What does it mean?
This code indicates that there is a failure in the glow plug circuit preventing the glow plug form operating normally. In a Diesel engine, there is no spark to ignite the air/fuel mixture. Instead the heat from compressing the mixture rapidly is enough to ignite the air/fuel mixture. Diesel engines need to first reach a good operating temperature before this is possible. Before the engine is warm it uses a glow plug to heat up the cylinder to enable the combustion of the air/fuel mixture. Without a glow plug combustion may not be possible in cooler temperatures.