EPA-AA-TAEB-80-6
Evaluation of Applicability of Inspection/Maintenance
Tests on a Chevrolet Citation
November 1979
by
Thomas J. Penninga
Technology Assessment and Evaluation Branch
Emission Control Technology Division
Office of Air, Noise and Radiation
U.S. Environmental Protection Agency
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Abstract
This report presents testing results which were gathered to determine
the suitability of existing I/M testing scenarios on a Chevrolet car
with a computer based emission control system. This car had a micro-
processor based three-way catalyst control system. After suitable base-
lines were established, various components were made inoperative in the
emission control system. Complete FTP, HFET, New York City Cycles, and
I/M tests were run for each vehicle condition.
This report presents the measured data taken during the tests.
Background
It is anticipated that, in the near future, electronics and computers
will control many of the vital functions of automotive operation now
regulated by mechanical means. As the Inspection/Maintenance effort is
expanded it is a prerequisite that the test procedure used by the
Inspection/Maintenance program be capable of determining equipment
failure and parameter misadjustment. With the advent of advanced elec-
tronics into automobiles, it is necessary to evaluate the suitability of
existing and proposed I/M tests to these future automobiles. To accom-
plish this evaluation, several prototype cars containing the best pro-
jected electronics of the future will be tested according to both the
Federal Test Procedures and I/M tests. The derived data should indicate
which I/M test best suits these automobiles. This report presents the
data collected on the third such automobile tested by the EPA, a 1980
Chevrolet Citation with a microprocessor controlled emission control
system.
History
The Citation is an early introduction 1980 production vehicle rented
from a local Chevrolet dealer. This particular vehicle which has a
California emission package, was delivered to EPA on May 25, 1979.
After two baseline runs, mileage accumulation began. At 1700 miles the
I/M baseline testing started.
After two baseline sequences were run, the vehicle was tested with seven
different system deactivations. Two final confirmatory baseline se-
quences were then run. The testing was completed on September 28, 1979.
Testing Procedure
In order to test the vehicle, the following test scenario was used:
a. Federal Test Procedure (FTP) 1979 procedure, non-evaporative,
no heat build.
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b. Raw HC/CO measurement, hood open, fan on, idle-neutral
(baseline only).
c. Highway Fuel Economy Test (HFET) immediately after FTP.
d. Raw HC/CO measurement, hood open, fan on, idle-neutral
(baseline only).
e. New York City Cycle (NYCC) immediately after HFET.
f. Raw HC/CO measurement, hood open, fan on, idle-neutral,
(baseline only).
g. Federal Three Mode. The dynamometer was set at 1750 Ibs.
inertia and horsepower was set at 6.5 hp at 25 mph and 11.0 hp
at 52.0 mph. The hood was open and the auxiliary cooling fan
turned on. Idle HC and CO measurements were taken in drive
and in neutral on a garage type analyzer.
h. Loaded Two Mode. The dynamometer was set a 9.0 AHP at 30 mph
with the I.W. = 1750 Ibs. The hood was open and the auxiliary
cooling fan turned on. Idle HC and CO measurements were then
taken in neutral.
i. Two Speed Idle Test with raw HC/CO garage type analyzer tested
at 2500 rpm (neutral) and idle (neutral). The hood was open
and the auxiliary cooling fan turned on.
j. Abbreviated I/M cycle with raw HC/CO garage analyzer tested at
idle (neutral momentarily accelerated to 2500 rpm (neutral),
and then tested again at idle (neutral). The hood was open
and the auxiliary cooling fan turned on.
i
k. Federal Three Mode (same as above).
1. Loaded Two Mode (same as above).
m. Two Speed Idle Test ( same as above).
n. Abbreviated I/M Cycle (same as above).
o. Prolonged Idle Cycle. With the cooling fan off and hood
closed, idle (neutral) HC and CO measurements were taken every
minute for 10 minutes on a garage type analyser (baseline
testing only).
A work sheet recording the I/M test results is shown in Attachment 1.
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-4-
Vehicle Description
The Chevrolet Citation used for this testing was a production vehicle
with a California Emission Package. Attachment 2 lists specific vehicle
parameters. The most important aspect of this automobile's emission
control system were the sensors, actuators, and microprocessor units. A
complete description of these components is given in Attachment 3.
Baseline Data
To accurately determine the effect of the various vehicle conditions, it
was necessary to have an accurate baseline determined for each con-
stituent in each mode in every test type. This baseline data is dis-
played with the configuration data.
