1988 PONTIAC FIERO Service Repair Manual

6E2-C1-14 DRlVEABlLlTV AND EMISSIONS - 5.OL (VIN E)
806 PPUWHT CRANK SIGNAL
STARTER SOLENOID
('HOT' DURING CRANK)
CHART C-l B
CRANK SIGNAL
5.OL (VIN E) "F" "SERIES (TBI)
Circuit Description:
Crank signal is a 12 volts signal to the ECM during cranking to allow enrichment and cancel diagnostics
until engine is running and 12 volts is no longer on circuit.
Test Description: Numbers below refer to circled 2. Checks to determine if source of blown fuse was a
numbers on the diagnostic chart. faulty
ECM.
1. Checks for normal (cranking) voltage to terminal
"C9" of ECM. Test light should be "ON" during
cranking.

DRIVEABILITY AND EMISSIONS - 5.0b (VIN E) 6E2-C9-15
RECHECK FUSE.
CLEAR CODES AND CONFIRM "CLOSED LOOP" OPERATION AND NO "SERVICE
ENGINE SOON" LIGHT.

6EZ-C1-16 DRIVEABILITY AND EMISSIONS - 5.OL (VIN E)
MAP SIGNAL
CHART C-l D
MAP OUTPUT CHECK
5.OL (VIN E) 'T" SERIES (TBI)
Circuit Description:
The manifold absolute pressure sensor (MAP) measures manifold pressure (vacuum) and sends that signal
to the ECM. The ECM uses this information for fuel and spark control.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. Checks MAP sensor output voltage to the ECM.
This voltage, without engine running, represents
a barometer reading to the ECM.
2. Applying 34 kPa (10 inches Hg) vacuum to the
MAP sensor should cause the voltage to be 1.2
volts less than the voltage at Step 1. Upon
applying vacuum to the sensor, the change in
voltage should be instantaneous. A slow voltage
change indicates
a faulty sensor.
3. Check vacuum hose to sensor for leaking or
restriction. Re sure no other vacuum devices are
connected to the MAP hose.
Diagnostic Aids:
With the ignition "ON" and the engine stopped,
the
manifold pressure is equal to atmospheric
pressure and the signal voltage will be high. This
information is used by the ECM as an indication of
vehicle altitude and is referred to as BARO.
Comparison of this
BARO reading with a known good
vehicle with the same sensor is a good way to check
accuracy of a "suspect" sensor. Reading should be the
same,
f .4 volt.

BWlVEABlLlTY AND EMISSIONS - 5.OL (VIM E) 6E2-CI-I7
0") OF VACUUM AND
CHANGE. (VOLTAGE
- 2.3 VOLTS LESS THAN
VOLTAGE RANGE I
1 Below 305 Below 1,000 1 305s- 61 0 1,000--2,000 I 610--- 914 2,000--3,000 1 91 4--1219 3,000--4,000 I 1219--1524 4,000--5,000 1 1524-1829 5,000--6,000 I 1829--2133 6,000--7,000 1 21 33--2438 7,000--8,000 I 2438--2743 8,000--9,000 1 2743--3048 9,000--10,000 I I LOWALTITUDE = HIGH PRESSURE = HIGH VOLTAGE I L------------------------------------------J

6E2-C1-18 DRIVEABILITY AND EMISSIONS - 5.OL (VIN E)
CHART C-1 E
POWER SEERING PRESSURE SWIKCH (PSPS) DIAGNOSIS
5.0L (VIN E) "F" SERIES (TBI)
Circuit Description:
The power steering pressure switch is normally open to ground, and CKT 901 will be near the battery
voltage. Turning the steering wheel increases power steering oil pressure and its load on an idling engine. The
pressure switch will close before the load can cause an idle problem.
Closing the switch causes CKT 901 to read less than
1 volt and the ECM will increase the idle air rate and
de-energize the
AJC relay.
A pressure switch that will not close, or an open CKT 901 or 450, may cause the engine to stop when
power steering loads are high.
A switch that will not open, or a CKT 901 shorted to ground, may affect idle quality, and will cause the
AJC relay to be de-energized.
Test Description: Numbers below refer to circled 2. Checks to determine if CKT 901 is shorted to
numbers on the diagnostic chart. ground.
1. Different
makes of "Scan" tools may display the 3. This should simulate a closed switch.
state of this switch in different ways. Refer
to
"Scan" tool upgrading to determine how this input
is indicated.

DRIVEABILITY AND EMISSIONS - 5.OL (VIN E) 6E2-C1-19
CHART C-1 E
BOWER SEERING PRESSURE
r TURN STEERING WHEEL AGAINST STOP.
@ JUMPER HARNESS
r "SCAN" SHOULD
CHASSIS GROUND.

