1988 PONTIAC FIERO Service Repair Manual

6E3-C7-8 2.8L (VIM 9) DRIVEABILITY AND EMISSIONS
BLANK

DRIVEABILITY AND EMlSSlONS 2.8L (VIN %I 6E3-C8-1
TRANSMISSION CONVERTER CLUTCH (KC) SYSTEM
AND MANUAL
TRANSMISSION SHIFT LIGHT
CONTENTS
GENERAL DESCRIPTION ................ C8-1 DIAGNOSIS ..........ee...ee....e.e. C8-1
PURPOSE ......................... C8-1 SHIFT LIGHT (MIT) DESCRIPTION ........ C8-1
OPERATION ....................... C8-1 DIAGNOSIS ....................... .. C8-1
ON-CAR SERVICE ...................*. C8-1
GENERAL DESCRIPTION
PURPOSE
The transmission converter clutch (TCC) svstem
uses a solenoid operated valve in the automatic
transmission to couple the engine flywheel to the
output shaft of the transmission thru the torque
converter. This reduces the slippage losses in the
converter, which increases fuel economy.
OPERATION
For the converter clutch to apply, two conditions
must be met:
o Internal transmission fluid pressure must be
correct. For information on internal transmission
operation, see Section
"7A". This section will cover
only the electrical operation of the TCC system.
@ The ECM grounds a switch internally to turn on a
solenoid in the transmission. This moves a check
ball, which will allow the converter clutch to
apply, if the hydraulic pressure is correct, as
described above.
The ECM controls the TCC apply solenoid by
looking at several sensors:
@ Speedo Buffer Sensor (also called vehicle speed
sensor
(VSS). Speed must be above a certain value
before the clutch can apply.
@ Coolant Temperature Sensor. Engine must be
warmed up before clutch can apply about
65OC
(149°F').
Throttle position sensor ('I'PS). After the
converter clutch applies, the
HCM uses the
information from the TPS to release thc clutch
when the car is accelerating or decelerating at a
certain rate.
@ 'I'he brake switch is also part of the 'I'CC circuit as
it will remove battery voltage to the 'KC solenoid
when the brake pedal is depressed.
@ Gear Select Switch. The 4th gear switch is used 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.
IIowever, the
transmission does not have to be in fourth gear in
order for the ECM to turn the clutch on.
If the converter clutch is applied at all times. the
engine will stall immediately, just as in
u manual
transmission with the clutch applied.
If the converter clutch does not apply, fuel
ecomony
may be lower than expected. If the vehicle
speed sensor fails, the TCC will not apply. If the 4th
gear switch does not operate, the TCC may not apply
at the right time.
DIAGNOSIS
The diagnosis of the TCC system is covered in
CHART C-8
. If the ECM detects a problem in the
system,
a Code 24 should set. In this case see Code 24
CHART.
SHIFT LIGHT (MiT) DESCRIPTION
'The purpose of the shift light is to provide a
display which indicates the optimum fuel economy
point for up
shifling the manual transmission based
on engine speed
and load. 'I'he display is a lamp on the
instrument panel. Activation of the ECM driver turns
the lamp
on.
'I'he shift light circuit can he checlted using
CHAR?' C-8C.
ON-CAR SERVICE
@ See Section "8B" if the shift light bulb needs
replacement.
@ See Section "6E" to repair wiring problem.
@ See Section "6C" if ECM is to be replaced.

6E3-C8-2 2.8L (VIN S) DRIVEABILITY AND EMISSIONS
VEHICLE SPEED SIGNAL
SPEED INPUT
CONNECTOR
aTH GEAR SIGNAL
422 TAN/BLK
4TH GEAR SW.
TRANSMISSION
ALDL CONNECTOR
TCC APPLY SOLENOID
CHART C-8
(Page 1 of 2)
AUWBMATIC TRANSMISSION CONVERTER CLUTCH (TCC)
2.8L (VIN S) "F" SERIES (PORT)
Circuit Description:
The purpose of the automatic transmission torque converter clutch feature is to eliminate the power loss of
the torque converter stage when the vehicle is in a cruise condition. This allows the convenience of the
automatic transmission and the fuel economy of a manual transmission. The heart of the system is
a solenoid
located inside the automatic transmission which is controlled by the
ECM.
When the solenoid coil is activated ("ON"), the torque converter clutch is applied which results in straight
through mechanical coupling from the engine to transmission. When the transmission solenoid is deactivated,
the torque converter clutch is released which allows the torque converter to operate in the conventional manner
(fluidic coupling between engine and transmission).
The ECM turns
"ON" the 'KC when coolant temperature is above 65°C (14g°F), TPS not changing, and
vehicle speed above a specified value.
Test Description: Numbers below refer to circled Diagnostic Aids:
numbers on the diagnostic chart. A "Scan" tool only indicates when the ECM has 1. When a test light is connected from ALDL turned the TCC driver (grounded CKT 422), but terminal "F" to ground, a test light "ON" indicates
this does not confirm that the TCC has engaged. To battery voltage is OK and the TCC solenoid is
determine if TCC is functioning properly, engine rpm
disengaged.
should decrease when the "ScanJ' indicates the TCC
2. When the diagnostic terminal is grounded, the
driver has turned "ON". To determine if the 4th gear ECM energize the TCC "Ienoid and the switch is functioning properly, perform the checks in
test light should go out.
CIIART C-8A (Page 2 of 2). The switches will not
prevent TCC fi-om functioning but will affect TCC lock
and unlock points. If the 4th gear switch CKT is
always open the
TCC may engage as soon as sufficient
oil
pl.essure is reached.

