A key with two jobs
A transponder key does two things: its blade turns the locks mechanically, and its chip answers the car’s immobilizer electronically. When you turn the key, a coil around the ignition reads the chip’s ID. Match the trusted list — engine starts. No match — the car stays silent, even with a perfectly cut blade.
That’s why a hardware-store copy of a chip key opens the door but won’t start the car: the copy has the blade and not the conversation.
Transponder key vs. key fob
The terms get tangled. A transponder key is a key with a chip in its head. A fob is the remote — buttons for lock, unlock, trunk — which on modern cars also contains a chip and often replaces the blade entirely with push-to-start. Older cars commonly have both: a chip key for the ignition and a separate fob for the doors.
Programming either one is a vehicle-side job; our programming guide explains why the car has to learn the new key.
When transponder keys need help
Lost keys (see all-keys-lost replacement), a chip damaged by water or a cracked key head, or a spare made the smart way — while a working key exists, per the spare rule. A chip key that starts the car only sometimes is telling you the chip or the reader ring is weakening; that’s the cheap moment to act.
How this article connects
- ✓Car Key Replacement — the service page
- ✓Key Fob Programming
- ✓Spare Keys & Duplicates
- ✓How Keys Are Cut to Code
Car key replacement, and every variant around it
The searches behind this guide, in one place: car key replacement, a lost car key, a car key fob that stopped working, key programming for push-to-start fobs, a transponder key, a spare car key, car key cutting to code, and a broken car key extracted without damage. One mobile visit handles the full set — call (561) 366-2611 and we will schedule your appointment.