sensor PONTIAC FIERO 1988 Service Repair Manual

DWI\/EABILITV AND EMISSIONS 2.8L (VIN 5) 6E3-B-5
CU"T SUP, MISSES
Definition: Steady pulsation or jerking that follows engine
speed, usually more pronounced as engine load increases. The
exhaust has a steady spitting sound at idle or low speed.
@ Perform careful visual check as described at
start of Section
"B".
@ Check for missing cylinder by:
1. Disconnect IAC valve. Start engine.
Remove one spark plug wire at a time
using insulated pliers.
2. If there is an rpm drop on all cylinders
(equal to within
50 rpm), go to "ROUGH,
UNSTABLE, OR INCORRECT IDLE,
STALLING" symptom. Reconnect IAC
valve.
3. If
there is no rprn drop on one or more
cylinders, or excessive variation in drop,
check for spark on the suspected
cylinder(s) with J 26792 (ST-125) Spark
Gap Tool or equivalent.
If no spark, see
Section
"6D" for intermittent operation or
miss. If there is spark, remove spark
plug(s) in these cylinders and check for:
- Cracks
- Wear
- Improper gap
- Burned electrodes
- Iieavy deposits
@ Perform compression check on questionable
cylinder(s) found above. If compression is low,
repair as necessary. See Section
"6".
@ Disconnect all injector harness connectors.
Connect
5-34730-2 injector test light or
equivalent 6 volt test light between the
harness terms, of each injector connector and
note light while cranking. If test light fails to blink
at any connector, it is a faulty injector drive
circuit harness, connector, or terminal.
@ Perform the injector balance test. See CHART C-
2A.
s CHECK:
- Spark plug wires by connecting ohmmeter to
ends of each wire in question. If meter reads over
30,000 ohms, replace wire(s1.
- Fuel System - Plugged fuel filter, water, low
pressure. See
CHART A-7.
- Valve timing.
- Secondary voltage using a shop ocilliscope or a
spark tester 5-26792 (ST-125) or equivalent.
@ Visually inspect distributor cap and rotor for
moisture, dust, cracks, burns, etc. Spray cap and
plug wires with, fine water mist to check for
shorts.
@ A miss condition can be caused by EM1
(Electromagnetic Interference) on the reference
circuit.
EM1 can usually be detected by
monitoring engine rpm with a "Scan" tool. A
sudden increase in rpm with little change in
actual engine rpm change, indicates
EM1 is
present. If the problem exists, check routing of secondary
wires, check all distributor ground circuits.
@ Remove rocker covers. Check for bent pushrods,
worn rocker arms, broken valve springs, worn
camshaft lobes. Repair as necessary. See Section
"6A".
BACKFIRE
Definition: Fuel ignites in intake manifold, or
in exhaust system, making a loud popping noise.
CHECK:
- Loose wiring connector or air duct at MAF
sensor.
- Compression - Look for sticking or leaking
valves.
- EGR operation for being open all the time. See
CHART C-7.
- EGR gasket for faulty or loose fit .
- Valve timing.
- Output voltage of ignition coil using a shop
ocilliscope or spark tester 5-26792 (ST-125) or
equivalent.
- Spark plugs for crossfire also inspect (distributor
cap, spark plug wires, and proper routing of plug
wires).
- Ignition system for intermittent condition. (See
Section
"6D").
- Engine timing - see Emission Control
Information label.
- Perform fuel system diagnosis check, CIIART A-
7A.
- Perform injector balance test, CHART C-2A.
- Deceleration valve (2.8L ~nanualltrans) - See
Section
"C6".
- A.I.R. system check valves - See Section "C-6".

6E3-B-6 2.8L (VIN 5) DRIVEABILITY AND EMISSIONS
POOR FUEL ECONOMY
Definition: Fuel economy, as measured by an actual road test, is
noticeably lower than expected. Also, economy is noticeably lower than
it was on this car at one time, as previously shown by an actual road test.
@ Perform careful visual check as described at
start of Section "B".
8 CHECK:
- Coolant level.
- Engine thermostat for faulty part (always
open) or for wrong heat range. See Section
"6B".
- Compression
- Ignition timing. See Emission Control
Information label.
- TCC for proper operation. A "ScanJ' should
indicate an rpm drop when the TCC is
commanded "ON". See CHART C-8.
- Induction system and crankcase for air leaks.
8 Check for exhaust restriction.
See CHART
B-1.
