DTC U1001-U1254: Loss Of XXX Communications: Description
Modules connected to class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among modules. When a module receives a message for a critical operating parameter, module records identification number of module which sent message for state of health messages monitoring. A critical operating parameter is one which, when not received, requires that module use a default value for that parameter. Once an identification number is learned by a module, it will monitor for that module's state of health message. Each module on class 2 serial data circuit which is powered and performing functions that require detection of a communications malfunction is required to send a state of health message every 2 seconds. When no message is detected from a learned identification number for 5 seconds, a DTC U1xxx, where xxx is equal to 3 digit identification number, is set.
Control module ID number list provides a method for determining which module is not communicating. A module with an internal class 2 serial data circuit malfunction or which loses power during current ignition cycle would have a lost communication DTC set by other modules. Modules that can communicate will set a DTC indicating module that cannot communicate. When no message is detected from a learned identification number for five seconds, a DTC U1xxx, where xxx is equal to 3 digit identification number, is set. See MODULE DTC IDENTIFICATION table.
| Module ID Number | Module Not Communicating |
|---|---|
| 016 | Powertrain Control Module |
| 040 | Electronic Brake Control Module/Electronic Brake Traction Control Module |
| 064 | Body Control Module |
| 088 | Inflatable Restraint Sensing & Diagnostic Module |
| 096 | Instrument Panel Cluster |
| 128 | Radio |
If more than one loss of communication DTC is set in either one or multiple modules, perform diagnosis in following order:
- Current DTCs before history DTCs, unless otherwise instructed in testing procedure.
- DTC which is reported most times.
- From lowest number DTC to highest number DTC.
DTC U1001-U1254 is set when, a message from a learned identification number has not been detected for past 5 seconds. Current DTCs U1001-U1254 will clear and become history DTCs when malfunction is no longer present. History DTCs U1001-U1254 will clear when module ignition cycle counter reaches reset threshold, without a repeat of malfunction.