DTC U0121-87: Lost Communication With Anti-Lock Brake System (ABS) Control Module: General Description

The Controller Area Network (CAN) High Speed Bus is used where data needs to be exchanged between modules at a high rate, to minimize the delay between the occurrence of a change in sensor value and the reception of this information by a control device using the information to adjust vehicle system performance. The CAN network consists of two twisted wires: one signal circuit is identified as CAN-High and the other signal circuit is identified as CAN-Low. At each end of the data bus there is a 120Ω termination resistor between the CAN-High and CAN-Low circuits. When the CANHigh signal circuit is driven higher, to about 3.5V, and the CAN-Low circuit is driven lower, to about 1.5V, the differential voltage becomes approximately 2.0 (+/- 0.5) V.