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

WARNING: This page is about a different car, the 2021 Kia Soul. However, it is still accessible from the selected car via links, so may be relevant.

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 CAN-high 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.