1 CHT signal
2 CKP
3 PCM
4 Glow plug warning indicator
5 Sheathed-type glow plug relay (in CJB (Central Junction Box))
6 Parallel connected fuses (50 A each)
7 Sheathed-type glow plugs
Glow plug warning indicator
Note:
โข On vehicles without EOBD the glow plug warning indicator has a second function: If it flashes during driving then it is operating as a fault lamp, informing the driver there is a fault in the engine management system.
โข The glow plug warning indicator also serves as a fault lamp on vehicles with EOBD. However, in this case, it only indicates faults in the engine management system which are not significant for emissions.
โข The glow plug warning indicator is switched independently of the actual glow plug control. It does not therefore indicate anything about the glow plug status. It is therefore also not discernible from the glow plug warning indicator whether, for example, one or more glow plugs are not functioning.
Function
A glow plug control system is incorporated in the PCM. It is divided into two areas.
Preheating
The PCM receives the relevant temperature signal from the CHT sensor.
The length of the preheating period depends on the temperature signal (low temperature = longer preheating period).
The driver is informed of preheating by the lit glow plug warning indicator in the instrument cluster.
Post heating
Preheating is followed, after engine start, by the post heating phase.
Post heating helps to reduce engine noise, improve idling quality and reduce HC emissions through more efficient combustion just after start-up.
The post-heating phase is carried out up to an engine speed of approximately 2,500 rpm.
The post-heating phase is interrupted when engine speed exceeds 2,500 rpm. The service life of the glow plugs is increased as a result.
Effects of fault (engine cold)
longer starting process
loud combustion noise after starting
rough engine running,