General Information

Smart Cruise Control
C1638 ACC communication error - General Information

Component Location





General Description

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 ESC system.
3. ESC performs engine torque and brake control after calculating torque for making received acceleration/deceleration value.

DTC Description

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. ESC can not perform SCC control because it has a fault
** The DTCs, C1636/C1637, can happen with C1638 at the same time.

DTC Detecting Condition





Diagnostic Circuit Diagram










Signal Waveform & Data




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.