Shift Light: Testing and Inspection

Fig. 068 - Wiring Diagram for Chart C-8B Manual Transmission Shift Light Check. VIN K:

CHART C-8B

MANUAL TRANSMISSION (M/T) SHIFT LIGHT CHECK

2.0L OHC (VIN K) "J" SERIES (TBI)

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:
a. Coolant temperature
b. Throttle position
c. Vehicle speed
d. Engine speed
The ECM uses the measured engine and vehicle speeds to calculate what gear the vehicle is in. It is this calculation which determines when the shift light should be turned "ON".

Fig. 067 Chart C-8B Manual Transmission Shift Light Check:

Test Description:
Numbers below refer to circled numbers on the diagnostic chart.
1. This should not turn "ON" the shift light. If the light is "ON", there is a short to ground in CKT 456 or a fault in the ECM.
2. When the diagnostic terminal is grounded, the ECM should ground CKT 456, and the shift light should be "ON".
3. This checks the shift light circuit up to the ECM connector. If the shift light lights, then the ECM connector is faulty, or the ECM does not have the ability to ground the circuit.