DTC U1128: Loss Of Serial Communications - IRC: Notes
NOTE:
To identify wire colors and components on class 2 serial data line, see DATA LINK CONNECTOR in WIRING DIAGRAMS
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Every 2 seconds while ignition switch is in RUN position, control modules that communicate on class 2 data bus transmit a performance condition signal to indicate system is operating properly. Signal is then transmitted to BCM.
DTC U1128 will set when voltage to Internal Radio Controller (IRC) is in normal operating range (9-16 volts), DTCs U1300 and U1301 are not current, and BCM does not receive signal from IRC for five seconds. DTC U1128 will clear when IRC transmits signal to BCM (current DTC) or when scan tool is used (history DTC).