Chart C8B - Man. Trans. Shift Light (5.0/5.7L)
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 circuit No. 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. This calculation determines when the shift light should be turned on.
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- This test should not turn on the shift light. If the light is on, there is a short to ground in circuit No. 456 wiring or a fault in the ECM.
- When the diagnostic terminal is grounded, the ECM should ground circuit No. 456 and the shift light should come on.
- 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.