Test Configurations
After the baseline testing and sorting out of the testing procedures,
several components of the emission control system were, one by one,
deactivated prior to vehicle testing.
a. Coolant Temperature Switch Disconnected - Test Numbers 79-8691,
79-8692, and 79-8693 were run with the Coolant Temperature dis-
connected. Because the EGO sensor does not perform properly until
it reaches temperature, the coolant sensor informs the FCC to
operate in open-loop mode until the EGO sensor temperature is
reached.
b. EGO Sensor Disconnected - Test Numbers 79-8694 and 79-8695 were
done with the exhaust gas oxygen (EGO) sensor disconnected. This
unit supplies a voltage signal to the feedback carburetor computer
based on the oxygen content of the exhaust stream. By discon-
necting the sensor the output voltage goes close to zero and the
closed loop system is deactivated. These tests were designated EGO
Sensor Disconnected.
c. Mixture Control Solenoid - Test Numbers 79-8696 and 79-8697 were
run with the mixture control solenoid disconnected. This solenoid
oscillates at a duty cycle determined by the microprocessor. The
duty cycle determines the fuel/air ratio of the intake air. With
this device deactivated the system faults to a full rich condition.
d. EGR Disconnected - Test Numbers 79-8698, 79-8699, 79-8700 and
79-8701 were run with the Exhaust Gas Recirculation Valve(EGR)
vacuum line disconnected and plugged. This device resubmits a
portion of the burned exhaust gas into the combustion chamber.
This exhaust gas lowers the peak combustion chamber temperature
resulting in reduced NOx formation. The first two tests, numbers
79-8698 and 79-8699 were void due to exhaust analysis on the
incorrect ranges.
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e. EGR Valve and Mixture Control Solenoid Disconnected - Test numbers
79-9557 and 79-9558 were run with the components in both (c) and
(d) deactivated.
f. Closed Throttle Sensor Disconnected - Test Numbers 79-9559 and
79-9560 were run with the Closed Throttle Sensor electrically
disconnected. This device informs the microprocessor that the
carburetor is closed. Disconnecting the device electrically gives a
fixed throttle input to the microprocessor.
g. EGO Sensor Short Circuited - Test Numbers 79-9561 and 79-9562 were
tested with the Exhaust Oxygen Sensor (EGO) disconnected. This
shorting of the sensors guaranteed a zero voltage input and a full
rich duty cycle.
Test Results .
The test results are given in several attachments.
a. The FTP, HWFET, and NYCC with the corresponding raw HC/CO
readings are given for baseline configuration studies in
Attachment 4. The HC, CO, CO,, and NOx readings are in gms/
mile while the fuel economy is in miles per gallon. The raw
HC readings are in ppm/hexane and the raw CO readings are in
percent.
b. Attachment 5 presents the standard I/M test data. As each
test were run twice, two sets of values are given.
c. Attachment 6 also presents the Prolonged Idle Cycle Data.
List of Attachments
Attachment 1 I/M Test Result Work Sheet
Attachment 2 Test Vehicle Description
Attachment 3 GM C-4 Description
Attachment 4 Dilute and I/M Sample Data
Attachment 5 I/M Sample Data
Attachment 6 I/M Prolonged Idle Test Data
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Attachment 1
I/M Prototype Testing: Raw Exhaust EC, CO Data Sheet
Technicians: Location: Date:
Vehicle: Baseline Other:
HC CO COMMENTS
AFTER FTP
Hood open fan on
Transmission-neutral
(Baseline only)
AFTER HWFET
Hood open fan on
Transmission-neutral
(Baseline only)
AFTER NYCC
Hood open fan on
Transmission-Neutral
(Baseline only)
FEDERAL 3 MODE
Hood open, fan on
Set 8.8 on thumbwheel
52 MPH-max 3 min. .
Set 5.8 IHP @ 25 MPH
with Pendent
25 MPH-max 3 min.
Idle (Drive)
Idle (Neutral)
LOADED 2 MODE
Hood open, fan on
Set dyno at
Thumbwheel or 7.9
on Pendent at 30 MPH
30 MPH
Idle (Neutral)
TWO SPEED IDLE CYCLE
Hood open fan on
Idle (Neutral)
Increase Idle speed to 2500
+ 100 RPM
Idle (Neutral)
ABBREVIATED I/M IDLE CYCLE
Hood open fan on
Idle (N)
Momentary rev. to 2500 RPM
Idle (N)
