McLaren 540C key fob battery
1 of the 5 model years listed for the McLaren 540C have a proven battery. The most common answer is CR2032. Rows below run oldest to newest; a year can appear twice when the car came with more than one kind of key.
- 2016Smart key
CR2032
Owner's manual: manualslib.com (checked Nov 1, 2026)
Manual text: “You will require a single CR2032 3V battery.”
Find CR2032 on Amazon - 2017-2020Smart key
Not confirmed yet
Changing the battery
Smart key (push-button start)
- Start by freeing the hidden metal key: there is a latch or slide on the case, and the blade comes out once it moves.
- Look inside the empty key slot for a notch. Put the tip of the metal key or a small flat screwdriver wrapped in tape there and twist gently until the shell splits.
- Note which side of the old coin cell faces up (usually the side with the writing), lift it out with a plastic tool, and press the new one in the same way.
- Reassemble, refit the emergency key, and check that the car sees the fob when you press start.
A CR2032 is 20 mm across and 3.2 mm thick. CR2032, CR2025 and CR2016 share the same width but not the same thickness, so a swap between them can leave a loose contact or a case that will not close.
Coin cells are a choking and burn hazard for children. Store the spares in their original pack, out of reach.