1988 PONTIAC FIERO light

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-C10-2 2.8L (VIN S) DRIVEABILITY AND EMISSIONS
A/C CONTROL
DK GRNNVHT 59
CHART C-10
AIC CLUTCH CONTROL
2.8L (VIN S) "F" WRIES (PORT)
Circuit Description:
ECM control of the A/C clutch improves idle quality and performance by:
Delaying clutch apply
until the idle air rate is increased.
e Releasing clutch when idle speed is too low or during high power steering loilds.
e Releasing clutch a1 wide open throttle.
smooths cyclingof the compressor by providing additional fuel at the instant clutch
is applied.
Voltage is supplied to the
NC Clutch Control relay on CKT 59 by the NC Control Switch. This saine
voltage is supplied as a signal to ECM pit1 88. After a time delay of about 112 second the ECM twill ground
terminal
"A2," CKT 905, and close the A/C relay contacts.
When
relay is energi~etf battery vollage from CKT 59 is supplied to the IVC clulch lhroug11 Ihe txlay arid
CKT 959.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. The ECM will only energize the A/C relay, when
the engine is running.
'I'his lest will determine if
the relay, or CK'F 905, is Sauity.
2. In order for the clutch to proper1.y be engaged, the
pressure cycling switch must bc closc!cl to provide
12 volts to the relay,
ilnd the high pressure switch
must be closed, so the
AlC rtquest (12 volts) wlll
be present at the ECNI.
3. Determines if the signal is ~.eachitlg the I4:CAI on
CKT 59 from the A/C control panel. Signal hhoitld
only be present when the AlC mode or tlcl'rost
mode has been selected.
4. A short to ground in any part ot' the A/C request
circuit, CKT
67 to the relay CKrI' 59, CKT 959 to
the NC clutch, or the
:2/C clutch, coulcl be the
cause
ofthe blown fiise.
5. With the ignition "ON" and the diagnostic
tcrminal grounded, the ECM should be grounding
CKT 905 which should cause the test light to be
"ON".
Diagnostic Aids:
If complaint was insufficient cooling, the problem
111~1,~ be ciiuscd by an inoperalive cooling fan. 'I'he
t!11gine cooling fan should turn "ON," when AlC is
"ON" ,tntl cZ/C head pressure exceeds about 233 psi. If
not. qctt: ("I Iclli'I' C-12 for diagnosing the cooling fan.

CONNECTOR
TO ALTERNATOR
I.P.CONNECTOR
DK GRNNVHT 335
CHART C-12
(Page 1 of 2)
COOLING FAN CONTROL CIRCUIT
2.8L (VIN S) "F" SERIES (PORT)
Circuit Description:
'I'he electric cooling fan is controlled by the ECM, based on inputs from the coolant temperature sensor, the
NC fan control switch, and vehicle speed. 'I'he ECM controls the f~in by grounding CKT 335, which energizes
the fan control relay. Battery voltage is then supplied to the fan motor.
The ECM grounds
CKT 335, when coolant temp. is over about 106°C (223"F), or when AIC has been
requested, and the fan control switch opens with high
I\/C pressure, about 200 psi (1380 kPa). Once the ECM
turns the relay "ON", it will keep it "ON" for a nlinirnum of GO seconds, or until vehicle speed exceeds 70 mph.
Also, if Code
14 or 15 sets, or the ECM is in throttle body back up, the fan will run at all times.
On
kt vehicle not equipped with A/C, CK'I' 732 is,ju~rlperetl to ground so that Lhe fan does not run at all times.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart,.
1. With the diagnostic terminal grounded, the
cooling
fan control driver will close, which should
energize the fan control
relay.
2. If the A/C fan control switch or circuit is open, the
fan would run whenever the engine is running.
3. With AIC clutch engaged, the i\lC fan control
switch should open, when
A/C high pressure
exceeds about
200 psi ( 1380 k13a). This signal
should cause the
ECM to energize the ran control
relay.
Diagnostic Aids:
If the owner complained of an overheating
problem, it
rnust he determined if the complaint was
clue to an actuill hoilover, or the hot light, or
temperature gage indicated over heating.
If the gage, or light, indicates overheating, but no
hoilover is detected, the gage circuit should he
checked.
'I'he gage accuracy can, also, be checked by
comparing the coolant sensor reading using a "Scan"
tool and comparing its reading with the gage reading.
If the engine is actually overheating, and the gage
indicates overheating, but the cooling fan is not
coming "ON", the coolant sensor has probably shifted
out
ofcalibration and should be replaced.
If
the engine is overheating, and the cooling fan is
"ON", the cooling system should hc checked.

6E3-C12-4 2.8L (VIN S) DRIVEABILITY AND EMISSIONS
I.P. HARNESS CONNECTOR
(FRONT VIEW)
TO ALTERNATOR
DK GRNNVHT 335
FAN CONTROL SWITCH
CHART C-12
(Page 2 of 2)
COOLING FAN CONTROL CIRCUIT
2.8L (VIN S) "F" SERIES (PORT)
Test Description: Numbers below refer to circled
The SES light should also be flashing, at this
numbers on the diagnostic chart.
point. If it isn't flashing, see
CHART A-2.
1. 12 volts should be available to both terminal "E" 3. If the fan docs not turn "ON", at this point, CKT
& "C", when the ignition is "ON". 936 or CKT 150 is open, or the cooling fan motor is
2. This test checks the ability of the ECM to ground
faulty.
CK'I' 335.

