Recently ran into an issue with my 2010 Mazda3.


  • Very cold day
  • After driving, the car cooled down
  • Car wouldn’t start (no attempt, no clicking, nothing)
  • Security light (immobilizer) on dashboard (car with a lock on it) fast-blinks (eg: 2 blinks per second)


  • Some water vapour leaked into the Main Relay (R14 in the engine fuse box)
  • As the relay was in use, it heated up, and the vapour condensed
  • As the relay cooled back down below freezing, the condensed water froze
  • When you attempt to start the car, the moving parts in the relay cannot operate because it is frozen in place


  • Take out the Main Relay, warm it up, reinstall, and start car
  • Or wait until the condensed vapour evaporates (for me it was about 1.5 hours after I turned it off)

To test if this is your problem:

  • Run car for 5 min
  • Turn off, wait 30 minutes
  • Try to start car (should fail with fast-blinking security light)
  • Remove Main Relay, warm up, then reinstall and start car


  • Replace the Main Relay. It is a $13 part and very quick and easy to change.

The relay in question is part number LF68-18-811 (replaced with part number LF69-18-811): Main Relay

FoMoCo is Ford Motor Company, and this is a common part, so there are likely a lot of cars impacted by this issue.

In my research, I found others with problems, Mazdas 2004-2009, but no 2010s:

Mazda TSBs (for vehicles of other years):