Glow Plug Relay: Testing and Inspection
The diagnosis of the 
glow plug relay is part of the "Control Module System" and starts with the "On-Board Diagnostic System Check." This will determine if the system is operating correctly. If the glow plug system is not working properly, the 
On-Board Diagnostic System Check will direct diagnosis to a Diagnostic Trouble Code (DTC) tree table or to another system circuit. Refer to 
Diagnostic Tables / System Diagnostic Tables. 
Testing and Inspection