Component Location
General Description
Preheating on Diesel engine improves cold starting with glow plug which heat combustion chamber. Preheating before starting improves cold starting, preheating after starting reduces to generate white smog. GCU(Glow plug Control Unit) is installed on the upper side of timing chain cover and is operated by 12V power supply. GCU receives sensors data such as 1)engine coolant temperature, 2)engine rpm, 3)fuel injection amount from ECM via CAN communication in order to control glow plug. GCU controls 1)glow plug operation with PWM, 2)compensates voltage when low voltage 3)controls not to flow over current on glow plug 4) retrieves DTC after diagnosing each glow plug corresponding to engine condition.
ISS(Instant Starting System) operated by 4.4Valtage, which is slim and enhanced heating performance, is newly adopted on S engine. GCU emerges battery voltage to glow plug directly for 1~ 2sec. at IG key ON. After that, GCU controls glow plug operating voltage with PWM corresponding to Engine condition. ISS glow plug is increased to 1000? within 2 ~3sec. so that starting performance is reached as same level as gasoline. In addition, it is realized that consumption of electricity is optimized by PWM control.
DTC Description
DTC P0683 is set when communication between ECM and GCU is error at IG key "ON" because of CAN message error. It is caused by terminal corrosion /contamination / poor connection or faulty GCU.
DTC Detecting Condition
Item | Detecting Condition | Possible Cause |
DTC Strategy | ? Voltage monitoring | ? CAN communication circuit (ECM ? GCU) ? Faulty GCU |
Enable Conditions | ? IG key ON |
Threshold Value | ? GCU CAN communication message error. |
Diagnostic Time | ? 0.6 sec. |
Fail Safe | Fuel cut | NO | |
EGR Off | NO |
Fuel Limit | NO |
Check Lamp | OFF |
Specification
Communication Format | Digital "0" | Digital "1"( BUS idle ) | Resistance on CAN communication |
High | Low | High | Low | Inside of ECM | Junction box in compartment |
CAN 2.0B | 3.5V | 1.5V | 2.5V | 2.5V | 120? (20?) | 120? (20?) |
Diagnostic Circuit
Signal Waveform
Monitoring CAN HIGH and LOW simultaneously is important in monitoring CAN communication waveform. When CAN HIGH signal rise to 3.5V and LOW signal drops to 1.5V - voltage difference between HIGH and LOW signal is 2V - at BUS IDLE state(DIGITAL "1") whose reference voltage is 2.5V, "0" is recognized. Besides, comparing HIGH and LOW signal if opposite waveform is detected with the reference voltage of 2.5V, Check if current cam signal transfers correctly.
Continuous "0"signal above 6BIT means the occurrence of error in CAN communication. 1BIT is easily distinguished as calculating the time when "SOF"(START OF FRAME) which notifies the start of frame occurs. Check if "0"signal above 6BIT is detected continuously when monitoring CAN communication waveform.