Question 1

How do I spot a fake or underqualified locksmith before something goes wrong?

Accepted Answer

Three things tell you fast. First, they cannot give you a price range for your specific vehicle on the phone. Second, no visible company branding on the vehicle and no straight answer when you ask for their license number. Third, they push cash-only hard before they have even looked at the car.

For a BMW specifically, ask them which module handles key authorization on your generation. A qualified tech will answer that without hesitating. One who is guessing will pivot to something vague about "the computer." BMW key work done wrong does not just fail, it can leave a module in a state that costs significantly more to recover. The right person will explain what they are doing and why before they touch anything.

Question 2

What exactly is a remote head key and how does it work on a 2002 BMW 3 Series?

Accepted Answer

It is a single unit that combines two separate functions into one piece of hardware. The blade cuts to your car's lock cylinders and ignition. The head houses the transponder, which communicates with the immobilizer when you turn the key, and the remote circuit, which handles the three-button wireless functions when you press them.

Those two functions are independent. The remote runs on the CR2032. The transponder draws power from the ignition field itself, so it does not need the battery at all to let the car start. That is why a dead CR2032 kills your lock and unlock buttons but the car still fires up normally. They are in the same shell but they are not the same system.

Question 3

What tools do you actually use to program a key for this BMW?

Accepted Answer

For this generation, the job calls for professional BMW-capable diagnostic equipment that can read and write key data through the OBD port. On all-keys-lost situations, where there is no working key left to reference, the process goes deeper. That can mean reading the module directly, which requires tools that go beyond basic code readers.

I carry multiple platforms because no single tool handles every scenario cleanly on European vehicles. The techs on BMW forums are consistent about this: one underpowered tool trying to force a write it is not rated for is how modules get corrupted. I would rather spend the extra setup time doing it right than hand someone back a car with a new problem I created.

Question 4

My 2002 BMW 3 Series shows a key warning on the dash but the car still starts. What does that mean?

Accepted Answer

On this generation, a key-not-detected warning that appears while the car still starts usually points to a transponder read that is intermittent rather than fully failed. The immobilizer is seeing the key sometimes and not others. Common causes are a worn key blade that is sitting slightly off in the ignition, a weakening transponder signal, or debris in the ignition cylinder affecting the read position.

Do not ignore it. Intermittent reads have a way of becoming no-reads, and an all-keys-lost situation on a BMW takes significantly more time and equipment to resolve than a straightforward replacement while you still have a working key in hand.

Question 5

Can I buy a replacement key online and just have it cut, or does it need to be programmed?

Accepted Answer

Cutting alone is not enough. The replacement key has to be programmed to the immobilizer before it will start the car. An unprogrammed key will turn in the ignition and do nothing. So yes, you can source a key beforehand, but the programming step is not optional and it requires proper equipment. If you go that route, just confirm the key you are buying matches the factory FCC ID on your original fob before you spend anything.

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