Got a 2006 F150 4.2 V6. Cranks over but no spark.
There is a little red light on the left side of the dash. It is flashing approximately once every second and a half. Does this mean that the security system has been triggered?

 

that’s what it does when off (key removed).

describe what it does when you put key in ingnjtion and turn it to on (before turning to start).

 

It lights up steady for a few seconds then shuts off.

 

I'm pretty sure if the pats system was not happy you would get a no crank condition.

If there's no spark, check to see if any fuses for PCM, etc are blown. Check the crank position sensor.

 

Agreed, and check the grounds in both kick panels
Check the codes

 

The only diagnostic codes I'm getting are O2 sensor heater circuits, both banks, sensor 2. O2 sensor stuck lean, both banks, sensor 2. Fuel trim system too lean, both banks. And cylinder head over temp protection active.
I don't think any of those will cause a loss of spark.
The tach needle moves when I crank it over. I'm pretty sure that means the crank sensor is still good.
I guess the next step is to check fuses and the grounds.

 

I got it started folks.
The coil pack fuse was blown.
I appreciate the assistance. I'm sure that I will be back with more questions before I am done with this POS.

 

Make sure the two ignition suppressor capacitors are in good shape and the wires leading to them are okay
One on each head at the front, single wire going to each

 

Not sure if this helps your situation or not but there's a fuel shut off button next to the fuse box in the cab on the passenger side. Something tripped that button on me once while I was at gas station on a road trip. Engine would crank but it wouldn't turn over. I've always had a hard time trying to find it because of the awkward location of the fuse box but if you're facing the fuse box it would be on the left side (front side of the truck) and the button is oriented in a way that when pressing it you're going in an up&down motion not a side to side.. If that makes any sense. I had to feel around for the button but once I found it my truck fired right up.