Glow Plug System - Glow Plug System
Description and Operation
COMPONENT LOCATION
Item
Part Number
Description
1
-
Glow plugs
2
-
Glow plug warning indicator lamp
3
-
BJB
OVERVIEW
A glow plug is installed in the inlet side of each cylinder, to heat the combustion chambers before and during cranking.
This aids cold starting, reduces emissions and engine noise when idling from a cold engine.
A wiring harness on each bank of glow plugs is connected to a separate relay and fusible link in the BJB (battery junction
box) . Each glow plug is grounded through its fixing in the cylinder head. Operation of the glow plug relays is controlled by
the ECM , which also controls the illumination of the glow plug indicator in the instrument cluster.
Each glow plug is a tubular heating element which contains a spiral filament encased in magnesium oxide powder. At the
tip of the tubular heating element is the heater coil. Behind the heater coil, and connected in series, is a control coil. The
control coil regulates the current to the heater coil to safeguard against overheating.
OPERATION
There are three phases of glow plug heating: Pre heating, crank heating and post heating. The ECM (engine control
module) determines the heating times from the ECT (engine coolant temperature) . The lower the ECT (engine coolant
temperature) , the longer the heating times.
When the ignition switch is switched to mode II, the ECM (engine control module) calculates any required heating times
and, if heating is required, energizes the glow plug relays in the BJB (battery junction box) . W hen pre heating is required,
the ECM (engine control module) also sends a message to the instrument cluster, on the high speed CAN (controller area
network) bus, to request illumination of the glow plug indicator. The glow plug indicator remains illuminated for the
duration of the pre heating phase, or until the ignition switch is turned to the crank position, whichever occurs first. If
required, the ECM (engine control module) keeps the glow plug relays energized during cranking and for the duration of any
post heating phase.
The ECM (engine control module) monitors the drive circuit of the glow plug relays for plausibility of operation, continuity,
and short and open circuits. If a fault is detected, the ECM (engine control module) stores a related fault code and
permanently illuminates the glow plug indicator while the ignition switch is in mode II.
CONTROL DIAGRAM