Chart B, Odometer Displays Error (LOS Of Serial Data) (REATTA & Riviera)

Fig 1: Chart B - Wiring Schematic (Reatta & Riviera)

Courtesy of GENERAL MOTORS CORP.

IPC indicates loss of serial data communication by displaying ERROR in odometer and illuminating ELECTRICAL PROBLEM telltale light. Loss of serial data communications can occur for the following reasons:

• Short to ground somewhere in circuit No. 800
• Short to voltage somewhere in circuit No. 800
• Two opens in circuit No. 800
• Internal fault in BCM or IPC
• Open in ECCP ground circuit
  NOTE: Test numbers refer to numbers on diagnostic chart.
  1. This steps checks if BCM is awake and functioning. If it is not, use chart B-1 to isolate fault.
  2. This step checks if ECC head has lost data communication along with IPC.
  3. Code B556 indicates IPC EEPROM error. Odometer will display ERROR, but diagnostics will be accessible.
  4. Since IPC lost data communications, creating an open in data line at ALDL connector should remove data communications from ECCP as well. If not, IPC is receiving data but is unable to communicate due to poor connection or internal problem.
  5. This test indicates data line shorted to ground.
  6. This test indicates data line functioning properly, but with multiple opens isolating IPC and ECCP from BCM.
  7. This test indicates data line shorted to voltage.

Fig 2: Chart B - Troubleshooting Diagram (Reatta & Riviera)

Courtesy of GENERAL MOTORS CORP.