I bought my 2010 Fit in spring of 2022, and put only 500 miles on it. Why? because the immobilizer system would keep the car from starting. I was initially able to get it to start, but the problem got worse over time (corroded connection?).
I tried two other ECM's, two other immobilizer modules, instrument cluster, MICU, and jumpered the FI and ignition relays (worked on Gen 1). I finally gave up and had it towed to a competent shop. After 4 weeks, found the issue. It was a bad instrument cluster, compounded by breaks in the wiring harness between the ECM and MICU, and MICU and instrument cluster.

I did a search through the forums, and found other people with my same issue, but no one seemed to have posted their fix - or they got rid of their car. My bit of advice to anyone having similar problems to take it to the shop before the car won't start anymore.

 

I'm having this issue right now, 2011 Fit.

For a long time my car took an extra crank and I was never sure what it was, I thought it might be the spark plugs that needed to be fixed. However, I recently started having the issue with my immobilizer system. The car will still start and run after like 5-10 tries and if am out and starting/stopping my car it will be just fine. But in the morning or if it is the first time of day I'll have the immobilizer system issue.

I replaced the battery in the key fob, didn't fix. I got my battery re-charged and fixed, didn't fix. Not sure what to do now.

 

Why did it take 5-10 tries? Was the green key light on the dashboard flashing that led you to believe it's an immobilizer issue? The green light flashing will cut off the fuel and spark.

If the green light goes off, but it takes 5-10 times cranking for the engine to start, then you might have a leaky fuel injector. The injector floods the cylinder so it has a hard time starting, but cranking it a few times will clear out the excess gas. So if you leave the car idle for too long, then the gas seeps into the cylinder - such as when you leave it overnight. But if you're running around town, there's not enough time for the cylinder to flood, so you can start it normally.

 

Yeah the green key light flashes on the dash. I took it to the Honda Dealer and they cut me a new factory key since mine as aftermarket but were unable to reprogram it and said it could be something electrical, some unit/module, or the aftermarket radio I have. They quoted me at 160/hr and other places are quoting me the same which is just outrageous. I don't know what to do.

 

Yes, I went throught the parts cannon, and nothing worked. Changed the MICU, ECU, Immobilizer, instrument cluster, programmed extra remotes; nothing worked.
I think the car has a wiring defect from the factory that causes bad connection. I was able to program it, but a few days later, it would stop working. I finally had it towed to a mechanic who knows how to trace electrical problems. If you are in Baldwin, LI, the shop that fixed my car is in Corona, Queens - 3G Service Station. They has my car for 4 weeks, but they got it fixed, and it was way less than the dealer. I'm sure they're very familiar with Honda Fits after working on my car.