Does the e53 key send a security signal to crank?

[paramax55]

My 2001 needs a head gasket, so I fixed it today by buying a 2006. The new one is a minor basket case and I got it cheap because I was the only one who could make it run and drive. It has three keys.

What should be the "main" key I believe is aftermarket. It opens easily and has a cr2032 battery. The switches are trashed. Usually this key won't make the car crank. One time it made the car crank, but it wouldn't fire. Sometimes it makes the car crank and start fine. I'm pretty sure the battery is trashed.

The second key is just plastic, with no remote buttons, but it has a RFID (I assume) unit in a little slide-out tray. It starts the car without issues.

The third key is just a plastic emergency key of some sort and I haven't tried it yet.

I never ran into this issue with my other car because it only has one key, the battery is easy to replace, and I haven't really had any issues with it.

So does the key send a security signal like the old Chevy VAT system?

[wpoll]

The E53 does not use battery power in the key to send signals to the EWS (engine immobilser) system. It uses a radio frequency field around the key slot on the steering column to power a radio frequency ID chip (RFID) inside the key assembly, that then sends a unique ID signal to the EWS system. If the ID received by the EWS system is pre-programmed to be accepted, the EWS will allow the engine to start.

Again, the battery in the key plays no part in this process. The battery in the key is purely for the remote lock/unlock features, which are entirely seperate from the engine imobiliser system.

[paramax55]

OK. Thanks! At least I know what I am looking for now.

BTW... how much does a key cost from the staelership?

[Henn28]

The BMW Mini Parts Store was my go to store when I needed OE keys made. A couple hundred bucks if I recall for my a new E53 key that worked, right out of the box. I read recently that they don’t seem to be in business, or in the key business any longer tho, which is too bad, if so.

Not sure if GetBMWparts.com does keys, but I’d definitely check them. They usually have the best prices on BMW OE parts that I’ve found. Easy to work with too…they are part of BMW of Silver Spring MD from what I read.

[andrewwynn]

Intermittent key usually means either bad solder traces on the EWS ckt in the key or a bad ignition switch. If you have a working valet key (solid plastic grip no buttons) that works reliably you can repair the remote key safely.

You are describing non standard keys that seem to defy logic as if perhaps a key was taken apart and the chip is in the steering column.

Post photos of your keys.

The all plastic key is only to open the door. Referred to as a wallet key. It's to get in when the key is accidentally locked inside. I suppose if on purpose also applies. (say you are swimming lock the key inside keep plastic key in your swimsuit pocket)

Bmw made a key for e53 that has a replaceable battery but for a built on flashlight. I think an older version for pre e53 also could be paired but it's very not normal.

If you get crank no start = ews. If you get no crank it's more likely the ignition switch or the starter.

Do you get any weird happenings in the instrument panel or wipers? Especially if you enable the vanity mirror lights?


–awr–

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[workingonit]

I recently tried to order a Valet key (no remote capability, just works on manually unlocking the door, and in the ignition...it has no battery but does have the RFID chip inside) online, but they said I had to go to a dealership in person.

I took my title, insurance, and ID to a dealership and they ordered the key from BMW, for $90 with tax. I picked it up about a week later. Never asked about a full-function key, since mine still works; I'm going to replace the damaged shell with a new one, with a precut blade and new battery, and resolder the circuit board inside, and then move the guts to it.

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[paramax55]

My old e53 has a factory key. This newer e53 has one that feels like Chinesium. The wallet key and the valet key are the other two that came with the car. The Valet key seems to work without any problems. The key with the buttons worked once (if I remember correctly) but usually doesn't let the car even crank. I know I sound like an idiot, but the battery is bad AND someone cut the factory ground cable and put a ghetto, high-school type of connector on it. In a few days, I will have some of the major stuff sorted out but, until then, it's "get the jumper cables, check the ground, try the other key..."

[andrewwynn]

EWS doesn't stop the crank from my understanding.

When you have a freshly charged battery you should document what each key does.

If you can't crank that usually means a problem with the ignition switch not the key.

If you have the valet key near the broken key it will activate EWS


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[Clavurion]

Originally Posted by andrewwynn

EWS doesn't stop the crank from my understanding.

Yes it does. Terminal 50 (starter motor activation) goes from ignition switch to EWS module which has internal relay for this circuit. That relay is activated if code on key and EWS match. EWS and DME/DDE has a separate communication line with rolling code table. If the codes match it will allow fuel injection.

http://www.e38.org/EWS.pdf

[andrewwynn]

Thanks for the clarification!

So a legit key that rolling codes confused wiki crank no fuel, but a key with broken EWS circuit will not even crank. That i think matches the symptoms better.

With that update, if the button key won't crank, hold the valet key right next to the button key when it's in the ignition: if it will crank and especially start that indicates the EWS circuit in the button key has a bad solder joint.

–awr–

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