There is a ground that goes from the drivers battery right to the drivers fender on a 10mm bolt. It's a common place for loose or weak connection to the ECM. It spices off into three individual ECM branch ground wires. Common cause of 2509 among others.
The most common cause is actually plain old low voltage caused by batteries, connections, cables, or excessive load like the grid heaters sticking on.
The grid heaters should cycle at 59 or 61 degrees and lower three or four times. Also going faster than 15mph turns them off. Sometimes one or both stick depending on year you might only have 1. I think 06 went to 1 it connects directly to the passenger battery positive. They draw 90 amps each so about what the starter does. Check with a volt meter or just disconnect to see if they/it are sticking.
The other common one is the big red battery crossover cable that connects the two battery positives. They get corroded inside the wire under the sheath within 4 inches of the drivers battery connection.
Check charging voltage at each battery to help confirm it.
Use a wire brush and scotch brite on both batteries connections until shiney.
The ecm uses the drivers battery for sense voltage. It controls the alternator field that then charges the passenger battery direct then through the crossover cable to the drivers battery.
If the crossover or drivers positive is bad it will overcharge the passenger until it blows up.
