Trans Prog Failsafe when cool outside. Battery? VR? Alternator? (N62)

[haigha]

I've searched and read a bunch of TPF threads but haven't seen one that matches my situation exactly.

2004 4.4 with 41k miles, garaged. On a Battery Tender Jr when it's in the garage since it's driven once or twice a week. Battery is now a little over two years old. Garage is not heated.

Four or five times last winter, as soon as I shifted the X5 out of park or was about halfway down my block, and the temperature was in the forties or below, I got the TPF error along with the 4x4 warning light. I think the DSC light too, a couple of times. The temporary solution was to let the car warm up to about halfway to due north on the oil temperature gauge and then restart the car. The errors would then go away and everything worked normally. I'm in the Southwest, so it does not get below freezing often. No problems in the spring, summer or early fall.

Three drain and replace ATF procedures, twice in late summer and yesterday. The mechatronic sleeve, magnets, gasket, plugs and filter were changed on the last one. Last two changes we added about 6.5 quarts of ATF at 86 F fluid temperature after going through the gears, monitored on a Foxwell 520 Pro. The transmission shifts smoothly.

I got the TPF and 4x4 errors again two weeks ago when it was in the forties. Before starting the engine, the battery was at 12.2V. I used the Foxwell and set the Live Data to monitor the oil temp, gearbox oil temp, battery voltage and voltage at the transmission. Strangely, until the engine warmed up the voltage was 11.2 at both places. Once the engine was warm, both jumped to 14.1. I restarted the engine and everything was fine. No Service Engine Soon light.

I saved the codes from the Foxwell last time, but couldn't find the file with them on the microSD card when I put it in my PC. There were codes for the transmission, alternator and several other modules. My guess is that they're related to the low voltage.

Since the problem only happens when the temperature is colder, does it seem like a battery problem or is there something in the voltage regulator or alternator that would malfunction when it's colder outside?