Lumina V6-204 3.4L DOHC (1991)
Shift Light: Testing and Inspection
Chart C-8
Chart C-8 Wiring Diagram
CIRCUIT DESCRIPTION:
The shift light indicates the best point for maximum fuel economy. The light is controlled by the ECM and is turned "ON" by grounding circuit 456. The
ECM uses information from the following inputs to control the shift light:
^
Coolant temperature must be above 16~C (61~F)
^
TPS above 4%
^
VSS
^
RPM above about 1900
^
Air flow - The ECM uses rpm VSS and airflow to calculate what gear the vehicle is in. It's this calculation that determines when the shift
light should be "ON." The shift light will stay "ON" 5 seconds after the conditions were met to turn it "ON."
TEST DESCRIPTION:Numbers below refer to circled numbers on the diagnostic chart.
