1-4 Shift

The 1 to 4 shift indicator is externally controlled by the Powertrain Control Module (PCM). The 1 to 4 shift indicator is used on 6 speed manual transmission vehicles for fuel economy reasons. The Instrument Panel Cluster (IPC) illuminates this indicator when the PCM determines that a 1 to 4 sift is necessary. The IPC provides power and the PCM provides the ground for illumination.