DTC P1A72 Chevrolet

Description

Key on or engine running; and a module detected that it could not communicate with the VTD controller for 1 second. Modules connected to the Class 2 circuit monitor for data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the identification number of the module that sent the message for State of Health monitoring (Node Alive messages). Once a module learns an identification number, it will monitor for that modules Node Alive message. Each module on the Class 2 circuit that is powered and performing functions that require detection of a communications malfunction is required to send a Node Alive message every two seconds. When no message is detected from a learned identification number for five seconds, a DTC U1xxx (the Xs identify the 3-digit identification number) is set.