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Duramax LLY – GLOW PLUG OPERATION AND TESTING

The engine glow plugs are used to heat air entering the combustion chamber. Heating the air results in improved cold temperature starting and engine warm-up.

A total of eight glow plugs are used; one for each cylinder.
Each glow plug is threaded into a cylinder head port located just below the injector nozzle (Figure 2-5). The tip of each plug extends into a pre-chamber which concentrates the fuel/air mixture prior to combustion.

The glow plugs are operated by a relay mounted on a bracket attached to the right side intake manifold. The relay is in circuit with the ignition switch and is energized only when the switch is in the “start” and “run” positions.

Turning the ignition switch to the “start” position allows current to flow through the switch to the relay and the PCM. Once energized, the PCM uses information from the coolant temperature sensor and the intake air temperature sensor to determine glow plug “on time”. The PCM commands the relay to allow current to flow through it and to the individual glow plugs and monitors each glow plug circuit voltage individually. If a glow plug failure is detected, a DTC P0380 will be set.

 

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