Run Mode Change System Check

I have spent a week stuck on the side of the road, sleeping in my 2008 OBXT (5EAT), and pouring over this forum, others, and searching other sources for answers. I have the same symptoms as others when I try to start the car: ACC behaves normal, turn key onward to ON and gauges sweep and lamps test normally, but then radiator fans kick on, coolant temp gauge pegs, radio console and climate go dark. When I turn key to engage the starter, nothing. No click, no moan, no dimming. Then I see the message RUN MODE CHANGE SYSTEM CHECK on the dash.

When did it start? Well, after I pulled the intake manifold and the main engine harness to do some maintenanc and repair. I had a coolant leak, vAcuim leak, and a couple connectorsnin the harness that needed attention. The car has not started since.

I have taken each step offered here: Cleaned all grounds on the frame, engine block, heads, and paid very special attenttion to the harness ground luggs on the harness, which bolt to a dedicated spot on the Bank 2 fuel rail protector. Each of the grounds now show no more than .2mA of resistance.

I have removed the harness and reattached every connector, paying my close attention to each connector to make sure there are no broken wires or shorts.

Ensured. the CTS connector is not attached to the EVAP sensor, and vice versa. The connectors are almost identical and close enough that it is possible to mix them up. And, as I read here, the symptoms of mixing them up would mimic what I am seeing wrt gauge and fansb. Actually I tried both ways, same issue, and returned them to color coordinated state: grey connector to the grey CTS and black connector to the Black EVAP sensor;

Installed a new Red Optima AGM battery with 1000 CA, 800CCA, 50 Amp hour and 100 RC whatever that is. When I installed the battery it showed 12.7vdc across the terminals. One day later is it 12.2vdc. Parasitic Drain maybe? I have used the inside lights a bit, maybe a half

Hour tops. And have tried to start the car maybe 29 times in that span.

Reseated the main and secondary harness connectors. Reseated the transmission harnesses. And checked under the dash on both sides for loose connections.

I have cleaned the starter contacts, and made sure the transmission grounds are as sound as those up front.

I have continuity tested, reseated, and tested again every fuse in the car except for the airbag fuses. And I have pulled the starter relay and swapped it with the seat heater relay, which appears identical in shape, function and capacity.

As I am not gonna be going anywhere until

This is resolved, I should be able to take advise or answer questions readily. Any thoughts? Advice? Amusing anecdotes?

I have food and water. And unless it gets real cold, I’m I. Good

Shape. And I’m retired and single and nobody is expecting me home. Sort of liberating.

One other thing that seems odd: measuring voltage across the battery terminals shows 12.2vdc today, but if Indiaconnect the negative cable and measure voltage between the cable connector and the negative Battery terminal, I see 11.7vdc. Shouldn’t that reading be the same as across the terminals? Why the voltage drop? Help please.