1988 PONTIAC FIERO Service Repair Manual

6E3-C8-4 5.OL (\/IN F) & 5.7b (VIN 8) DRIVEABILITY AND EMISSIONS
15-WAY I.P. CONNECTOR
SPEED INPUT
4TH GEAR SIGNAL
4TH GEAR SW.
TRANSMISSION
ALDL CONNECTOR
APPLY SOLENOID
CHART C-8A
(Page 2 of 2)
TRANSMISSION CONVERTER CLUTCH (TCC) ELECTRICAL DIAGNOSIS
5.OL (VIN F) & 5.7L (VIN 8) "F" XRlES (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 below refer to circled
numbers on the diagnostic chart.
1. Unless the switch or CKT 446 is open, the "Scan"
should display "NOJ', indicating the trans. is not
in 4th gear. The 4th gear switch should only he
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 TCC connector sin~ulates 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 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
'l'CC may engage as soon as sufficient oil pressure
is reached.

DRIVEABILIW AND EMISSIONS 5.OL (VIN F) & 5.7L (VIN 8) 6E3-C8-5
TCC ELECTRICAL CONNECTOR.
@ SHIFT VEHICLE INTO OVERDRIVE NESS TERMINAL "0" (CKT446) TO
INCREASE SPEED SLOWLY UNTIL TRANS. SHIFTS
INTO 4TH GEAR.
CAL CONNECTOR
DOES "SCAN" INDICATE

6E3-C8-6 5.OL (VIN F) & 5.7L (WIN 8) DRIVEABILITY AND EMISSIONS
15-WAY I.P. CONNECTOR
SHIFT LIGHT
CONTROL DRIVER
INSTRUMENT PANEL
CHART C-8B
NlR SI-IIFT LIGHT CHECK
5.OL (VIN F) "F" "SERIES (PORT)
Circuit Description:
The shift light indicates the best transmission shift point for maximum fuel economy. The light is controlled
by the ECM and is turned
"ON" by grounding CKT 456.
The ECM uses information from the following inputs to control the shift light:
@ Coolant temperature
@ TPS
@ VSS
@ rpm
The ECM uses the measured rpm and the vehicle speed to calculate what gear the vehicle is in. It's this
calculation that determines when the shift light should be turned "ON".
Test Description: Numbers below refer to circled 3. This checks the shift light circuit up to the ECM
numbers on the diagnostic chart.
connector.
If the shift light illuminates, then the
1. This should not turn "ON" the shift light. If the ECM connector is faulty or the ECM does not have
light is "ON", there is a short to ground in CKT
the ability to ground the circuit.
456 wiring or a fault in the ECM.
2. When the diagnostic terminal is grounded, the
ECM should ground
CKT 456 and the shift light
should come
"ON".

DRIVEABILITVAND EMISSIONS 5.OL (VIN F) & 5.7L (VIN 8) 6E3-C8-7
@ DISCONNECT ECM CONNECTORS.
@ DISCONNECT ECM CONNECTORS - CODE 24 CHART (NO VSS)
- THERMOSTAT FAULTY OR
INCORRECT HEAT RANGE.
IF OK, REVIEW SYMPTOMS
CHECK AND REPAIR: POOR
CONNECTION AT
- OPEN IGNITION CKT 39
- OPEN CKT 456

BLANK

DRlVEABlLlPV AND EMISSIONS 5.OL (VIN F) & 5.7L (VIN 8) 6E3-C"1-1
SECTION Cl2
COOLING FAN CONTROL
CONTENTS
GENERAL DESCRIPTION ................ C12-I DIAGNOSIS ......................... C1Z-1
OPERATION ..................... .. C12-1 ON-CARSERVICE ..................... C12-1
PARTS INFORMATION ................. C12-1
GENERAL DESCRIPIION DlAGNODlS
The fan is used for engine and AIC condenser
cooling but the fan only operates under certain
conditions. The
following charts will diagnose the ECM
controlled cooling fan.
Use
Sect.ion "8A" to diagnose the secondary
cooling fan.
OPERATION
ON-CAR SERVICE
The electric cooling fan on this engine is controlled
by the ECM. The ECM will ground the cooling fan
relay, which turns "ON" the fan, when the following
conditions are met.
@ Coolant temperature sensor signal indicating a
temperature greater than 106°C
(222°F).
@ AIC head pressure greater than 233 psi and
vehicle speed less than 40 mph.
When the cooling fan is turned "ON", it will stay
"ON" for a minimum time of 15 seconds. Cooling
system component replacement can be
found in Section
"6B".
PARTS INFORMATION
PART NAME GROUP
......................... Fan, Engine 1.055
......................... Motor, Fan. 1.055
.................... Relay, Engine Fan 1.055

6E3-C12-2 5.OL (VIN F) & 5.7b (VIN 8) DRIVEABILITY AND EMISSIONS
FAN CONTROL
RELAY CONN.
DK GRNNVHT 335
TEMPERATURE
SENSOR SIGNAL.
TURNS ON PRIMARY
FAN AT
223OF (1 06'C)
CHART C-12
(Page 1 of 2)
COOLING FAN CONTROL CIRCUIT
5.8L (VIN F) & 5.7L (VIN 8) "F" SSERlES (PORT)
Circuit Description:
The primary cooling fan is totally controlled by the ECM based on inputs from the coolant sensor and
fan control switch. The fan should run, if coolant temperature is greater than 106°C
(223°F).
@ Battery voltage is supplied to the fan relay on terminal "En and ignition voltage to terminal "D".
@ Grounding CKT 335 (relay terminal "F") will energize the relay and supply battery voltage to the fan
motor. Once the fan relay is energized by the
ECM, it will remain "ON" for a minimum of 15 seconds.
@ 'I'he ECM will remove the ground to CKT 335 if vehicle speed is over 40 rnph unless the engine is
overheating.
@ 'I'he fan control switch, mounted in Lhe AIC high pressure line, will close when head pressure exceeds
233 psi (1600 kPa) and this input causes the ECM to ground CKT 335.
@ If a Code 14 or 15 sets, or if the ECM is operating in the fuel back-up mode, the ECM will turn "ON"
the cooling fan.
Diagnostic Aids:
If the owner complained of an overheating If
the engine is actually overheating and the gage
problem, it must be determined if the complaint was indicates
overheating, but
t,he cooling fan is not
due to an actual boil over or the hot light or coming
"ON", the
coolant sensor has probably shifted
temperature gage indicated overheating. out
of calibration and should be replaced.
If the gate or light indicates overheating, but no If
the engine is overheating, and the cooling fan is
boilover is detected, the gage circuit should be "ON", the cooling system should be checked.
checked. The gage accuracy can also be checked by
comparing the coolant sensor reading using
a "Scan.'
tool and comparing its reading with the gage reading.

DRIVEABILITY AND EMISSIONS 5.OL (VIN F) & 5.7L (VIN 8) 6E3-C12-3
D IDLE ENGINE.
ULD
BE "OFF" (WHILE TEMP. IS UNDER
r DOES "SCAN"
INDICATE FAN IS
INALS TOGETHER.
" INDICATE FAN IS