Battery voltage is supplied to the OnStar® Communication Interface Module (CIM) by circuit 1340. This input is internally monitored by the CIM for proper operating voltage. The minimum voltage for proper operation is 9.0 volts, if circuit 1340 drops below 9.0 volts, this DTC will fail. DTC B1327 will remain current until system voltage is above 9.5 volts for 1.2 seconds. Under 8.5 volts, communication with OnStar® system using scan tool will be disabled.

Check for poor connections at the CIM and instrument panel fuse block. Inspect harness for backed out terminals, improper terminal mating, broken connector locks, improperly formed or damaged terminals and poor terminal-to-wire connections (terminal crimped over insulation).

If fault is suspected to be intermittent, moving harness wiring may help in locating fault.