is to improve combu st ion for low emissions an d to
achieve easy st arting at low temper atures.
OPERATION
When the ignit ion key is turned t o the ON posi-
tion, the glow plug output st age and pre-glow indica -
tor lamp are actu ated by the E CM. The duration of
the signa l depen ds on the coolant t empera ture. The
glow plug relay has pr ocessing tha t commu nica tes
with the ECM. If n o data exchange occurs a t the trig-
gering stage, th e preh eating is switched off after 2
seconds.
St art glowin g is initia ted when th e key is in t he
st art position. The glow plu gs (R13–R17) continue to
be su pplied with volt age. This ma kes it possible t o
st abilize the cold startin g speed. (After glowin g is ini-
tia ted when the st arter reject speed is rea ched).
After the engine sta rts, the ECM determines the
after glow per iod in line with coolant t empera ture. If
no signal is received from th e coolan t tempera ture
sensor, a fterglow is mainta ined for t hirt y seconds.
The following aim s a re reached by the afterglow :
• Improvemen t in warming-up proper ties
• Prevention of whit e exhaust smoke after cold
star t
• Stabilizing of th e cold sta rting speed
The glow plu g ou tput sta ge const antly sign als th e
curren t operatin g stat e and fau lts. The following a re
faults detected an d t ransmitted to th e ECM :
• Open circuit at one or severa l glow plu gs
• Short circu it in th e glow plug cir cuit
• Relay fau lt
If t he Glow plug relay detects a n open cir cuit at a
glow plug, it is st ored an d indica ted only once the
engine is running by t he preglow in dicator la mp com-
ing on for abou t one minut e a nd a fault is stored in
the ECM. If a short circu it, a glow plug ou tput stage
faulty or a tem per ature relat ed switching off of out-
pu t st ages is detected, th e fault is stored a nd indi-
cated im media tely by t he preglow indicator la mp
coming on. Once the fault is n o longer curr ent, th e
indicator is immediately switched off, bu t th e fau lt is
st ored in t he ECM. If the fault is constantly cu rrent,
the preglow indica tor la mp r emains on unt il the igni-
tion is switch ed off.
DIAGNOSIS AND TESTING - GLOW PLUG
RELA YS
Refer t o the a ppr opriate Diesel Powertr ain Dia gno-
sis Ma nual for informat ion on diagnosin g the glow
plug relays.
Fig. 1 GLOW PLUG (S)
1 - GLOW PLUG
2 - WIRING HARNESS CONNECTOR
3 - INTAKE MANIFOLD
4 - ENGINE COVER
8I - 2 IGNITION CONTROL VA
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