DIESELING, RUN-ON
Definition: Engine continues to run after key is
turned "OFF", but runs very roughly. If engine runs
smoothly, check ignition switch and adjustment.
8 Check injectors for leaking. See CHART A-7.
ROUGH, UNSTABLE, OR INCORRECT IDLE, STALLING
Definition: The engine runs unevenly at idle. If bad enough, the car may
shake. Also, the idle may vary in rpm (called "hunting"). Either
condition
may be bad enough to cause stalling. Engine idles at incorrect speed.
@ Perform careful visual check as described at
start of Section "B".
@ CHECK:
- Throttle linkage for sticking or binding. Also
check TPS adjustment. Refer to Section
"C2".
- Ignition timing. See Emission Control
Information label.
- ECM ground circuits.
- IAC system. See CHART C-2C.
- Generator output voltage. Repair if less than 9
or more than 16 volts.
- PIN switch circuit. See CHART C-lA, or use
"SCAN" tool.
- Injector balance. See CHART C-'LA.
- PCV valve for proper operation by placing
finger over inlet hole in valve end several times.
Valve should snap back. If not, replace valve.
- Evaporative Emission Control System. CHART
C-3.
- A/C signal to ECM terminal "B8" (5.OL & 5.7L).
"Scan" tool should indicate AIC is being
requested when ever
A/C is selected and the
pressure cycling switch is closed.
- A/C system operation (2.8L) - See CHAR'l' (2-10.
- Minimum idle speed. See Section "C2".
- Loose or damaged MAF sensor duct between
sensor and throttle body.
- Power Steering Pressure Switch (2.81, - See
CHART
C-1E.
Check AIR system. There should be no AIR to
ports while in "Closed Loop". See CHART C-6.
EGR valve: There should be no EGR at idle.
Run a cylinder compression check. See Section
"6". Inspect oxygen sensor for silicon contamination
from fuel, or use of improper RTV sealant. The
sensor will have a white, powdery coating, and
will result in a high but false signal voltage (rich
exhaust indication). The ECM will then reduce
the
amount of fuel delivered to the engine,
causing a severe driveability problem.
Check for fuel in pressure regulator hose. If
present replace regulator assembly.
Check ignition system; wires, plugs, rotor, etc.
Check for loose or damaged air duct between
MAF sensor and throttle body.
Ilisconnect MAF sensor and if condition is
corrected replace sensor.
Clean injectors.
Monitoring block learn will help identify the
cause of the problem. If the system is runnig lean
(block learn greater than
138), refer to
"Diagnostic Aids" on facing page of Code
44. If
the system is running rich (block learn less than
118), refer to "Diagnostic Aids'' on facing page of
Code 45.

CHART B-l
RESTRICTED EXHAUST SYSEEM CHECK
ALL ENGINES
Proper diagnosis for a restricted exhaust system is essential before any components are replaced. Either of
the following procedures may be used for diagnosis, depending upon engine or tool used:
CHECK AT A. I. R. PIPE: - OR
1. Remove the rubber hose at the exhaust
manifold A.I.R. pipe check valve. Remove
check valve.
2. Connect a fuel pump pressure gauge to a hose
and nipple from a Propane Enrichment
Device (526911) (see illustration).
3. Insert the nipple into the exhaust manifold
A.I.R. pipe.
GAGE
1 HOSE AND NIPPLE ADAPTER
1 3,I.R. PIPE (EXHAUST PORT)
1 CHECK VALVE 7s 3363-6E
CHECK AT 02 SENSOR:
1. Carefully remove 02 sensor.
2. Install Borroughs Exhaust Backpressure
Tester (BT 8515 or BT 8603) or equivalent in
place of
02 sensor (see illustration).
3. After
completing test described below, be
sure to coat threads of
02 sensor with anti-
seize compound PIN 5613695 or equivalent
prior to re-installation.
DIAGNOSIS:
1. With the engine idling at normal operating temperature, observe the exhaust system backpressure
reading on the gauge. Reading should not exceed
I $ psi (8.6 kPa).
2. Accelerate engine to 2000 RPM and observe gauge. Reading should not exceed 3 psi (20.7 kPa).
3. If the backpressure, at either RPM, exceeds specification, a restricted exhaust system is indicated.
4. Inspect the entire exhaust system for a collapsed pipe, heat distress, or possible internal muffler failure.
5. If
there are no obvious reasons for the excessive backpressure,
a restricted catalytic converter should be
suspected and replaced using current
recom~nended procedures.

