Hi guys,
Have a r53 with a key that had a loose solder connection and the key fob stopped working.

Replaced the battery and resoldered the connections.
Now the lock, unlock works, but the car won't start.

I was under the impression, possibly mistakenly, that the transceiver chip was in the key but was not powered by the battery. I figured this since the key would not unlock the car before, but would start.

I did try to start the car with the key only, once. Is there a security lockout that needs to be reset? Or could the chip have become damaged?

Thanks in advance.

 

The immobilizer chip is attached to the fob cover (not on the circuit board). There should have been little risk from what you did with the battery.
Photos here: https://www.northamericanmotoring.co...for-cheap.html

No reset is necessary. Does the car sound a ping warning when the key is close to the ignition switch (or inserted) and the drivers door is opened? That would indicate it detects an immobilizer chip.

 

Thanks for the quick reply,

When I insert the key shell, there is no chime, with the door open or closed.

The reason I thought it might be on the circuit board is after I took it apart, but before I replaced the battery, I when to leave, and the car did not start with the key shell, so I took the circuit board and held it close to the ignition and the car started.

 

 

 

Ok, so update.
After reading that other thread, it seems the chip is on the circuit board, but does not seem to be powered.
If I take the key shell, and have the circuit board in the car, when I insert the key, I get 4 chimes, but still no start.

 

I did disconnect and reconnect the battery just for a chance there might be a reset of some sort.

 

Sorry for my misinformation. I was looking at the wrong photo in the other thread.

You are correct. The immobilizer chip is attached to the circuit board, but just on a holder. It is an RFID chip that isn't powered.

So this doesn't work any more? Not sure what to make of it now. When you were soldering, how much heat might the chip have received? But it wasn't enough to damage the remote unlock.

 

That's odd. If the car chimes with the circuit board nearby it should start- the chimes mean the EWS chip is recognized. I think my car (R50 with older, two button style of key) chimes incessantly when the key is inserted if I don't close the door. Perhaps the 4 chimes are some sort of trouble code.

Did the coil of wire around the EWS chip get nicked or broken? Here's a key fob wall of shame from a BMW key repair place. These three button circuit boards are identical to yours; look to the bottom for info on the EWS chip and coil:

https://www.bmwgm5.com/KF_WoS.htm

One final thought- how good is your battery? When they are bad they very often won't even allow the starter motor to turn over.

Dr. Bruce Hart
MINI Key Hospital