SCC(Smart Cruise Control) has additional function which helps to keep safety distance from the car ahead as compared with conventional ACC(Auto Cruise Control). SCC uses CAN communition to exchange information, which is required for control, with related ECUs and to receive input signal from SCC remote control switch and to transmit output signal to cluster. CAN communication type is communication speed is high speed CAN and two terminal resistance (120O) is connectted in a line. SCC has a CAN controller to control signal exchange.
SCC sets this code when the messages(EMS6) from ECM was not received within the last 500msec or improper message, checksum detected. System recovers to normal state if the message is received again.
Item
Detecting Condition
Possible cause
DTC Strategy
CAN message monitoring
Open or poor connection in between ECM and SCC
Faulty ECM
Enable Conditions
Engine Run (engine rpm higher than 400 at least for 2s)
Threshold value
The messages(EMS6) from ECM was not received within the last 500msec
Improper messages(EMS6) detected
Improper checksum detected
Diagnosis Time
500ms
Recover Condition
As soon as the message is received again
Fail Safe
VSM2 Red warning lamp turns on, VSM2 function permanently not available
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 occurence 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.