6E3-C-1 2.8L (VIN S) DRIVEABILITY AND EMISSIONS
COMPONENT SYSTEMS
Section C provides information on the following:
@ General description of components and systems .
e On-vehicle service .
@ Part names and group numbers .
@ Diagnostic charts . These include a functional check of the system as well as diagnosis of any problem
found in the functional check
.
For locations of components. wiring diagrams and ECM Terminal End View refer to the front of the A Sections of
the engine being diagnosed
.
Following are the sub-section identification and the system covered:
Electronic Control Module (ECM) and Sensors
........................... Page C1-I
Fuel Control System ............................................... Page C2-1
Evaporative Emission Control (EECS) System ............................ Page C3-1
Ignition SystemIEST ............................................... Page C4-1
Air Injection Reaction (A.I.R.) System Manual Transmission Only .............. Page C6-1
Exhaust Gas Recirculation (EGR) System ................................ Page C7-1
Transmission Converter Clutch (TCC) System and Manual Transmission Shift Light Page C8-1
ECM Controlled Air Conditioning .................................... Page C10-I
Cooling Fan Control ............................................... Page C12-1
Positive Crankcase Ventilation (PCV) .................................. Page C13-1
DIAGNOSTIC CHARTS
The Diagnostic Charts for each system are found after the on-car service and parts information at the back of
each section
. Following are the charts found in this section .
@ Chart C-I
@ Chart C-1A
e ChartC-1E
@ Chart C-2A
e Chart C-2C
@ Chart C-3
@ Chart C-4A
@ Chart C-6
@ Chart C-7
@ Chart C-8
@ Chart C-8
@ Chart C-10
@ Chart C-12
@ Chart C-12 ECM
QDR Check ........................................... Page C1-10
Park
Neutral Switch ........................................ Page C1-12
Power Steering Pressure Switch Check .......................... Page C1-14
Injector Balance Test ....................................... Page C2-18
Idle Air Control ........................................... Page C2-20
Canister Purge Valve Check .................................. Page C3-4
Ignition System Check ...................................... Page C4-4
Electric Control (Divert) . (Manual Transmission) .................. Page C6-6
Exhaust Gas Recirculation Check .............................. Page C7-6
Automatic Transmission Converter Clutch (TCC) . 1 of 2 ............. Page C8-2
Automatic Transmission Converter Clutch (TCC) . 2 of 2 ............. Page C8-4
NC Clutch Control ......................................... Page C10-2
. ............. ............... Cooling Fan Control Circuit 1 of 2 Page C12-2
. ............................. Cooling Fan Control Circuit 2 of 2 Page C12-4

DRIVEABILITY AND EMISSIONS 2.8L WIN S) 6E3-C1-1
SECTION C1
ELECTRONIC CONTROL MODULE (ECM) AND SENSORS
CONTENTS
GENERAL DESCRIPTION ................ C1-1 MAF Sensor ..................... C1-5
ELECTRONIC CONTROL MODULE (ECM) , . C1-1 MAT Sensor ..................... C1-5
ECMTYPES.. ...................... C1-I O2 Sensor ....................... C1-5
PROM ........................... C1-1 TPS............................ C1-5
CALPAK .......................... C1-2 VSS ........................... C1-5
ECM Function..
.................. C1-2 PIN Switch ...................... C1-5
INFORMATION SENSORS ............. C1-2 A/C Request Signal ................ C1-5
........ Engine Coolant Temp. Sensor C1-2 Power Steering Pressure Switch ...... C1-5
Mass Air Flow (MAF) Sensor ......... C1-2 Reference Signal ................. C1-5
A/C MAF Sensor .................. C1-2 ON-CAR SERVICE ..................... C1-5
..... Manifold Air Temp. (MAT) Sensor C1-2 ELECTRONIC CONTROL MODULE (ECM) . . C1-5
Oxygen (Oz) Sensor ............... C1-3 ECM & COMPONENTS REPLACEMENT
........ Throttle Position Sensor (TPS) C1-3 PROMORECM ..................... C1-6
Vehicle Speed Sensor
.............. C1-3 Functional Check ................. C1-7
...... ParkINeutral Switch (Auto Only) C1-4 CALPAK.......................... C1-7
AIC "ON" Signal .................. C1-4 COOLANTSENSOR .................. C1-7
Distributor Reference Signal
......... C1-4 MAFSENSOR ...................... C1-7
DIAGNOSIS ......................... C1-4 MAF SENSOR POWER & BURN-OFF RELAY. C1-7
ECM .......e.........e........... C1-4 OXYGENSENSOR ................... C1-8
PROM ........................... C1-4 Throttle Position Sensor ............ C1-8
ECM Inputs..
