Circuit/System Description

For an overview of the component/system, refer to:Transfer Case Description and Operation

The ECM uses the following to determine the transfer case mode.

1. Compares the transmission output speed (Transmission OSS) to the vehicle speed (Vehicle Speed Sensor) to calculate transfer case range/ratio.
2. LAN message sent by the transfer case shift control module to the ECM indicating transfer case range.

The ECM uses the transfer case range to determine engine torque required and transmission shift schedule.

The internal fault detection is handled inside the control module. No external circuit diagnosis is involved.