CHART C-8
(Page 1 of 2)
AUTOMATIC TRANSMlSS18N
CONVERTER CLUKC (("FCC)
VSS WITH DRIVE WHEELS TURNING. IF CODE 24
BULB SHOULD "LIGHT."
CKT422 SHORTED TO
FROM TERM. "A" TO
OULD GO OUT.
-------------
I THE CORRECT PROM OR I I MEM-CAL. TO CHECK 4TH CONNECTOR TERMINALS
1 GEAR SWITCH, SEE CHART
I C-8A (2 OF 2).
7-14-87
8s 4679

6E3-C8-4 2.8L (VIN 5) DRIVEABILITY AND EMISSIONS
VEHICLE SPEED SIGNAL
4TH GEAR SIGNAL
422 TANIBLK
4TH GEAR SW.
TRANSMISSION
ALDL CONNECTOR
TCC APPLY SOLENOID
CHART C-8
(Page 2 of 2)
AUTOMATIC TRANSMISSION CONVERTER CLUTCH (TCC)
2.8L (VIN S) "F" SERIES (PORT)
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 I~elow 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 be
open while 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 gear the switch
should open and the "Scan" should display "YES".
4. Disconnecting the
'FCC conne tor sinlulates 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 he 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 be 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
'FCC may engage as soon as sufficient oil pressure
is reached.

DRIVEABILITY AND EMISSIONS 2.8L (VIN 5) 6E3-C8-5
TO OVERDRIVE ARNESS TERMINAL "€3" (CKT446) TO
SLOWLY UNTIL TRANS. SHIFTS
NNECT TRANS.
TRANS. IS IN 4TH GEAR?

6E3-CS-6 2.8L (VIN 5) DRIVEABILITY AND EMISSIONS
BLANK

DRIVEABILITY AND EMISSIONS 2.8L (VIN S) 6E3-C40-1
SECTION CIO
ECM CONTROLLED AIR CONDlTlOlUlNG
CONXENTS
GENERAL DESCRIPTION ................ C10-1 DIAGNOSIS ......................... C10-1
OPERATION ....................... C10-1 ON-CARSERVICE ..................... C10-1
GENERAL DESCRIPmON
In order to improve idle quality and wide open
throttle performance, the
NC compressor is controlled
by the ECM.
There are two different types of
AJC systems used
in
GM vehicles. One is referred to as C.C.O.T. (cycling
clutch orifice tube), which uses a fixed displacement
compressor. The other type of system uses a
compressor with
a variable displacement, and is
referred to as the V-5 type system. The V-5 type meets
A/C requirements without cycling. For descriptions of
both types, and an explanation of the components
used, refer to Section
"IB" of the service manual.
OPERATION
The 2.8L engine uses the C.C.O.T. type A/C
system, and is controlled by the ECM. When
NC is
requested, 12V power is supplied to the pressure
cycling switch and to the
NC power relay. The ECM
controls the
A/C clutch by energizing the A/C control
relay. This allows the
EChI to incrctlse idle speed
before turning on
NC to improve idle quality. The
high pressure cut-out switch (normally
closed) opens when head pressure gets too high. This
disables the
A/C clutch, before damage can occur to
the system. This switch opens, when pressure is
greater than about 440 psi (3034
kPa).
See CHART C-10 for diagnosis and wiring
diagram of the electrical portion of the
NC circuit.
DIAGNOSIS
CHART C-10 should be used for diagnosing the
electrical portion of the
A/C circuit. Section "1R"
should
be used for diagnosing the refrigerant portion
of the system.
The "Scan" tool will be used in diagnosing the
system, as it has the ability to read the
A/C request
input to the ECM, as well as displaying when the
ECM has commanded the
A/C clutch "ON".
ON-CAR SERVICE
For removal and replacement procedures of NC
components, refer to Section
" 1" of the service manual.