Many u-codes can be contributed to broken wiring, shorted wiring, loss of the GM LAN circuits caused by various modules that communicate on the LAN. Just watched a video last night about a Chevy truck that had several electrical codes and they ultimately found a broken wire on the oil pressure switch that brought down the 5V reference line going to the sensor. Once the line was spliced back together again, all was OK. Shorted wiring, broken wiring is quite common in our trucks.
2008 Silverado LT, CCLB, Edge Insight CTS
2009 Arctic Fox 29-5T, Silver Fox Edition, Onan 3600 LPG generator