Principle of operation
As common rail diesel engines have better cold-starting characteristics than traditional diesel engines, the glow plugs have two functions on this engine
Pre-heat stage
In this stage, the glow plugs function as normal, preheating the combustion chambers to aid cold starting.
After-glow stage
At engine speeds below 2,500 RPM, and at temperatures below 50 degrees C (122 degrees F), the glow plugs continue to heat the cylinders to improve idling and reduce emissions.
Warning light
The glow plug warning light on this vehicle not only informs the driver that the glow plugs are operating, but also as a malfunction indicator lamp (MIL) for the engine management system. For additional information, See Glow Plug System .