FAQ
TL;DR: BMW E46 key coding has a max 5‑second ignition window, and “Ignition key in a maximum of 5 seconds.” [Elektroda, sebap, post #16812264]
Why it matters: This FAQ helps BMW 3‑Series E46 owners fix remotes that won’t unlock doors after battery work or failed coding.
Quick Facts
- Coding window: ignition on to off must be within 5 seconds for pairing to take. [Elektroda, sebap, post #16812264]
- Typical coding sequence uses three presses of the open button while holding the other key button. [Elektroda, niewierny20, post #16812240]
- Remote may work right after reconnecting the battery, then stop once the ignition is cycled. [Elektroda, niewierny20, post #16808843]
- Mechanical key turns a switch; the remote uses a radio receiver and electronic module. [Elektroda, emeryt2, post #16811111]
- Repeated battery disconnections create errors; use proper diagnostics instead. [Elektroda, sebap, post #16811117]
Why did my BMW E46 remote stop working after I disconnected the battery?
Battery pulls can reset modules and upset the remote’s learned state. In the thread, the remote worked after reconnecting power, then lost function once the ignition was switched on. That pattern points to coding not sticking or an electronic fault that surfaces after the first ignition cycle. Avoid more battery pulls and proceed with proper diagnostics before re-coding. This edge case often appears right after current measurements or fuse work, as described by the OP. [Elektroda, niewierny20, post #16808843]
How do I re-code a BMW E46 key fob correctly?
Use the short coding window. 1) Sit in the car; switch ignition to position 1, then off within 5 seconds. 2) Remove the key, hold one button, and press the other button three times. 3) Release and test. Ensure you release the held button after the three presses. Repeat only if needed. Sequence timing and button release order matter for the receiver to accept the rolling code. [Elektroda, sebap, post #16812264]
What exact button sequence did the OP try?
They turned the ignition to position 1, waited about 5 seconds, removed the key, held the BMW logo button, and pressed the open button three times. They also tried the reverse order (hold open, press the logo/close three times), with the car otherwise untouched and doors unlocked. It had worked before, but now fails to pair. This shows sequence alone isn’t always enough when a fault or timing issue exists. [Elektroda, niewierny20, post #16812240]
Do I need to release the button I’m holding during key coding?
Yes. After pressing the opening button three times, you must release the button you were holding. Holding it the entire time can prevent successful coding. Observing the press-and-release order is part of the accepted procedure for these remotes and was highlighted to correct the OP’s attempts. [Elektroda, sebap, post #16812264]
Should I keep disconnecting the battery to troubleshoot central locking?
No. Stop disconnecting the battery and run proper computer diagnostics instead. Repeated power cuts can create or mask faults and make troubleshooting harder. A scan saves time and prevents new error entries. As one expert advised: “do some computer diagnostics.” This is the fastest path to identifying module or key issues. [Elektroda, sebap, post #16811117]
What’s the difference between using the key in the door and using the remote?
The key in the door operates a mechanical switch that triggers locking. The remote relies on a radio receiver and an electronic comfort module to interpret signals. A mechanical lock can work while the electronic path fails, which explains why some cars unlock from the barrel but not from the fob. Different subsystems mean different failure modes. [Elektroda, emeryt2, post #16811111]
What if I follow the steps and the remote still won’t pair?
Suspect a faulty remote (“pilot”) if correct timing and sequence fail. The contributor’s assessment was concise: “I bet the pilot damage.” Before replacing modules, test or refurbish the key fob with a specialist. Hardware failure in the key can block pairing even when the car side is fine. [Elektroda, sebap, post #16813413]
Does clearing fault codes make the remote start working again?
No. Clearing codes alone did not restore remote operation in the case discussed. Errors were erased after earlier measurements and fuse work, yet the remote still failed. This indicates the root cause lies in coding/timing or a hardware fault, not just stored DTCs. Proceed with correct coding steps and hardware checks. [Elektroda, niewierny20, post #16811696]
Where might the problem be if both coding methods don’t work?
Look toward the key coding algorithm or a fault in the electronic module that processes the remote signal. An experienced member noted possible error in the coding approach or an issue within the electronic module, distinct from the mechanical lock. Diagnose that element before replacing parts. [Elektroda, emeryt2, post #16811111]
Is my key original, and who can verify or re-code it?
The OP confirmed an original key and planned to visit a key specialist for testing and coding. A qualified locksmith or “key man” can check the transmitter, battery health, and pairing. This service confirms whether the fob transmits and helps decide on repair or replacement. [Elektroda, niewierny20, post #16815585]
Why does the remote work right after reconnecting the battery but fail after turning the ignition?
That pattern shows the receiver accepts a temporary state after power-up, then rejects the key after the first ignition cycle. It points to coding not persisting or a component fault surfacing under normal run conditions. Re-code within the 5‑second window and test again. [Elektroda, niewierny20, post #16808843]
What single tip improves success when pairing an E46 key?
Control the timing. Perform the ignition on–off step within a maximum of 5 seconds, then use exactly three presses in the sequence. Many failed attempts come down to exceeding this tight window or not releasing the held button at the end. [Elektroda, sebap, post #16812264]
