Shift Light: Description and Operation

Purpose:
Most manual transmission vehicles under 8500 GVW have a shift light on the instrument panel.
The shift light is commonly used to achieve improved fuel economy, by prompting the driver when to upshift. Depending on the engine/transmission installed in the vehicle, the shift light can have the following characteristics:
- Indicates proper shift point for maximum fuel economy.
- Indicates engine over-speed.
- Shift light is inoperative.

Operation:
The light is controlled by the control module and is turned "ON" by grounding CKT 456.
The chart details normal shift light operation: