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2024 Acura MDX Key Fob Not Working? Quick Fixes, Costs, and Next Steps (US)

If your 2024 Acura MDX key fob suddenly won’t lock/unlock or the vehicle won’t detect it for push-button start, the cause is often power, signal interference, or a fob/vehicle communication issue. The good news: there are a few safe checks you can do immediately before paying for service.

Understanding Your Situation

Most “key fob not working” cases on a 2024 Acura MDX come from a weak/dead coin-cell battery, a fob that’s been damaged by moisture/impact, radio-frequency interference, or a vehicle-side issue (12V battery low, receiver/antenna problem, or a fault that needs diagnostics). Even if the remote buttons fail, the MDX can usually be started using the emergency start/backup detection method.

🚀 Immediate Steps to Take

  1. Try the backup start method: Sit in the MDX, press the brake, and hold the fob against/very close to the ENGINE START/STOP button, then press the button. (This uses the fob’s passive transponder even if the battery is weak.)
  2. Replace the key fob battery with the correct coin cell (commonly CR2032 on many Acura fobs—verify your owner’s manual or the battery marking). Install with clean, dry hands, confirm polarity, and test lock/unlock and remote start (if equipped).
  3. Rule out interference and vehicle power issues: Move away from other transmitters (parking garages, cell towers, other key fobs), remove the fob from metal containers/bags, and check the vehicle’s 12V battery condition if you’ve seen slow cranking, warning messages, or repeated “Keyless Access System Problem” alerts.

Your Options

Replace the key fob battery (DIY)

Cost: $3-$12 Time: Same day

Open the fob case, replace the coin-cell battery with a high-quality brand, reassemble, and test all functions (lock/unlock, tailgate, panic, remote start if equipped).

âś“ Pros:
  • Fastest and cheapest fix
  • Often resolves intermittent range or “key not detected” issues
âś— Cons:
  • Won’t fix a water-damaged or physically broken fob
  • Incorrect battery type or poor contact can cause continued failures

Use the backup start method and drive to service

Cost: $0 Time: Same day

If the fob won’t work remotely, use the emergency/backup detection method to start the MDX and get to a safe location or service provider.

âś“ Pros:
  • Lets you start the vehicle even with a weak fob battery
  • Avoids towing in many cases
âś— Cons:
  • Remote lock/unlock may still not work
  • If the fob is fully failed or missing, you may still be stranded

Dealer diagnostic + key fob testing

Cost: $150-$250 Time: Same day / 1-3 days

An Acura dealer checks for keyless access system faults, tests the fob signal, verifies software/TSBs, and confirms whether the issue is the fob, the vehicle receiver/antenna, or a low 12V battery.

âś“ Pros:
  • Accurate diagnosis for vehicle-side problems
  • Access to Acura-specific tools and updates
âś— Cons:
  • Diagnostic fees may apply even if you decline repairs
  • Scheduling may take time

Replace and program a new OEM Acura smart key fob (dealer)

Cost: $350-$650 Time: Same day / 1-3 days

Dealer supplies an OEM smart key fob and programs it to your 2024 MDX (and may erase lost/stolen keys from the vehicle memory). Proof of ownership is required.

âś“ Pros:
  • Most reliable compatibility and range
  • Can disable missing keys for security
âś— Cons:
  • Highest cost option
  • May require ordering parts and bringing all existing keys

Automotive locksmith: key fob replacement/programming (where supported)

Cost: $250-$500 Time: Same day / 1-2 days

A mobile locksmith may be able to supply and program a compatible fob and cut an emergency key blade (if applicable). Capability varies by region and model year.

âś“ Pros:
  • Often faster than a dealer appointment
  • Mobile service can reduce towing risk
âś— Cons:
  • Not all locksmiths can program 2024 Acura smart keys
  • Aftermarket fobs can have shorter range or reliability issues

Address vehicle 12V battery or charging issues

Cost: $0-$350 Time: Same day

If the MDX’s 12V battery is weak, the keyless access system may behave erratically. A battery test, replacement, or charging system check may be needed.

âś“ Pros:
  • Fixes a common root cause of keyless glitches
  • Improves overall reliability (starting, electronics)
âś— Cons:
  • Not the fix if the fob itself is damaged
  • May require resetting settings or relearning features after replacement

⚠️ What to Avoid

✕ Don’t force the fob case open with sharp tools—broken tabs and damaged seals can lead to moisture intrusion and permanent failure.

✕ Don’t keep pressing remote start repeatedly if the vehicle isn’t responding—confirm the MDX is in range, doors/hood are closed, and the fob battery is good to avoid confusion and unnecessary battery drain.

✕ Don’t buy the cheapest no-name aftermarket fob online without confirming FCC ID/part compatibility and return policy—incorrect or low-quality fobs often won’t program or have poor range.

⚠️ Common Mistakes to Avoid

  • Assuming key is broken
  • Not checking battery first
  • Calling tow truck immediately
  • Replacing when reprogramming needed

Frequently Asked Questions

Can I start my 2024 Acura MDX if the key fob battery is dead?

Usually, yes. Use the backup start method by holding the fob against/very close to the ENGINE START/STOP button while pressing the brake, then press the button. This allows the vehicle to read the fob’s passive chip even if the fob battery is weak or dead.

Why does my MDX say “Key Not Detected” even when the fob is inside?

Common causes include a weak fob battery, RF interference, the fob being blocked by metal objects, or a weak vehicle 12V battery. If a fresh fob battery and moving locations doesn’t help, the vehicle may need diagnostics for the keyless access system.

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

In most cases, no. Replacing the coin-cell battery should not erase programming. If the fob still doesn’t work after a correct battery install, the issue may be fob damage, poor battery contact, or a vehicle-side fault.

How much does a new key fob cost for a 2024 Acura MDX in the US?

Typical all-in pricing (fob + programming) is often around $350–$650 at a dealer, depending on region and whether additional keys are being added or erased. Some locksmiths may be less, but availability for 2024 models varies.

Will a low car battery affect the keyless entry and push-button start?

Yes. A weak 12V battery can cause intermittent keyless entry, warning messages, and inconsistent starting behavior. If you notice other electrical symptoms, have the 12V battery tested.

⏱️ Urgency Note: If you only have one working key fob, address the problem promptly—waiting can leave you stranded if the fob fails completely. If a fob is lost or stolen, have the MDX’s key memory updated/keys erased as soon as possible to reduce theft risk.

Related Information

Need Detailed Information?

Get vehicle-specific key fob compatibility, part numbers, and a complete price comparison for your 2024 Acura MDX.

View MDX Key Fob Guide →

Last updated: 2026-01-04