Another place to look is the ground from the engine/transmission on the drivers side, if this is loose of not making good contact, all kinds of gremlins show up. Temperature gage erratic, heat controls acting weirder than normal. fuel gage not reading correctly.
Easy to check & repair. 13MM bolt on frame, 17MM bolt on engine.
Before you jack up the engine be sure to disconnect the rubber turbo to air cleaner hose on those models with the big air cleaner or you will damage the hose.