DTC U1255: Serial Data Line Malfunction: Testing

If IPC diagnostic system check was performed, go to next step. If IPC diagnostic system check was not performed, go to procedures in IPC DIAGNOSTIC SYSTEM CHECK .
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, BCM, RFA) If scan tool communicates with other systems, go to next step. If scan tool does not communicate with other systems, locate and repair problem in data link connector system. See WIRING DIAGRAMS .
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. 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 IPC. See INSTRUMENT PANEL CLUSTER under REMOVAL & INSTALLATION. Go to next step.
Turn ignition off. Reinstall all components and reconnect all connectors. Turn ignition on. Clear DTCs. Perform procedures in IPC DIAGNOSTIC SYSTEM CHECK .