No spark
 

I have a 2004 S80, 2.9 six engine. It cranks fine, but no spark.

When I bought it, it would sometimes start, once running it ran fine. Had a code for crank position sensor, I replaced the crank position sensor. Also found the 2 wires at the connector twisted together and making contact. I fixed the wiring for the crank sensor, figured that would help. Also bought a used engine ECU, and replaced that.
Now it won't start at all. I then replaced the cam position sensor, no change. I also re-routed the starter power cable away from the crank and cam sensors.

I removed a spark plug and confirmed no spark.

While cranking, my scanner does pick up RPM, so something is working.

I thought the immobilizer will stop the starter, can it stop just spark? Is there a way to eliminate the immobilizer?

read up on the antenna ring problem and similar causes for no start. There are also relays to check as well.

The starter works, and the starter and ECU relays are the same, so I swapped those, no change. I used a volt meter to see if I get power to the ECU relay when the key is turned, and that is good.

I might not be getting fuel either, didn't come up with a good way to check that, although I do have fuel pressure. Not sure if the injectors are doing anything while cranking the starter.

Next thing to try, ignition switch. It just seems like something isn't turned on.... When it would start, it was random but once it started it seemed to run fine.

Everything I read the immobilizer will keep the starter from working. I did try locking and un-locking with the remote 5 times anyhow, no change.

It would sometimes work, now nothing, well just the starter.

I replaced the ignition switch, of course no change.

I wish I could trace the wires from the ignition switch, but can't seem to find a wiring diagram that has the ignition switch.

The starter works, but nothing else seems to work.

I replaced the under hood fuse / relay board, now it starts, sometimes. Once started, it idles fine, and seems to run ok.

Problem, if I run the RPM above 1,500 it throws code 5200 which seems to be crank sensor, which I already replaced. Could I have a weak new sensor?

Or could it be that the sensor ring on the flywheel is rusty?