.................... C1-5 PARKJNEUTRALSWITCH .............. C1-9
Coolant Temp. Sensor ............. C1-5 PARTS INFORMATION ................. C1-9
GENERAL DESCRIPTION
ELECTRONIC CONTROL MODULE (ECM)
The electronic control module (ECM) (Figure C1-
I), located under the instrument panel, is the control
center of the fuel injection system. It constantly looks
at the information from various sensors, and controls
the systems that affect vehicle performance. The ECM
performs the diagnostic function of the system. It can
recognize operational problems, alert the driver
through the "Service Engine Soon"
light, and store a
code or codes which identify the problem areas to aid
the technician in making repairs. See "Introduction"
for more information on using the diagnostic function
of the ECM.
ECM TYPES
There are two types of ECM'S used for "I?" series
vehicles equipped with port fuel engines:
Vehicles equipped with a
2.8L engine will use an
ECM referred to as GMCM. For
service, the ECM
consists of three parts: a Controller (the ECM without
a PROM), a separate Calibrator (PROM), and a
CALPAK.
ECM PROM ACCESS COVER I
1 ECM HARNESS
CONNECTORS TO ECM
Figure C1-1 Electronic Control Module (ECM)
PROM
To allow one model of ECM to be used for many
different cars, a device called a Calibrator (or PROM)
(Programmable Read Only Memory) is used (see
Figure
C1-2). The PROM is located inside the ECM,
and has information on the vehicle's weight, engine,

6E3-C1-2 2.8L (VIN S) DRIVEABILITY AND EMISSIONS
transmission, axle ratio, and several others. While one
ECM part number can be used by many car lines, a
PROM is very specific and must be used for the right
car. For this reason, it is very important to check the
latest parts book and Service Bulletin information for
the correct part number when replacing a PROM.
An ECM used for service (called a controller)
comes without a PROM. The PROM from the old ECM
must be carefully removed and installed in the new
ECM (see On-Car Service).
CALPAK (Fig. C1-2)
A device called a CALPAK is used to allow fuel
delivery if other parts of the ECM are damaged.
It has an access door in the ECM, and removal and
replacement procedures are similar to the PROM
removal procedures.
The CALPAK must be transferred to a
replacement ECM.
M (ENGINE CALIBRATOR)
Figure C1-2 PROM (Calibrator) and CALPAK
ECM Function
The ECM supplies either 5 or 12 volts to power
various sensors or switches. This is done through
resistances in the ECM which are so high in value
that
a test light will not light when connected to the
circuit. In some cases, even an ordinary shop
voltmeter will not give an accurate reading because
its resistance is too low. Therefore, a 10
Meg Ohm
input impedance digital voltmeter is required to
assure accurate voltage readings.
The ECM controls output circuits such as the
Injector, IAC, Cooling Fan Relay, etc. by controlling
the ground circuit
thr0ug.h transistors in the ECM.
Engine Coolant Temperature Sensor
(Fig.CI-3)
The coolant sensor is a thermistor (a resistor
which changes value based on temperature) mounted
in the engine coolant stream.
Low coolant
temperature produces a high resistance
( 100,000 ohms
at -40°C/-40°F) while high temperature causes low
resistance (70 ohms at
130"C/26fi°F).
ENGINE COOLANT TEMPERATURE SENIOR
HARNESS CONNECTOR TO ECM
4-2-85 LOCKING TAB *5S 4640-6EA
Figure C1-3 Engine Coolant Temperature Sensor
The ECM supplies a 5-volt signal to the coolant
sensor thru a resistor in the ECM
and measures thc
voltage. The voltage will be high when the engine is
cold, and
low when the engine is hot. t3y measuring
the voltage, the ECM knows
the engiao coo/ant
temperature. Engine coolant temperature aifeces most
systems the ECM controls.
A failure
in the coolant sensor circuit should set
either a Code 14 or Code 15. Remember, these codes
indicate a failure in the coolant temperature circuit,
so proper use of the chart will
lead to either repairing
a wiring problem or replacing the sensor, to properly
repair a problem.
