Firebird V8-305 5.0L VIN E TBI (1989)
Wiring Diagram For TCC
700-4R TRANSMISSION
CIRCUIT DESCRIPTION:
A fourth gear switch (mounted in the transmission) opens when the transmission shifts into fourth gear. This switch is used by the ECM to modify TCC
lock and unlock points, when in a 4-3 downshift maneuver.
TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.
1.
Unless the switch or circuit 446 is open, the "Scan" tool should display "NO," which indicates that the transmission is not in fourth gear. The
fourth gear switch should only be open in fourth gear.
2.
This step determines if the ECM and wiring are okay. Grounding circuit 446 should cause the "Scan" tool to display "NO," which indicates the
transmission is not in fourth gear.
3.
This checks the operation of the fourth gear switch. When the transmission shifts into fourth gear, the switch should open and the "Scan" tool
should display "YES."
4.
Disconnecting the TCC connector simulates an open switch to determine if circuit 446 is shorted to ground, or the problem is in the transmission.
DIAGNOSTIC AIDS:
A road test may be necessary to verify the customer complaint. If the "Scan" tool indicates that TCC is turning "ON" and "OFF" erratically, check the
state of the fourth gear switch to be sure it is not changing states under a steady throttle position. If the switch is changing states, check connections and
wire routing carefully. If the fourth gear switch is always open, the TCC may engage as soon as sufficient oil pressure is reached.