The one thing I have been doing different is parking in the garage (wife is not too happy about that of course, ha). I do plan to park it back out in the elements on the next hard cold we get, as long as its not a workday, in order to see if my theory of some sort of coolant/engine temp sensor could be an issue.
An ECT sensor problem cannot cause a no crank. But these issues can:
#PIC5234: Intermittent No Crank No Start With No DTCs - (Sep 1, 2009)
Subject: Intermittent No Crank No Start with no DTCs
Models: 2008-2010 Chevrolet Malibu
2007-2010 Pontiac G6
2007-2010 Saturn Aura
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Intermittent No Crank No Start.
A customer or technician may comment on the above condition. This could be the result of any of the following:
Misadjusted or damaged transmission shift cable. Park Neutral (PN) switch installation or internal failure. Loose or broken battery ground cable to ground stud (mostly on the 3.5L engine on the ground stud on the trans) Loose or damaged cable at the B+ post at the starter.
Follow the below steps to determine the root cause and necessary repair.
Carefully inspect transmission shift cable for any signs of damage. Replace cable if any damage is found.
Check transmission shifter and cable adjustment
In an attempt to duplicate the condition try shifting from any shifter position into the park position carefully, not slamming it in park. After shifting in to park try starting vehicle. If the vehicle does not start unless you push the shifter hard in to park you will need to adjust the shift cable as described (09077A)
Check output from Park Neutral switch to ECM for proper signal. Check all terminals for loose or poor connections at Park Neutral switch and ECM. If all appear okay replace the Park Neutral switch.
Loose or damaged nut/cable at the B+ post on the starter. (PIC5100) If post is damaged the starter will need to be replaced.
Loose battery ground at the ground stud. This issue is mostly been seen on the 3.5L engine, however some cases on 4 cylinder also. Check for loose connection between terminal and stud. Check for poor crimp between the terminal end and the cable. Check for broken cable strands at the crimp which may create high resistance. Replace the ground cable if a poor crimp is found or the cable has any sign of damage. If fastener is loose tighten fastener to proper torque.
Poor terminal connection at ECM or UBEC. Remove and do a terminal inspection and lube as per TSB (08-05-22-009A)
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.