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Component Location

General Description

Heating combustion chamber, glow plug increases fuel ignitibility and makes fuel in the foggy state easily when engine is cold. Thus, glow plug makes engine starting easily and decreases exhaust gas produced just after turning engine on when engine is cold.

Glow plug control unit(GCU) controls operation of glow plug by PWM with ECTS signal, battery voltage and IG KEY ON signal.

Through glow lamp in cluster, ECM let drivers know if glow plug is ON.

DTC Description

DTC P0684 is set when feedback signal is not normal for 1 sec.

DTC Detecting Condition

Item	Detecting Condition			Possible Cause
DTC Strategy	• Voltage monitoring			• Glow plug / control unit circuit error • Faulty GCU
Enable Conditions	• IG key ON
Threshold value	• Feedback signal is not normal
Diagnosis Time	• 1 sec.
Fail Safe	Fuel cut	NO	• -
	EGR Off	NO
	Fuel Limit	NO
	Check Lamp	OFF

Diagnostic Circuit Diagram

note

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Signal Waveform & Data

Fig 1) Glow plug is controlled to duty 28% when IG key turns to ON from OFF and cold engine.

Fig 2) Glow plug control signal waveform when IG key turns to ON from OFF and warmed engine.