Chart B2: BCM-To-IPC Communication Problem

You are at this chart because odometer, with key on, read all zeroes and courtesy lights turned on when switch was actuated. These symptoms indicate a loss of BCM data communication to Instrument Panel Cluster (IPC), which can be caused by several different problems.

Test Number 1)  If ALDL connector cover is off or loose, this could cause a break in data circuit, cutting off BCM communication to IPC under certain electrical conditions. Should this be the case, securely connect ALDL cover and return to beginning of SELF-DIAGNOSTIC SYSTEM CHECK.

Test Number 2)  This step isolates ALDL connector, the ECM and programmer from data circuit in order to find fault. If odometer reads actual accumulated miles, the fault lies within network between ALDL connector, the ECM and programmer.

Test Number 3)  This checks to see if fault is due to ECM and its related data circuits, or the programmer and its related circuits.

Test Number 4)  This determines if fault is associated with IPC or BCM.

Test Number 5)  This determines if fault is due to programmer or ground circuit No. 801 from Central Power Supply (CPS).

Test Number 6)  This step determines if fault is in the last section of 800 circuit or the IPC. Jumper around the IPC to isolate the last section of 800 circuit and connect it with a known good circuit.