Hi my name is John.
There is two relays for the glow plugs.
Here picture of where.
individual glow plug is used for each cylinder. Each
glow plug is threaded into the left side of the cylinder
head below the cylinder head cover/intake manifold.
Sometime you have to remove the fuel rail to unscrew the glow plugs.
The torque for the fuel rail is 24 ft lb.
first you disconnect the negitive battery
cable and than remove the engine cover.
You undo the bolts to remove the cover, here a picture for you.
Here how to remove the fuel rail if needed.
If the glow plug are on they are very hot.
You unplug the connector from the glow plug and unscrew it and just screw a new one if needed.
Let me know if you need more.
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Thank you for choosing just answer