Circuit/System Description

WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.

The devices connected to the Powertrain CAN serial data circuits (4054 & 4055) monitor for serial data communications during normal vehicle operation. The serial data is transmitted on two twisted wires that allow speeds up to 2 Mbit/s. The twisted pair is terminated with two 120 Ω resistors, one is internal to the K20 Engine Control Module (ECM) and the other can be a separate resistor in a connector assembly or in another device. The resistors are used as the load for the Powertrain CAN bus during normal vehicle operation. The Powertrain CAN bus is a differential bus. The Powertrain CAN serial data (+) and Powertrain CAN serial data (-) circuits are driven to opposite extremes from a rest or idle level of approximately 2.5 V. Driving the lines to their extremes, adds 1 V to the Powertrain CAN serial data (+) circuit and subtracts 1 V from the Powertrain CAN serial data (-) circuit. If serial data is lost, devices will set a no communication code against the non-communicating device. Note that a loss of serial data DTC does not represent a failure of the device that set it.