Chart C-8B, Shift Light Check: Notes
The shift light indicates optimum shift point, for manual transmission vehicles, to achieve best fuel economy. Light comes on when ECM provides ground for circuit No. 456.
The ECM uses information from coolant temperature sensor, TPS, VSS and engine RPM to determine when to activate shift light.
NOTE:
Test numbers refer to test numbers on diagnostic chart. This chart should only be used if a problem is present with shift light.