I've had this code more than anything else over the last 20 years. Fussed with checking resistance on the glow plugs about 3-4 years ago and finally took it in and they replaced a bank of glow plugs. It's back again. Bank 1... (Passenger side right) Ohmed all 4 GP's through valve cover harness and readings are .5 to .8 ohms. Not sure what else to do. If they are all testing within range what next?