6E2-C1-20 DRIVEABILlf V AND EMISSIONS - 5.OL (VIN E)
BLANK

DRIVEABILIW AND EMISSIONS - 5.OL (VIN E) 6E2-62-1
SECTION C2
FUEL CONTROL SYSTEM
TBI MODEL 228
CONTENTS
GENERAL DESCRIPTION . . . . . . . . . . . . . . . C2-1
PURPOSE ......................... C2-1
MODES OF OPERATION . . . . . . . . . . . . . . C2-1
Starting Mode . . . . . . . . . . . . . . . . . . . C2-1
Clear Flood Mode . . . . . . . . . . . . . . . . C2-2
RunMode . . . . . . . . . . . . . . . . . . . . . . C2-2
Open Loop . . . . . . . . . . . . . . . . . . . . . . C2-2
Closed Loop . . . . . . . . . . . . . . . . . . . . . C2-2
Acceleration Mode . . . . . . . . . . . . . . . C2-2
Deceleration Mode . . . . . . . . . . . . . . . C2-2
Battery Correction Mode . . . . . . . . . . . C2-2
Fuel Cut Off Mode . . . . . . . . . . . . . . . . C2-2
FUEL CONTROL SYSTEM COMPONENTS
. . . C2-2
BASIC SYSTEM OPERATION . . . . . . . . . . . C2-3
THROTTLE BODY INJECTION (TBI) UNIT. . . C2-3
Fuel Injectors . . . . . . . . . . . . . . . . . . . . C2-3
Pressure Regulator . . . . . . . . . . . . . . . C2-3
ldle Air Control (IAC) Valve . . . . . . . . . . C2-4
Throttle Position Sensor (TPS) . . . . . . . . C2-4
FUEL PUMP.. . . . . . . . . . . . . . . . . . . . . . . C2-5
FUEL PUMP ELECTRICAL CIRCUIT . . . . . . . C2-5
DIAGNOSIS . . . . . . . . . . . . . . . . . . . . . . * C2-5
FUEL CONTROL . . . . . . . . . . . . . . . . . . . . C2-5
GENERAL DESCRIPTION
PURPOSE
The basic function of the fuel control system is to
control fuel delivery to the engine. Fuel is delivered to
the engine by
a throttle body injection ('FBI) unit.
ENGINE CONTROL MODULE (ECM)
EXHAUST OXYGEN (0,) SENSOR
I 1 THROTTLE BODY INJECTION UNIT (TBI)
CATALYTIC CONVERTER
8P 0352 SYE a 3 81
Figure C2-1 - Closed Loop System
ldle Air Control Valve (IAC) . . . . . . . . . C2-5
Driveability . . . . . . . . . . . . . . . . . . . .. C2-5
ON VEHICLE SERVICE
. . . . . . . . . . . . . . . . . C2-5
GENERAL SERVICE INFORMATION . . . . . . C2-5
Fuel Pressure Relief . . . . . . . . . . . . . . . C2-7
Fuel System Pressure Test . . . . . . . . . . . C2-7
Cleaning and Inspection . . . . . . . . . . . C2-7
Thread Locking Compound . . . . . . . . . C2-7
FUEL METER COVER ASSEMBLY . . . . . . . . C2-7
FUEL INJECTOR ASSEMBLIES . . . . . . . . . . C2-8
FUEL METER BODY ASSEMBLY . . . . . . . . . C2-9
THROTTLE POSITION SENSOR (TPS) . . . . . C2-10
IDLE AIR CONTROL (IAC) VALVE . . . . . . . . C2-11
THROTTLEBODYASSEMBLY .......... C2-11
MINIMUM IDLE SPEED CHECK.. . . . . . . . . C2-12
THROTTLE BODY INJECTION (TBI) UNIT.. . C2-I3
FUEL HOSEIPIPE ASSEMBLIES . . . . . . . . . . C2-13
Materials . . . . . . . . . . . . . . . . . . . . . . C2-13
Fuel Line Repair . . . . . . . . . . . . . . . . . . C2-13
FUEL PUMP RELAY . . . . . . . . . . . . . . . . . . C2-13
OIL PRESSURE SWITCH . . . . . . . . . . . . . . . C2-13
PARTS INFORMATION
. . . . . . . . . . . . . . . . . C2-14
The main control sensor is the oxygen (02) sensor,
which is located in the exhaust manifold. The
O?
sensor tells
the engine control module ECM the
amount of osygen in the exhttust gas, and the ECM
changes the airtfuel ratio to the engine by controlling
the fuel injector.
A 14.7: 1 aidfuel ratio is required for
efficient catalytic converter operation. Because of the
constant measuring and adjusting of the
airlfuel ratio,
the fuel injection system is called a "Closed
IAoopP
System (Figure C2 -1).
MODES OF OPERATION
The ECM monitors voltages from several sensors
to determine how
much fuel to give the engine. The
fuel is delivered under one of several conditions, called
"modes." All the modes are controlled by the ECM.
Starting Mode
When the key is first turned "ON", the ECM turns
on the fuel pump relay for two seconds,
i~nd the l'uel
pump builds up pressure to the TRI unit. The ECM
checks the coolant
temperature sensor, throttle
position sensor
('UPS), manifold absolute pressure
(MAP) sensor, and crank signal, then determines the
proper airtfuel ratio tbr starting. This ranges from