Firebird V8-305 5.0L VIN F FI (1987)
Chart C-8A Torque Converter Clutch
CHART C-8A TORQUE CONVERTER CLUTCH (TCC) DIAGNOSIS
Circuit Description:
A 4th gear switch (mounted in the transmision) opens when the transmission shifts into 4th gear, and this switch is used by the ECM to modify TCC lock
and unlock points, when in a 4-3 downshift maneuver.
Test Description: Numbers below refer to circled numbers on the diagnostic chart.
3.
Unless the switch or CKT 446 is open "Scan" should display "NO," indicating the trans. is not in 4th gear. The 4th gear switch should only be
open while in 4th gear.
4.
This step determines if the ECM and wiring are OK. Grounding CKT 446 should cause the "Scan" to display "NO," indicating the trans. is not in
4th gear.
5.
Checks the operation of the 4th gear switch. When the trans. shifts into 4th gear the switch should open and the "Scan" should display "YES."
6.
Disconnecting the TCC connector simulates an open switch to determine if CKT 446 is shorted to ground or the problem is in the transmission.
