Circuit Description

Class 2 communications will not start until vehicle systems "on" power mode has been identified. Three discrete wires from ignition switch contacts are monitored by Instrument Panel Cluster (IPC) in order to determine present power mode (ignition switch position). See Fig 1 and Fig 2 . IPC communicates system power mode to all modules on class 2 data line.

DTC B1440 will set when IPC senses one of the 3 monitored ignition switch circuits has malfunctioned. When DTC B1440 sets, IPC implements default actions for each ignition switch position when faults are detected.

Both current and history DTC B1440 will clear after 100 consecutive ignition cycles if condition for setting DTC is no longer present. DTC will also clear when scan tool is used to clear DTCs.

Fig 1: Identifying Normal Power Modes

Courtesy of GENERAL MOTORS CORP.

Fig 2: Identifying Power Mode Code Setting Criteria

Courtesy of GENERAL MOTORS CORP.