And this surprises you ??? some things Engi-neers @ GM baffle the imagination, there is even a lift pump voltage monitor signal that can be seen on my MT2500 one would think absence of that would turn on the DTC,
Reminds me of a mounting pad of a gas turbine engine removal rail bulkhead storage mount, on a ship I once worked on 4 different fastener sizes/holes 1/4" to 3/4" to mount an aluminum rail, 4 different engineers none talking to the other ergo 4 different fasteners.