LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Buick >> 1991 >> Reatta 2D Convertible >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - Pcm/BCM >> Self-Diagnostic System Check >> Chart D-1, Grounded Serial Data Circuit
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Chart D-1, Grounded Serial Data Circuit

With grounded serial data circuit, BCM will not be able to communicate with any other devices in system. Voltage measured anywhere in circuit will zero. IPC will display ELECTRICAL PROBLEM; ECCP will display dashes ("---").

NOTE: Test numbers refer to numbers on diagnostic chart.
  1. This step splits the system in half to help isolate source of grounded serial data line. If taking IPC out of the system allows both halves of serial data line to rise more than one volt, source of short has been located. The remaining steps follow same pattern in that components are removed from serial data line until normal voltage range is again measured. When section of circuit is isolated, a simple check of wire for short to ground will differentiate between grounded wire or ground in a device remote.
Fig 1: Chart D-1, Schematic, Grounded Serial Data Circuit
G91G07764
Fig 2: Flow Chart D-1, Grounded Serial Data Circuit (1 of 2)
GB0022600
Fig 3: Flow Chart D-1, Grounded Serial Data Circuit (2 of 2)
GB0022601