Free DIY key fob help

Fix your key fob in minutes, not at the dealer

Battery swaps, “key not detected” errors, low battery warnings and resets, explained step by step for your car brand.

Popular: Replace battery Low battery warning Key not detected CR2032 vs CR2025

What’s happening with your key fob?

Pick the symptom and go straight to the fix.

Battery is dyingRange dropping or buttons need several presses. Swap the cell in 5 minutes.Replace the battery → Fob not workingDead, damaged or unresponsive fob. Work through the checks in order.Troubleshoot it → “Key not detected”Message on the dash after a battery change? Usually a quick fix.Fix the warning → Low battery warning stays onNew battery, same warning. Here is why it happens and how to clear it.Clear the warning → Needs a resetFob lost sync with the car? Resync or reset it without guesswork.Reset your fob → Lost your car keyYour options and what a replacement usually involves, by brand.See your options →

Change a key fob battery in 3 steps

The same basic method works on most fobs.

  1. Open the caseFind the small slot or release button. A coin or flat tool usually opens it without scratches.
  2. Match the battery codeRead the code on the old cell (for example CR2032) and fit the same size with the + side the same way up.
  3. Close and testSnap the case shut and try lock, unlock and start. Some cars need a quick resync.

Read the full step-by-step guide →

Battery guides by car brand

Opening the case and the battery size differ by make. Pick yours.

Toyota Honda Ford Chevrolet Nissan Hyundai Kia Jeep Subaru Mazda Volkswagen BMW Mercedes-Benz Lexus Acura All brands →

Most-read guides

What other drivers are fixing right now.

All key fob guides →
BatteryHow to Replace a Key Fob Battery: Step by Step BatteryHow Long Do Key Fob Batteries Last? BatteryCR2032 vs CR2025: Can You Swap Them? FixLow Battery Warning Won’t Go Away After a New Battery FixCar Key Not Detected After Battery Change ResetHow to Reset a Car Key Fob Without Guesswork

Battery size chart

Which battery does my key fob take?

The code on the old battery tells you the size. These are the ones you will meet most often in car key fobs.

Open the full chart →
BatteryDiameterThickness
CR203220 mm3.2 mm
CR202520 mm2.5 mm
CR201620 mm1.6 mm
CR163216 mm3.2 mm
CR162016 mm2.0 mm
CR245024.5 mm5.0 mm

Beyond the key fob

Guides for the rest of your car’s electrics.

OBD2 how-to guidesRead codes, check readiness, connect a Bluetooth scanner. Best OBD2 scannersBuying guides for every budget and car. Car batteriesTesting, registering and replacing a car battery.

Quick questions

What battery does a car key fob use?

Most use a 3 V lithium coin cell. CR2032 is the most common, followed by CR2025, CR2016 and CR1632. Check the code on your old battery to be sure.

How do I know my key fob battery is low?

Shorter range, buttons that need several presses, a flickering LED or a “key battery low” message on the dash are the usual signs.

Do I need to reprogram the fob after changing the battery?

Usually not. Most fobs keep their programming. Some cars need a short resync, which our reset guide walks through.

Can I start the car if the fob battery is dead?

Most push-button cars let you start with a dead fob by holding it against the start button or a marked spot. Your owner’s manual shows where.

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