Q: Hard start and Code P0672 - Low circuit on cylinder 8 glow plug

Hello. Code P0672 is the code for a low circuit on glow plug #2. If you are also having an issue with the cylinder 8 glow plug, then both of these issues, together, could be a potential cause for hard starting. The specific purpose of glow plugs is to warm the engine’s cylinders, in order to help make the engine easier to start. As diesel engines do not have a traditional ignition system and rely entirely on temperature and compression to ignite the fuel mixture, if there is any issue with the plugs, or their circuits, the engine may have trouble starting. I would test the glow plug circuits for cylinders 2 and 8 to see if there is an issue, if not with the plugs themselves, then with the circuits or wiring. If you need an official diagnosis of this, a certified technician from YourMechanic can come to your car’s location to inspect the hard start so that this can be repaired correctly.