Fiero V6-173 2.8L (1986)
Wiring Diagram for Chart C-8 - Manual Transmission Shift Light Check
CHART C-8 - MANUAL TRANSMISSION (M/T) SHIFT LIGHT CHECK
Circuit Description:
The shift light indicates the best transmission shift point for maximum fuel economy. The light is controlled by the ECM and is turned "ON" by
grounding CKT 456.
The ECM uses information from the following inputs to control the shift light:
^
Coolant temperature
^
TPS
^
VSS
^
RPM
The ECM uses the measured rpm and the vehicle speed to calculate what gear the vehicle is in. It's this calculation that determines when the shift
light should be turned "ON."
Test Description:
Numbers below refer to circled numbers on the diagnostic chart.
1.
This should not"ON" the shift light. If the light is "ON," there is a short to ground in CKT 456 wiring or a fault in the ECM.
2.
When the diagnostic terminal is grounded, the ECM should ground CKT 456 and the shift light should come "ON.
3.
This checks the shift light circuit up to the ECM connector. If the shift light illuminates, then the ECM connector is faulty or the ECM does not have
the ability to ground the circuit.