Mass Air F10w (MAF) Sensor
Figure C1-4
The mass air flow (MAF) sensor measures the
amount of air which passes through it.
'I'he ECM uses
this information to determine the operating condition
of the engine, to control
fuel delivery. A large
quantity of air indicates acceleration, while a small
quantity indicates deceleration or idle.
NC MAF Sensor
'I'he MAF sensor produces a frequency output
which is proportional to the air entering the en,'
alne.
The output will vary from about 32 hertz at idle to 150
hertz at WOT. If the sensor fails at a low frequency, a
Code 34 should set. If the sensor fails at a high
frequency, a
Code 33 should set. A Code 44 or 45 may
also be caused by a faulty
MAF sensor.
'I'he code charts will explain how to determine if
the sensor is causing the rich or lean condition.
Manifold Air Temperature (MAT) Sensor
The manifold air temperature (MAT) sensor is a
thermistor
(a resistor which changes value based on
temperature mounted in the
air cleaner assembly.
1,ow temperature produces a high resistance (100,000
ohms at -40°C/-400F) while high temperature causes
low resistance (70 ohms at
130"C/2G6"F).

The ECM supplies a 5-volt signal to the sensor
thru
a resistor in the ECM and measures the voltage.
The voltage will be high when the manifold air is cold,
and low when the air is hot. By measuring the
voltage, the ECM knows the manifold air
temperature.
The
2.8L uses the signal to slightly retard the
timing during high ambient air temperatures and to
help compensate the MAF sensor based on air
temperature.
A failure in the MAT sensor circuit should set
either a Code
23 or Code 25.
Oxygen (02) Sensor (Fig. C1-4)
The exhaust oxygen sensor (02) is mounted in the
exhaust system where it can monitor the oxygen
content of the exhaust gas stream. The oxygen content
in the exhaust reacts with the sensor to produce a
voltage output. This voltage ranges from
approximately
.1 volt (high 02 - lean mixture) to .9
volts (low 02 - rich mixture). This voltage can be
measured with a digital voltmeter having at least
10
megohms input impedance. Use of standard shop type
voltmeters will result in very inaccurate readings.
By monitoring the voltage output of the
02 sensor,
the ECM will know what fuel mixture command to
give to the Injector (lean mixture-low
02 voltage = rich
command, rich mixture-high
02 voltage = lean
command). The
02 sensor, if open, should set a Code 13. A low
voltage in the sensor circuit should set a Code 44. A
high voltage in the circuit should set a Code 45. Codes
44 and 45 could also be set
as a result of fuel system
problems. See code charts.
Throttle Position Sensor (PPS) (Fig. C4-5)
The throttle position sensor (TPS) is connected to
the throttle shaft on the throttle body. It is
a
potentiometer with one end connected to 5 volts from
the ECM and the other to ECM ground.
A third wire
is connected to the ECM to measure the voltage from
the TPS. As the throttle valve angle is changed
(accelerator pedal moved), the output of the TPS also
changes. At a closed throttle position, the output of
the TPS is low (approximately
.5 volts). As the
throttle valve opens, the output increases so that, at
wide open throttle, the output voltage should be
approximately 5 volts.
By monitoring the output voltage from the TPS,
the ECM can determine fuel delivery based on throttle
valve angle (driver demand). A
broken or loose TPS
can cause intermittent bursts of fuel from the injector,
and an unstable idle, because the ECM thinks the
throttle is moving.
A problem in any of the TPS
circuits will set either
a Code 21 or 22. Once a trouble
code is set, the ECM will use an artificial default value
for TPS, and some vehicle performance will return.
See "On-Car Service" for replacement or
adjustment of TPS.
10 THROTTLE BODY ASSEMBLY
20 THROTTLE POSITION SENSOR (TPS)
21 TPS ATTACHING SCREW
22 TPS RETAINER 55 1638-6E
Figure C1-5 Throttle Position Sensor
Vehicle Speed Sensor
The vehicle speed sensor (VSS) sends a pulsing
voltage signal to the ECM, which the ECM converts to
miles per hour. This sensor mainly controls the
operation of the TCC system. See "TCC System" for
more information.

DRIVEABILITY AND EMlSSlQNS 2.8L (VIN S) 6E3-C1-5
ECM Inputs
All of the sensors and input switches can be
diagnosed by the use of a "Scan" tool. Following is a
short description of how the sensors and switches can
be diagnosed by the use of "Scan".
