Pontiac Fiero 1988 Service Manual page 703

6E3-C8-6 DRIVEABILITY AND EMISSIONS - FUEL INJECTION (PORT)
IGN 1
3 9 PNK/BLK
GAGES ! SHIFT LIGHT
INSTRUMENT
PANEL
p
456 TAN/BLK
I. P.
CONNECTOR
A 7
SHIFT LIGHT
CONTROL DRIVER
5-26-87
5-8-87
* 5 S 1 3 3 9 - 6 E
CHAIT C-8B
MANUAL TRANSMISSION (M/T) SHIFT LIGHT CHECK
2 . 8 L f f P f f SERIES (PORT)
Circuit Description:
The shift light indicates the best transmission shift point for maximum fuel economy. The light is controlled
by the electronic control module (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 turn "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.