Pontiac Fiero 1988 Service Manual page 562

D R I V E A B I L I T Y A N D E M I S S I O N S - F U E L I N J E C T I O N ( T B I ) 6 E 2 - C 8 - 1
S E C T I O N C8
TRANSMISSION CONVERTER CLUTCH (TCC) SYSTEM
CONTENTS
GENERAL DESCRIPTION .
PURPOSE
O P E R A T I O N
CIRCUIT DESCRIPTION
DIAGNOSIS . . ,
ON-CAR SERVICE . . . . . .
C8-1
C8-1
C8-1
C8-1
C8-1
C8-2
GENERAL DESCRIPTION
PURPOSE
The transmission converter clutch (TCC) system
is designed to eliminate power loss by the converter
(slippage) thus increasing fuel economy. By locking
the converter clutch, a more effective coupling to the
flywheel is achieved. The converter clutch is operated
by an ECM controlled solenoid.
O P E R A T I O N
Engagement of the TCC is accomplished by a
solenoid operated valve within the transmission. The
solenoid is activated when an internal switch in the
ECM is grounded. Although the ECM may command
the TCC "ON", the converter clutch will not apply
until internal transmission fluid pressure
requirements are met. See Section "7A".
Before the ECM activates the TCC apply solenoid,
several inputs must be monitored:
• Vehicle Speed - Must be above a certain value
before the TCC can be applied.
• Coolant Temperature - The engine coolant
temperature must be above a certain value
before the TCC can be applied.
c Throttle Position Sensor - After the TCC is
applied, during low engine load condition, the
ECM uses the information from the TPS to
release the clutch when the car is accelerating
or decelerating at a certain rate.
C I R C U I T D E S C R I P T I O N
The 12 volt power supply for the solenoid in the
transmission is provided through a normally closed
switch located on the brake pedal linkage. When the
brake pedal is depressed (switch open) the power
supply to the TCC solenoid is interrupted and the TCC
is disengaged regardless of any other conditions. A 3
rd
gear apply switch (closed in 3
r d
gear ) is placed in
series between the brake switch and the TCC solenoid.
This switch will prevent TCC engagement until
the transmission is in 3
rd
gear.
SHIFT LIGHT
DESCRIPTION . . .
DIAGNOSIS
ON-CAR SERVICE
PARTS INFORMATION
• • • • <
© o © o © © © ,
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C8-2
CB-2
C8~2
C8-2
C8-2
HI
TCC SOLENOID
(T]
CHECK BALL SEAT
m CHECK BALL
4S 0548-6E
Figure C8-1 - TCC Solenoid
When the brake pedal is not depressed (switch
closed) and the transmission is in 3
r d
gear (3
rd
gear
switch closed), battery voltage will be fed to the TCC
solenoid. If the ECM has determined that conditions
are correct, the circuit from the TCC solenoid will be
completed to ground through the ECM and the TCC
solenoid will be activated.
DIAGNOSIS
The diagnosis of the TCC system is covered in
CHART C-8. If the ECM detects a VSS input problem
in the system, a Code 24 should set. In this case, see
Code 24 chart.
If the ECM doesn't switch the TCC "ON" when it
should, but the TCC will turn "ON" when the "test"
terminal is grounded with ignition "ON" and engine
stopped, sensors such as coolant, speed, and throttle
position should be checked.