Hi, apologies if this is a repost but I tried searching the forum and around the internet to see what if I could find anything already.
Got a 2007 Honda Fit with ~160k miles. This is my first car so I've been learning a lot - It wasn't taken very well care of before I got it so I've mostly been replacing the usual matenience painpoints like the spark plugs, coil packs, alternator, serpentine belt. It was running well one night but then the next day, it's only cranking and the engine won't turn over to start. The battery is fine as it will go into accessory mode just fine and it has plenty of fuel and we tried spraying starter fluid while starting it.
So we took out the spark plugs to check if it was sparking while starting, and it seems to not be. This is really strange to me as both the coil packs and the spark plugs are brand new, and have been working fine for about a month. What steps do I have to take to figure out where it isn't sparking?

 

I'm having the same type of issue let me know what you find out.

 

If it's "cranking" then the motor must be turning over. Otherwise the starter is not engaging the flywheel and you'll get a loud electric motor sound. If neither, then your starter is not doing it's job for some reason.

 

Figured it out! I feel like I should have seen this before, but again, new to cars... the green flashing key icon flashed for longer than 3s in accessory mode indicating that my immobilizer was active. I had done a shell swap to my key fob since it was super old, and in the process I configured the fob battery so it could access the part of the key that does remote unlocking but not the part of the key that tells the car that it is a valid programmed key. I took the key apart, washed the connectors with alcohol, made sure to put it together properly, and now it starts up again!