The "Scan" can
also be used to compare the values for a normal
running engine with the engine you're diagnosing.
Coolant Temperature Sensor
A "Scan" tool displays engine temperature in
degrees centigrade. After
engine is started, the
temperature should rise steadily to about 90°C then
stabilize when thermostat opens. If the engine has not
been run for several hours (overnight) the coolant
temperature and MAT temperatures should read close
to each other. A fault in the coolant sensor circuit
should set a Code
14 or 15. The code charts also
contain a chart to check for sensor resistance values
relative to temperature.
MAF Sensor
A "Scan" tool reads the MAF value and displays it
in grams per second. Should read between 4-7 on a
fully warmed up idling engine. Values should change
rather quickly on acceleration, but values should
remain fairly stable at any given RPM. Most "Scan"
tools will have 2 positions for reading
MAE' sensor
values. (MAF
& Air Flow). Both values should read
the same if no Code 33 or 34 is set, but if a code is set,
the MAF values will be the default value and the Air
Flow parameter will lock in on the value to which the
ECM recognized the fault. A failure in the MAF
sensor or circuit should set a Code 33 or 34.
MAT Sensor
A "Scan" tool displays temperature of the air
entering the engine and should read close to ambient
air temperature when engine is cold, and rise as
underhood temperature increases. If the engine has
not been run for several hours (overnight) the MAT
sensor temperature and coolant temperature should
read close to each other. A failure in the MAT sensor
circuit should set
a Code 23 or 25. The code charts also
contain a chart to check for sensor resistance values
relative to temperature.
02 Sensor
The "Scan" has several positions that will indicate
the state of the exhaust gases,
O1! voltage, integrator,
and block learn. See "Scan" position information in
"Introduction," Section
"6E".
A problem in the O2 sensor circuit, or fuel system,
should set a Code 13 (open circuit), Code 44 (lean
indication), Code 45 (rich indication). Refer to
applicable chart if any of these codes
were stored in
memory.
TPS
A "Scan" tool displays throttle position in volts.
You should read
.55V f .08V, with throttle closed and
ignition on, or at idle. Voltage should increase at
a
steady rate as throttle is moved toward WOT.
The ECM has the ability to Auto-Zero the TPS
voltage if it is below about .7V (700
mV). This means
that any voltage less than
.7 volts will be determined
by the ECM to be
0% throttle. A failure in the TPS or
circuit should set a Code 21 or 22.
A "Scan" tools reading should closely match with
speedometer reading with drive wheels turning.
A
failure in the VSS circuit should set a Code 24.
PIN Switch
A "Scan" tool should read PIN when in Park, or
Neutral, and R-D, L, when in Drive or Overdrive.
This reading may vary with different makes of tools.
Refer to CHART
C-1A for PIN switch diagnosis.
NC Request Signal
"Scan" tool should indicate A/C request "ON,"
when A/C is requested and the pressure cycling switch
is closed.
Power Steering Pressure Switch
A "Scan" tool should read "OFF" normally and
"ON" with high pressure. This reading may vary with
different make of tools. Refer to CHART
C-1E for
PSPS diagnosis.
Reference Signal
A "ScanJ' tool will read this signal and is displayed
in rpm.
ON-CAR SERVICE
ELECTRONIC CONTROL MODULE (ECM)
Service of the ECM should normally consist of
either replacement of the ECM or a PROM change.
If the diagnostic
procedures call for the ECM to be
replaced, the engine calibrator (PROM) and ECM
should be checked first to see if they are the correct
parts. If they are, remove the PROM from the faulty
ECM
and install it in the new service ECM. THE
SERVICE ECM WILL NOT CONTAIN A PROM or
CALPAK. Trouble Code 51 indicates the PROM is
installed improperly or has malfunctioned. When
Code
51 is obtained, check the PROM installation for
bent pins or pins not fully seated in the socket. If it is
installed correctly and Code 51 still shows, replace the
PROM.

DRIVEABILITY AND EMISSIONS 2.8L (VIN S) 6E3-C1-7
REFERENCE END
PROM PROM CARRIER
4S 81165-6E
Figure C1-8 PROM in PROM Carrier
mnstall or Connect
1. New PROM carrier in PROM socliet.
2. CALPAK in CALPAK socket.
mmportant
Small notch of carrier shoiild he aligned with
small notch in socket. Press on PROM carrier
until it is firmly seated in the socket. Do not press
on PROM; only the carrier.
