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Home >> Cadillac >> 1998 >> Seville STS >> Repair and Diagnosis >> Body & Frame >> Body, Cab Control Systems >> Body Control Module >> Diagnosis & Testing >> DTC U1128: Loss Of Communications With IRC >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform entertainment system diagnostic system check. After performing system check, go to next step.
  2. Using scan tool, attempt to establish communications with radio/IRC. If scan tool communicates with IRC, go to next step. If scan tool does not communicate with IRC, diagnose radio/entertainment system.
  3. Check and repair Class-II serial data line circuit No. 1807 (Purple wire) for intermittent conditions. See WIRING DIAGRAMS  . After repairs, go to next step.
  4. Turn ignition off. Reconnect components and connectors. Turn ignition on. Clear DTCs using scan tool. After clearing DTCs, check system operation.
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