How do I diagnose intermittent crank, no start caused by PATS?

[RussAdams]

My 1999 4.0 OHV 4x4 automatic is intermittently doing the PATS flashing THEFT crank/no start dance. It does not seem to make a difference if I put the key in slowly or fast when it shows the fast flashing THEFT light when it's acting up. The truck does start, eventually.

I've been reading all the threads I can find about this, but I am not sure exactly how to diagnose which part is failing.

The truck has over 240,000 miles and the ignition switch is quite warn/loose when I insert the key. LOADS of play.

How do I go about diagnosing which part is bad?

1. Can the ignition switch slop cause this? How do I tell if it's the ignition switch slop?
2. Is the PATS Ignition Immobilizer Module/Transceiver bad? Can it work only intermittently? How do I tell this is the problem?
3. Is the PATS module itself?

I did find and read Jim Oaks' great article. I just am unsure how to proceed.

Is there a good HOW TO on using Forscan to read the PATS error codes?

Thanks so much for any advice.

Russ

 

[2011Supercab]

Turn on the key and leave it on

Rapid flashing THEFT light will flash for 45-60seconds and THEN start to flash a trouble code, 2 digits with a 1 and then 1 to 6 flashes

11 Transceiver [transponder coil] not connected, or there is no power to it.
12 Transceiver internal fault.
13 No Key/no PATS key has been used to turn the ignition switch.
14 Incomplete key code received.
15 Invalid key code received.
16 CAN communications error.