waiting for the lock to "bzzt" then turn the key on each detent rather than simply jamming and twisting the key.

In my driving years I have done this on all sorts of cars and it worked everytime.

it also is wise to only have the smart key and a little key ring, do not dangle a bunch of keys on the same key ring, it keeps the ignition in good shape in any car.

Thanks JB.
I am always able to move the steering wheel whenever I have the issue. I can remove the key, re-insert, and it works. May have to do it two or three times.

So it sounds like the EIS and the K40 are the most likely culprits.

When stuff like this happens, do codes get thrown? I haven't had the opportunity to check yet.

From research I've done, apparently low voltage can result in key not turning (this according to my indie). When I got the car home, after sitting a couple of days the battery voltage was 12.35v at 20F. It made me wonder what kind of low voltage would result in the key not turning.

The battery is at least five years old (the PO doesn't remember exactly when he replaced it). So I'm going to get it tested and just replace it if there's any doubt. Seems like a good variable to eliminate.

Example where key was the problem:

Smart key won't turn in ignition/EIS problem - Mercedes-Benz Forum