Set your multimeter to the lowest scale of resistance (we are going to check continuity) disconnect the harnesses from the valve cover gaskets. on each bank there will be 2 larger pins on the each side of the connector cavity. those are the glow plug pins there will be four in each cavity. check their restance to ground each should be 1-2 ohms and have continuity to ground (b-)

if they all check out the next thing would require a dealership scanner. you would want to perform a injector buzz test cold and see if the injectors are sticking cold.