DTC U1001-U1254: Loss Of Communication With XXX: Description

Modules connected along class 2 serial data line monitor serial data communications during normal vehicle operation. Operating information and commands are exchanged between modules and operating systems. When a module receives a message from another system, that module records identification number of system which sent State Of Health (SOH) message. If SOH is not received, receiving module must use a default value for non-transmitting identification number. Once an identification number is learned by a module, it will monitor that system for its unique SOH message. Each system on the class 2 serial data line must send a SOH message every two seconds. When no message is detected from any system for five seconds, DTC U1XXX (XXX is equal to the three digit identification number) will set. See DTC ID NUMBER  table to determine which system is not communicating. For example, if DTC U1016 is set, Powertrain Control Module (PCM) is not communicating.

Current DTC will clear when SOH message from the failed identification number is detected on class 2 serial data line or at the end of the current ignition cycle. History DTC can only be cleared using scan tool or Driver's Information Center (DIC).