Thanks. Yeah, it was sad to see it go, and frustrating to be unable to solve it.

Tried replacing the B+ wire and repinning the connectors for the immobilizer. If anything the car was worse afterwards, cutting out even when driving which it didn't do before.I considered reflashing the ECU, but it really wasn't worth anymore investment to us. Sadly it went to crusher. After 23 yea...

Very frustrated with this problem. First, fuel pressure is 60psi and steady. The only codes that ever show up are ECM720A and IMM321. They are intermittent though. Typically only about 30% of the time and I now feel they are just spurious, a results of starting a stalled engine many times with vario...

Wow, thank you for the response. The time it runs is variable and sometimes is long enough that I am about to celebrate and then it starts to stumble and then stall. Sometimes it won't even fire during cranking. Its highly variable. The fuel pressure seems good although I observe some variation betw...

Debugging continues. VIDA shows IMM-321 Faulty comms consistently. I am going to have to verify the wiring between the ECM and the immobilizer modules. VIDA shows the IMM is recognizing the key and giving a positive signal to start. At his point it looks like either wiring or the ECM itself is bad. ...

Thanks for the ideas. Based on what I've read and my own experience the immobilizer does not prevent starter cranking. It seems to cut the fuel pump based on my observations which is why it runs for a few seconds then quits.

Sounds familiar. You should get a P1670 if you try to start it enough times and it is the immobilizer. First thing I would try is pulling the antenna ring off the ignition and measuring it to see if its 5 ohms across the two inner pins. Also if you have another key try both of them.

As the title says I expected to conquer this one quickly with a new antenna ring but no such luck. Both keys tried and do not work. Cleaned the connector and back probed with connector attached confirming good 5.5 ohm connection to ring. With connector off read 75k ohms confirming wiring good to imm...

Very through and detailed write up. Some comments: On the NA version the fan, shroud, and relays can be left in place. Just bungee cord them to the engine to keep them out of the way. The STEM bolts have a separate nut on the top protruding part of the bolt through the welded frame nuts that is used...

The weak battery resetting the monitors on cranking bit me one year. If cranking voltage dips below 9V during cranking you likely will have trouble.