Circuit/System Description

The serial data circuit is the means by which the control modules in the vehicle communicate with each other. When the vehicle is ON, each control module communicating on the serial data circuit sends a state of health (SOH) message to ensure that the control module is operating properly. When hybrid powertrain control module 2 stops communicating on the serial data circuit, for example if the hybrid powertrain control module 2 loses power or ground, the SOH message it normally sends on the serial data circuit disappears. Other control modules on the serial data circuit, which expect to receive that SOH message, detect its absence; those control modules in turn set a DTC associated with the loss of SOH of the hybrid powertrain control module 2. A loss of serial data communications DTC does not represent a failure of the control modules that contain the stored code.