MX5 Miata Tech Forum

Keyfog not working (with new battery)

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Grouch Hal Smith
Citrus Heights, CA, USA   USA
2011 Mazda MX-5 "My Baby"
My backup keyfob doesn't work, so replaced the battery. IT STILL WON'T WORK! Any suggestions (other than pay BIG money for a new one from the dealer/factory? Is there a code or something else that has to be done with it?

Edited 1 time(s). Last edit at 2018-03-15 01:47 PM by Grouch.

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davzway David W
Fort McCoy, FL, USA   USA
Have you checked the coin battery to see if 'new' battery is charged? Many battery retailers sell OLD stock until gone, and having just received 'NEW battery, CR2025 for latest Mazda Advanced Keyless system.,, NOTHING on the package of FIVE (5) batteries says anything on date,, back has copyright date of 2016 but nothing on expiration date, Will be checking CR2025 on battery tester when back from trip.. Did go nearly six years on one and seven on other keyfob for 2011 Miata before the 'fob' stopped working.

Having CHECKED EVERY FUSE (BOTH inside and outside fuse box) for bad fuse, and checking Coin Battery being fully charged, and NEW battery in car, and IF KEYLESS ENTRY SYSTEM still doesn't work, may need to go to dealer to track down the problem.

Could check if there is a 'CODE' for the keyless entry system and having the plug in TESTING Equp, might be able to check yourself, fixing another issue.

1. Battery can go bad instantly, working one minute and not the next. Same goes ESPECIALLY for KeyFob (or any electronic device), working one minute then quits, REAL bad issue is electrical problems that are INTERMITTENT ,, then it needs to NOT work while on test bench to EVEN FIND out or hope to find what is wrong.. sometimes cost of doing so. exceeds value of object having issues.
2. Key Fob battery checked, if GOOD put in Key Fob, not working try MULTIPLE battery, and IF multiple GOOD batteries still don't make Key Fob work, ODDS are problem is elsewhere, NOT Key Fob, then it's CAR SYSTEM the Key Fob should actuate... first place is FUSE,, dealer should be able to advise WHAT CIRCUIT OR COMBINATION OF CIRCUITS that the Key Fob works to turn car on etc. Even if fuses LOOK good, replace ONE or BOTH Fuses on Key Fob circuits ,, 'Key Fob not working/ turning car on or unlocking door,, .......... REPLACE FUSES A SECOND TIME. IF that still doesn't do the job, may need DEALER or Mechanic with Computer Equip to check car as replacing Key Fob is NOT very likely to be the problem

THE TECH IS GREAT WHEN IT WORKS,, MORE TECH, MR. MURPHY (of Murphy's Law fame) has more chances to mess things up, and FUBAR chances are greater. Logic and Reason, there IS A REASON behind the problem and WHY.

Edited 1 time(s). Last edit at 2018-04-05 01:37 PM by davzway.

cdice Avatar
cdice George Dice
They do stop working. Do a search on Ebay or Google. A number of sellers take the guts from a used junkyard fob and put it in a new case and sell it for much less than a dealer does.

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