1988 PONTIAC FIERO Service Repair Manual

6E2-C7-6 DRIVEABILITY AND EMISSIONS - 5.OL (VIN E)
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DRIVEABILITY AND EMISSIONS - 5.0L (VIM E) 6E2-C8-1
SECTION C8
"FRANSMISSIBN CONVERnEW CLUTCH (TCC) SYSTEM
CONTENTS
GENERAL DESCRIPTION ............... C8-1 RESULTS OF INCORRECT TCC
PURPOSE
........................ C8-1 OPERATION ..................... C8-2
......................... OPERATION ...................... C8-1 DIAGNOSIS CS-2
.................... CIRCUIT DESCRIPTION ....e.e..eea..e C8-1 ON-CAR SERVICE C8-2
................. PARTS INFORMATION 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.
OPERATION
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 require-
ments are met. See Section
"7A".
Before the ECM activates the TCC apply solenoid,
several inputs must be monitored:
e 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.
@ 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.
CIRCUIT DESCRIPTION
When the brake pedal is not depressed (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.
Figure C8-1 - TCC Solenoid
Some transmission use other internal switches in
addition to the TCC solenoid.
@ 700-R4. transmissions normally use a 4th gear
switch to send
a signal to the ECM telling it
when the transmission is in
4th gear. The
ECM uses this information to vary the
conditions under which the clutch applies or
releases. However, the transmission does not
have to be in
4th gear in order for the ECM to
turn the clutch
"ON"
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.

6Ef-C8-2 BRlVEABlLlYV AND EMISSIONS - 5.OL (VIN E) ----
RESULTS OF INCORRECTTCC OPERATION
An engine stall will result if the converter clutch
remains applied at all times.
If the converter clutch does not apply, fuel
economy may be lower than expected.
The transmission converter clutch
(TCC) system
has different operating characteristics than an
automatic transmission without TCC.
If the driver
complains of a "chuggle" or "surge" condition, the car
should be road tested and compared to a similar car to
see if a real problem exists. Another TCC complaint
may be
a downshift felt when going up a grade,
especially with cruise control. This may not be
a
downshift, but a clutch disengagement due to the
change in TPS to maintain cruising speed. The
Owner's Manual section on TCC operation should be
reviewed with the driver.
DIAGNOSIS
The diagnosis of the TCC system is covered in
ClIART C-8. If the ECM detects a problem in the VSS
system, a Code
24 should set. In this case see Code 24
Chart.
If the ECM doesn't switch the TCC "ON" when
driving, but will turn it
"ON" when the "test"
terminal is grounded with ignition "ON" and engine
stopped, the sensors such as coolant, speed, and
throttle position should be checked.
ON-CAW SERVICE
@ See Section "7" for TCC Solenoid.
@ See Section "SH" for VSS (HP mounted) and brake
system.
PAR- SNFORMATBIQN
PART NAME GRQUQ
.......................... Sensor, VSS 9.761
........................ Solenoid, TCC 4.122

DRIVEABILITY AND EMiSS88NS - 5.0% (VIN E) 6E2-C8-3

6EZ-C8-4 DRIVEABILITY AND EMISSIONS - 5.OL (VIN E)
I5 WAY (FRONT VIEW)
SPEED INPUT
4rH GEAR SIGNAL
422 TANIBLK
ALDL CONNECTOR
CHART C-8A
TRANSMISSION CONVERTER CLUTCH (TCC)
ELECTRICAL DIAGNOSIS
(Page 1 of 2)
5.OL (VIN E) "F" "SERIES (TBI)
Circuit Description:
The purpose of the automatic transmission torque converter clutch is to eliminate the power loss of the
torque converter, when the vehicle is in a cruise condition. This allows the convenience of the automatic
transmission and the fuel economy of a manual transmission.
Fused battery ignition is supplied to the TCC solenoid through the brake switch. the ECM will engage
TCC
by grounding CKT 422 to energize the solenoid.
TCC will engage when:
- Vehicle speed above 24 mph - Engine at normal operating temperature (above 70°C, 156°F)
- Throttle position sensor output not changing, indicating a steady road speed
- Brake switch closed
Test Description: Numbers below refer to circled solenoids
and relays before installing a
numbers on the diagnostic chart. replacement ECM. Replace
any solenoid or relay
1. Confirms 12 volt supply as well as continuity of that
measures less than 20 ohms.
TCC circuit.
2. Grounding the diagnostic terminal with engine Diagnostic Aids:
"OFF", should energize the capability of the ECM An
engine coolant thermostat that is stuck open or
to control the solenoid. opens
at too low a temperature, may result in an
3. Solenoid coil resistance must measure more than inoperative TCC.
20 ohms. Less resistance will cause early failure
of the ECM
drive^.". Using an ohmmeter, check
the solenoid coil resistance of
all ECM controlled

DRIVEABILITY AND EMISSIONS - 5.8L (VIN E) 6EZ-C8-5
TRANSMlSSlON CONVERTER CLUTCI-I (KC)
@ GROUND DIAGNOSTIC 22 SHORTED TO
I EQUIPPED WITH I I THE CORRECT o WITH TEST LIGHT I PROM. TO CHECK I CONNECTED I 4TCI GEAR SWITCH I I (700-R4ONLY),SEE I CHART C-8 (2 OF 2). 1 L ------------ A

6E2-C8-6 DRIVEABILITY AND EMISSIONS - 5.OL (VIN E)
I.P. HARNESS CONNECTOR 15 WAY (FRONT VIEW)
ECM
VEHICLE SPEED SIGNAL
SPEED INPUT
4TH GEAR SIGNAL
422 TANIBLK
ALDL CONNECTOR
* 85 4435-66 6-8-87
CHART C-8A
700-4R TRANSMISSION
ELECTRICAL DIAGNOSIS
(Page 2 of 2)
5.0L (VIN E) "F" "SERIES (TBI)
Circuit Description:
A 4th gear switch (mounted in the trans.) opens when the trans. 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.
1. Unless the switch or CKT 446 is open the "Scan"
should display "NO", indicating the trans. is not
in 4th gear.
The 4th gear switch should only he
open whiie in 4th gear.
2. 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.
3. Checks the operation of the 4th gear switch.
When the trans. shifts into 4th
geir the switch
should open and the "Scan" should display
"YES".
4. Disconnecting the TCC connector simulates an
open switch to determine if CKT
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" indicates TCC is
turning
"ON" and "OFF" erratically, check the state
of the 4th gear switch to he sure it is not changing
states under a steady throttle position.
If the switch is
changing states, check connections and wire routing
carefully. Also if the 4th gear switch is always open
the
TCC may engage as soon as sufficient oil pressure
is reached.

DRIVEABILITY AND EMISSIONS - 5.OL (VIN E) 6EZ-C8-7
DISCONNECT TCC ELECTRICAL CONNECTOR.
SHIFT VEHICLE INTO OVERDRIVE