Automotive Ethernet (100BASE-T1 or 1000BASE-T1) employs differential signaling to reduce electromagnetic interference. CHEPQ diagnostic tools measure voltage noise amplitude and frequency on both lines, identifying excessive common-mode or differential-mode noise sources. High noise levels can stem from poor shielding, ground loops, or faulty connectors, causing packet loss or degraded communication in advanced systems like ADAS or infotainment. Understanding noise characteristics allows targeted EMI mitigation strategies, preserving real-time data exchange essential for vehicle safety.