I've got a 2006 Mazda 6 that has never had a problem. It's bone stock.

Today, when I went out to start it, it would crank, but not start.

It is cranking strongly - the battery is fully charged, and the battery is only about a month old.

While it is cranking, the security (car with key) light is flashing, and I can hear a relay clicking at the same time as it is flashing. This points me to immobilizer.

However, if the immobilizer is activated, I believe it should not crank at all.

I can insert the key and turn it to ON, the security light turns on, then turns off completely, as it normally does. As soon as I turn to START, the engine begins to crank, and the security light starts flashing.

The same thing happens with both keys.

I have tried disconnecting the battery and shorting battery leads together to clear anything in the ECM, with no effect. I have tried charging the battery to ensure it is fully charged.

I made a video of the car cranking and not starting:


Just as a side note, in case it matters, it is 30 degrees F (-1C) outside.

I also hooked up a code reader to the OBDII port, there were no codes. I tried clearing codes anyway, with no change.

Anyone have any suggestions as to what step I should take next?

 

I found the problem. The 15 amp fuel injector fuse in the engine compartment fuse bay had blown. Replacing the fuse fixed everything. Just posting in case someone has the same problem sometime down the road.