3. Access cover on ECM.
4. ECRil in passenger compartment.
5. Connectors to ECM.
b A,' I
;,* fd I
: GRASP CALPAK 1% ,/w 1' CARRIERAT
[ZJ REMOVAL TOOL
Figure C1-9 Removing CALPAK
B. If Trouble Code 51 occurs or if the "Service
Engine Soon" light is on constantly with no
codes, the PROM is not fully seated, installed
backwards, has bent pins, or is defective. If
Code
52 occurs, the CALPAK is not fully
seated, installed backwards, has bent pins, or
is defective.
If not fully seated,
press firmly on PROM
or CALPAK carrier
a, If it is necessary to remove the PROM or
CALPAK, follow instructions in steps "A"
and
"B".
@ If installed backwards, REPLACE THE
PROM. The CALPAK may be removed
and reinstalled correctly.
@ If pins bend, remove PROM or CALPAK,
straighten pins, and reinstall. If
bent pins
break or crack during
straightening,
discard PROM or CtILPAK and replace it,.
am port ant
Any time the PROM in installed backwards and the
ignition switch turned
"ON," the f'I CALPAK see figure C1-9 or refer to step 3 of
PROM and ECM replacement.
COOLANT SENSOR
NOTICE:
Care must be taken when handling
coolant sensor.
Damage to coolant sensor
will affect proper operation of the Fuel
Injection
system.
B Remove or Disconnect
1. Negative buttery cable.
2.
Electricril connector.
3. Carefully back out coolant sensor.
a ln,aIl
1. Sensor in
or Connect
engine.
2. Electrical connector.
3. Negative battery cable.
MAF SENSOR
Functional Check
Replacement of the iL'IAF xcnsor is shown in
Figure C1-10. When
replacing the MAF sensor,
1. Turn ignition on.
replace cla~llps with special hcrew type cla~rlps
2. Enter diagnostics (see Diagnostic Circuit Check (Service Part).
for procedure).
A. Code 12 should flash at least four times. (Yo MAF SENSOR POWER & BURN-OFF RELAY
other codes present). This indicates the PIIOM
and CALPAK is installed properly.
Refer to Figure C 1- 1 1 for relay location. 'rhe MAF
power relay is to the right ofthe radiator

6E3-(31-8 2.8L (VIN S) DRIVEABILITY AND EMISSIONS
( MASS AIR FLOW SENSOR
Figure C1-10 MAF Sensor Service
BRAKE BOOSTER FUEL PUMP RELAY
/ /FAN RELAY
FORWARD LAMP
/ BULKHEAD
Figure C1-I I Relays
OXYGEN SENSOR
NOTICE:
The oxygen sensor uses a permanently
attached pigtail and connector. This
pigtail should not be removed from the
oxygen sensor. Damage or removal of the
pigtail or connector could affect proper
operation of the oxygen sensor.
Important
Take care when handling the oxygen sensor. The
in-line electrical connector and louvered end must
be kept free of grease, dirt or other contaminants.
Also, avoid using cleaning solvents of any type.
Do
not drop or roughly handle the oxygen sensor.
EXHAUST CROSSOVER PIPE
Figure C1-12 0, Sensor
Remove or Disconnect
The oxygen sensor may be difficult to remove
when engine temperature is below 48°C (120°F).
Excessive force may damage threads in exhaust
manifold or exhaust pipe.
~
1. Negative battery cable.
2. Electrical connector.
The vehicle should be raised on hoist because the
0, sensor is mounted behind the exhaust Y-pipe.
3. Carefully
back out Oxygen Sensor.
Install or Connect 1 i
Important I I
A special anti-seize compound is used on the
oxygen sensor threads. The compound consists
of a
liquid graphite and glass beads. The graphite will
burn away, but the glass beads will remain, making
the sensor easier to remove.
New or service sensors will already have the
compound applied to the threads. If a sensor is
removed from an engine, and, if for any reason it is to
be reinstalled, the threads must have anti-seize
compound applied before reinstallation.
1. Coat threads of oxygen sensor with anti-seize
compound
PIN 5613695 or equivalent if necessary.
2. Sensor, and torque to 41 N-m (30 ft. Ibs.).
3. Electrical connector.
4. Negative battery cable.
Throttle Position Sensor (TPS)
a Remove or Disconnect
1 Electrical connector.
2. Two 'I'PS attaching screws and retainers.
3. Sensor.