DRIVEABILITY AND EMISSIONS 5.OL (VIM F) & 5.7L(VIN 8) 6E3-A-1
DIAGNOSIC CIRCUIT CHECK Cold Oxygen Sensor
The "Diagnostic Circuit Check" verifies the On some engines. the Oxygen Sensor will cool off
system is functioning correctly
. Some special after only a short period of operation at idle . This will
considerations to keep in mind while making the put the system into "Open Loop"
. To restore "Closed
"Diagnostic Circuit Check" are:
I. oop" operation. run the engine at part throttle
several minutes and accelerate from idle to part
Blocking Drive Wheels throttle a few times .
The vehicle drive wheels must be blocked while Basic Procedure
checking the system .
If you have not reviewed the Basic Information on
how to use the Diagnostic Procedures. go to the
Introduction of this section
.
SECTION A
ENGINE COMPONENTS
/WIRING DIAGRAMS 1 DIAGNOSTIC CHARTS
........................................................ Component Locations Page A-2
...................................................... Wiring Diagrams. (1 of 4) Page
A-3
ECMTerminal EndView ...................................................... PageA-7
.................................................. Scan Diagnostic Circuit Check Page
A-8
........................................ . No "Service Engine Soon" Light Chart A-I Page A-10
No ALDL Data
. "Service Engine Soon" Light On Steady (Won't Flash Code 12) . Chart A-2 ..... Page A-12
................................... . Engine Cranks But Won't Run Chart A.3, (1 of 2) Page A-14
......................................... Fuel System Diagnosis . Chart A.7, (1 of 2) Page
A-18
.................................................... . Cold Start Valve Chart A-9 Page A-22
..................................................... Code 13 O2 Sensor Circuit Page
A-24
.................................. Code 14 Coolant Temperature Sensor Circuit (High) Page
A-26
.................................. Code 15 Coolant Temperature Sensor Circuit (Low) Page
A-28
................................. Code 2 I Throttle Position Sensor (TPS) Circuit (High) Page
A-30
.................................. Code 22 Throttle Position Sensor (TPS) Circuit (Low) Page
A-32
......................... Code 23 Manifold Air Temperature (MAT) Sensor Circuit (Low) Page
A-34
........................................ Code 24 Vehicle Speed Sensor (VSS) Circuit Page
A-36
......................... Code 25 Manifold Air Temperature (MAT) Sensor Circuit (High) Page
A-38
..................................... Code 32 Exhaust Gas Recirculation (EGR) Circuit Page
A-40
................................... Code 33 Mass Air Flow (MAF) Sensor Circuit (High) Page
A-42
................................... Code 34 Mass Air Flow (MAF) Sensor Circuit (Low) Page
A-44
................................. Code 36 Mass Air Flow (MAF) Sensor Burn-Off Circuit Page
A-46
................................................... Code 41 Cylinder Select Error Page
A-48
...................................... Code 42 Electronic Spark Timing (EST) Circuit Page
A-50
...................................... Code 43 Electronic Spark Control (ESC) Circuit Page
A-52
............................................ Code 44 Oxygen Sensor Circuit (Lean) Page
A-54
............................................. Code 45 Oxygen Sensor Circu~t (Rich) Page
A-56
......................................... Code 46 Vehicle Anti Theft System (VATS) Page
A-58
Code51
MEM.CAL ........................................................... PageA-62
........................................................ Code52CALPAKError PageA-62
................................................... Code 53 System Over Voltage Page
A-62
................................................ Code 54 Fuel Pump Circu~t (Low) Page
2-60

6E3-A-2 5.OL (VIN F) & 5.7L(VIN 8) DRIVEABILITY AND EMISSIONS
COMPUTER HARNESS [7 CONTROLLED DEVICES 0 INFORMATION SENSORS
C1 Electronic Control Module (ECM) 1 Fuel injector €3 Exhaust oxygen
C2 ALDL diagnostic connector 2 Idle air control motor C Throttle position
C3 "SERVICE ENGINE SOON" light
3 Fuel pump relay D Coolant temperature
C4
ECMpower 5 Trans. Converter Clutch connector F Vehicle speed
C5 ECM harness ground
7 Electronic Spark Control module J ESCknock C6 Fuse panel
C8 Fuel pump test connector (ALDL "G") Primary fan relay K Mass Air Flow
C9 Fuel pump1ECM fuse 9 Air injection converterldivert solenoid T Manifold Air Temperature
10 Air injection port solenoid
U AIC pressure fan switch . ., .. .. NOT ECM CONNECTED 12 EGR vacuum solenoid w EGR temp. diagnostic switch
N1 Crankcase vent valve (PCV) 15 Fuel vapor canister solenoid
N5 Engine temp. sensor (gage overheat)
16 MAF sensor power relay
N7 Oil pressure sensor (gage) 17 MAF sensor burn-off relay
N8 Oil pressure switch (fuel pump) 18 Primary cooling fan
N10 Cold start valve
N11 Cold start fuel injection switch
N12 Secondary cooling fan
N13 Cooling fan temperature switch
N14 Secondary cooling fan relay 7-13-87
*8S 4274-6E
Figure A-I - Component
Locations - 5.OL (WIN F) & 5.7L (WIN 8) "F" Series