DTC U1001-U1254: Loss Of XXX Communications: Description

Serial data line is used to communicate information and commands between modules. When a module receives a message for a critical operating parameter (Node Alive message), a module records ID number of module which sent message for State Of Health (SOH) monitoring. Once an ID number is learned by a module, it will monitor for that module's Node Alive message. Each module on serial data line is required to send a Node Alive message every 2 seconds. When no message is detected from a learned ID number for 5 seconds, DTC U1XXX (XXX is equal to a 3-digit identification number) will set. See DTC SUFFIX IDENTIFICATION  table to determine which system is not communicating. For example, if DTC U1016 is set, Powertrain Control Module (PCM) is not communicating. A module with a class 2 serial data line malfunction or which loses power during a current ignition cycle will have a loss of communication DTC set by other modules that depend on information from that failed module. Modules that can communicate will set a DTC indicating a module cannot communicate.

A current DTC will clear when a Node Alive message from failed identification number is detected on class 2 serial data circuit, or at end of current ignition cycle. A history DTC will clear after 100 ignition switch cycles with no repeated malfunction.