Replace Key Battery medium urgency

2024 Toyota 4Runner Dead Key Fob Battery: How to Get In, Start, and Replace It

If your 2024 Toyota 4Runner key fob suddenly won’t lock/unlock or the vehicle won’t detect the fob, the most common cause is a dead fob battery. The good news: you can still get in and start the 4Runner using the hidden mechanical key and the vehicle’s backup detection method. Then you can replace the battery in minutes.

Understanding Your Situation

The coin-cell battery inside the smart key fob has drained, so the fob can’t transmit a strong signal. The vehicle may show a “Key Not Detected”/similar warning, and the buttons may work intermittently or not at all.

🚀 Immediate Steps to Take

  1. Unlock the door with the hidden mechanical key: slide the release on the fob to remove the metal key, then use it in the driver’s door key cylinder.
  2. Start the 4Runner using the fob’s backup method: hold the Toyota emblem side of the fob against the START/STOP button (or as close as possible) and then press the brake and start the vehicle.
  3. Replace the fob battery as soon as practical (use a quality coin-cell battery and avoid touching the battery faces with bare fingers).

Your Options

DIY battery replacement (coin-cell)

Cost: $5-$15 Time: Same day

Open the key fob case carefully, remove the old coin-cell battery, and install a new one of the same type (match the marking on the old battery). Test lock/unlock and starting afterward.

âś“ Pros:
  • Lowest cost
  • Fast and convenient
  • No programming required for a simple battery swap
âś— Cons:
  • Risk of damaging the fob housing/clips if pried aggressively
  • Using the wrong battery type or installing it backwards can leave the fob nonfunctional

Battery replacement at a dealership parts/service counter

Cost: $10-$30 Time: Same day

A dealer can confirm the correct battery and may install it for you (policies vary). This is helpful if you’re unsure how to open the fob without damage.

âś“ Pros:
  • Correct battery type confirmed
  • Lower chance of breaking the fob case
  • Quick verification that the fob works after replacement
âś— Cons:
  • Higher cost than DIY
  • May require a visit during business hours

Mobile locksmith or roadside assistance (battery + basic check)

Cost: $50-$150 Time: Same day

A mobile tech can replace the fob battery where you are and verify the vehicle recognizes the key. Useful if you’re stranded or can’t access tools.

âś“ Pros:
  • On-site help if you’re stuck
  • Can help confirm it’s truly a battery issue (not a damaged fob)
âś— Cons:
  • Most expensive option for a simple battery
  • Availability and response times vary

⚠️ What to Avoid

✕ Don’t force the fob open with excessive prying—broken clips and cracked housings are common when using the wrong tool.

✕ Don’t install a different battery size/chemistry than what the fob specifies (match the exact marking on the old battery).

✕ Don’t assume it’s “not the battery” just because the fob worked yesterday—coin cells can fail suddenly, especially in cold weather.

⚠️ Common Mistakes to Avoid

  • Using wrong battery type
  • Damaging case during opening
  • Not resetting after replacement
  • Buying expensive batteries

Frequently Asked Questions

Can I still drive my 2024 Toyota 4Runner if the key fob battery is dead?

Yes. You can unlock the driver door with the hidden mechanical key and start the vehicle using the fob’s backup detection method by holding the fob against/very near the START/STOP button while starting.

Will I need to reprogram the key after replacing the key fob battery?

Typically, no. Replacing the coin-cell battery does not erase the key’s programming. If the fob still isn’t detected after a new battery, the battery may be installed incorrectly, the fob may be damaged, or there may be a vehicle-side issue.

How do I know which battery my 4Runner key fob uses?

Use the marking on the old battery as the source of truth (for example, it will be printed on the battery face). Buy the same type from a reputable brand and install it in the same orientation.

Why does my 4Runner say “Key Not Detected” even when the fob is in the cabin?

A weak/dead fob battery is the most common reason. Other causes include interference from electronics, the fob being too far from the start button, or a damaged fob. Try the backup start method (hold the fob to the start button) to confirm.

⏱️ Urgency Note: Low to moderate urgency: you can usually unlock and start using the backup methods, but replace the battery soon to avoid being locked out at an inconvenient time.

Related Information

Need Detailed Information?

Get vehicle-specific key fob compatibility, part numbers, and a complete price comparison for your 2024 Toyota 4Runner.

View 4Runner Key Fob Guide →

Last updated: 2026-01-04