DTC U1255: Serial Data Line Malfunction: Testing
- Perform DATA LINK COMMUNICATIONS DIAGNOSTIC SYSTEM CHECK under SYSTEM TESTS. Go to next step.
- Turn ignition off. Install scan tool. Turn ignition on. Using scan tool, attempt to establish communication with other systems connected to data line (i.e., PCM, IPC, RFA). If scan tool communicates with other systems, go to next step. If scan tool does not communicate with other systems, go to DATA LINK COMMUNICATIONS DIAGNOSTIC SYSTEM CHECK under SYSTEM TESTS.
- Check serial data line for following intermittent conditions:
- Short to ground.
- Short to voltage.
- Check star connector No. 1 (ensure bus bar is properly inserted).
- Loose or damaged terminals.
If no problem is found, go to next step. If problem is found, repair as necessary. See appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS. After repairs, go to step 6 .
- Turn ignition off. Reinstall all components and connectors. Turn ignition on. Clear DTCs. Check for DTCs. If DTC U1255 is current, go to next step. If DTC U1255 is not current, system is operating properly.
- Replace BCM and program. See BODY CONTROL MODULE (BCM) under REMOVAL & INSTALLATION. See BCM PROGRAMMING/RPO CONFIGURATION under PROGRAMMING. After repairs, go to next step.
- Turn ignition off. Reinstall all components and connectors. Turn ignition on. Clear DTCs. Perform DATA LINK COMMUNICATIONS DIAGNOSTIC SYSTEM CHECK under SYSTEM TESTS.