Key issue?

[paddy wright]

Until recently I thought my key battery had died but when I put a new battery on the car it worked perfectly again. Until Sunday when at Zedfest it decided it would be temperamental and now won’t work remotely again. Any ideas. Can’t see it being the GM5 as it went back to perfect with the new car battery.

 

[danfrost89]

Mine's a bit random like this - I suspect the battery is on its way out so I've just replaced the one in my spare key. I'll make sure that works first and then do my 'main' key.

My AI (pointed at forums, etc but still occasionally talks nonsense) suggests this thread:

T

Thread 'Key fob lock button works but doesn't...'

Oct 5, 2018

I recently got around to fixing my "dead" second key - soldered in a new battery, and did the reset sequence. All is well and functional except locking.

Pressing the BMW roundel button does not lock the car. My first thought was the button or circuit for it is dead but realised that in order to successfully execute the reset sequence, that button had to have worked :| To my caveman eyes, the circuit board connections seem to look fine. Don't know about the chip looking things tho (ok I'm not qualified to make a judgement on the circuit board lol).

Thoughts? I'm thinking of getting the...

• tomrdy
• Replies: 7
• Forum: E85 - E86 Problems

Summary :
Quick check: does unlock still work and only lock is dead? When the fob senses its own battery is low, BMW's system blocks the lock command only and lets everything else work — it clears once the key reads OK voltage 5 times running.

Fix: charge the key in the ignition (position 1) for 30–90 mins, then cycle it in and out to position 1 a few times to reset it. Workaround meanwhile: double-tap unlock, then immediately hit lock.

If a spare key works fine, it's just that fob. And if it keeps coming back after charging, the fob's rechargeable cell is dead — it's a soldered VL2020 inside that needs replacing.