On a CAN bus with 120 Ω termination resistors at both ends, the resistance between CAN_H and CAN_L was measured with the power off. Which value is closest to that of a normal bus?

Answer: C. 60 Ω

A CAN bus has a 120 Ω termination resistor at each end to prevent signal reflections. Seen from between CAN_H and CAN_L, the two 120 Ω resistors are in parallel, giving 120 × 120 / (120 + 120) = 60 Ω. A reading of 120 Ω suggests one termination resistor is missing, and around 40 Ω suggests a wiring error such as three termination resistors being fitted. 240 Ω is the mistake of treating the two as being in series.