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). Control step is as follows.
1. Radar sensor measures distance from the car ahead and relative speed (Radar Sensor)
2. SCC calculates acceleration/deceleration value for keeping relevant distance from the car ahead according to speed and transmits this value to ESP system.
3. ESP performs engine torque and brake control after calculating torque for making received acceleration/deceleration value.
SCC sets this code in case of as follow.
1. Time out of SCC message
2. Inconsistency in data
3. Failure in alive counter
4. ESP can not perform SCC control because it has a fault
? The DTCs, C1636/C1637, can happen with C1638 at the same time.
Item
Detecting Condition
Possible cause
DTC Strategy
CAN message monitoring
Faulty SCC
ESP system error
Open in harnesses between SCC and ESP
Enable Conditions
Engine Run (engine rpm higher than 400 at least for 2s)
Threshold value
SCC receives a message which indicates SCC communication failure from ESP ECU
Diagnosis Time
100ms
Recover Condition
As soon as the signal is alright again
Fail Safe
Red SCC warning lamp turns on
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.