The owner of a 2007-09 Dodge Dakota with a 3.7-liter engine and 42RLE automatic may come into your store with a complaint that the transmission won't shift out of second gear after an engine start.
With a little prodding, he might admit that the problem is intermittent, with the transmission behaving fine on the next key cycle. The Check Engine light will be off and no trouble codes stored when either scenario presents itself.
One likely cause for the trouble, reports Chrysler, is the PCM at times incorrectly determining that certain operating parameters aren't being met following an engine start. That forces the transmission into "limp-in" mode, which causes the second gear lock situation. On the next restart, the module reverses itself, allowing the transmission to shift normally. Software gremlins in the PCM are what ultimately causes all the headaches.
Reprogramming the module with updated software is the only surefire fix. Check with a dealer for the specifics of the flash.