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HC
CO
COMMENTS
REPEAT
REPEAT
FEDERAL THREE MODE
Hood open, fan on
Set 8.8 on Thumbwheel
52 MPH-Max 3 min.
Set 5.8 IHPQ25 MPH
with Pendent
25 MTH-Max 3 min.
Idle (Drive)
Idle (Neutral)
LOADED TWO MODE
Hood open, fan on
Set dyno at
Thumbwheel or 7.9
on Pendent at 30 MPH
30 MPH
Idle (Neutral)
TWO SPEED IDLE CYCLE
Hood open fan on
Idle (Neutral)
Increase Idle Speed to
2500 + 100 RPM
Idle (Neutral)
ABBREVIATED I/M CYCLE
Hood open fan on
Idle (Neutral)
Momentary rev. to 2500 RPM
Idle (Neutral)
PROLONGED IDLE CYCLE
Hood closed, fan off
Idle (Neutral) Minutes
(Baseline only) 0
1
2
3
4
5
6
7
8
9
10
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Attachment 2
-8-
Test Vehicle Description
Model/Year
Make
Emission Control System
Engine Configuration
Engine Type
Bore x Stroke
Displacement
Rated Horsepower
Transmission
Axle Ratio
Chassis Type
Tire Size
Inertia Weight
VIN
40% Fuel Tank Volume
AHP
Engine Family
Evap Family
N/V Ratio
Fuel Type
Compression Ratio
Model Designation
1980
Chevrolet Citation
EGR, Pulse-Air, 3-Way, Closed Loop
1-4
Otto Spark
101.6mm x 76.2mm
2500 cc
90
A-3
2.53
Sedan
P 185 x 80 R13
2750 Ibs.
1 X 685 A W 140457
5.6 gallons
7.3
02X2NC
0 B6-2
35.7
Unleaded-Ind H 0
8.2
IXX11
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6E-18 EMISSION CONTROL SYSTEMS
-9-
Attachmeast
8. Re-connect vacuum hoses per vacuum hose
schematics.
CaSofoirnia
1. Allow engine to cool off to a temperature below 80°F.
(26°C.)- This may require not starting the engine for a period
of 12 hours. If this is not possible, refer to off-car functional
checks of individual components in this section.
2. Disconnect vacuum hose at distributor and connect
a band vacuum pump to the distributor spark vacuum unit
and apply 15 inches of mercury vacuum. Observe vacuum
reading for 20 seconds. If vacuum drops more than one inch,
replace vacuum unit. -,. .-: ,. . -;:
3. "Tee" a vacuum gage into the vacuum retard hose
at the distributor spark vacuum unit.
4. Start engine and observe vacuum 'reading. With
carburetor on high step of fast idle cam, vacuum should be
within one inch of manifold vacuum. If not, trace back along
the vacuum source until the vacuum leak or plugged
condition is located. Correct as necessary. '
5. With engine at fast idle allow vacuum reading to
stabilize. Turn off the ignition and observe the vacuum gage.
Vacuum reading should not drop immediately, but
should drop slowly (taking about 24 to 36 seconds to
go from D 5 to 5 inches).
6. If the vacuum drops too fast, the VDV is defective «j
or there is a leak in the distributor vacuum advance unit.
If the vacuum drops too slowly, the VDV is defective. ^
7. Allow engine to warm up until coolant temperature 4
is above 160°F (71°C). With engine at fast idle allow vacuum ~
reading to stabilize. Turn ignition off and observe vacuum
reading. Vacuum should drop immediately. If vacuum does
not drop immediately, either the vacuum hoses between the
DS-TVS and VDV are plugged or the DS-TVS is defective;
repair as required.
8. With engine at normal operating temperature and;;
slow idle, check for vacuum at hose to distributor. There
should be less than 1 inch of mercury vacuum. If vacuum -;
is present, check idle speed and reset as necessary. If vacuum
is still present, check DS-TVS. Replace DS-TVS if
necessary.
9. Open throttle slightly and observe an increase in
vacuum at the distributor. If vacuum is not present at fast
idle, check for plugged or leaking vacuum hoses. Replace
as necessary.
10. Re-connect vacuum hoses per vacuum hose
schematics.
The C-4 is a system that controls emissions by close
regulation of the air-fuel ratio and by the use of a three way
Catalytic Converter which lowers the level of oxides of
Nitrogen, Hydrocarbons and Carbon Monoxide.
The essential components are an exhaust gas Oxygen
Sensor (OS), an Electronic Control Module, (ECM) an
electronically controlled air-fuel ratio carburetor and a a
three way Catalytic Converter (ORC). See Figures 6E-31.
thru 6E-35. ;
(Figure SE-31) ' - : :; -
i .
The oxygen sensor used in the C-4 system consists of
a closed end Zirconia sensor placed in the engine exhaust
gas stream. The sensor generates a voltage which varies with
the oxygen content in the exhaust gas stream. As oxygen
content increases, (which indicates a lean mixture) voltage
falls, and as oxygen content decreases, (indicating a rich
mixture) voltage rises.
NOTICE: Oxygen sensor used for 1980 engines has a
permanently attached wiring pig-tail and connector.
This pig-tail should not be removed from the oxygen
sensor. (Figure 6E-31). Damage to pig-tail or connection
could affect proper operation of the oxvopn sen«or
LEAN MIXTURE
O_ IN EXHAUST
GAS
CARBURETOR CONTROL
"LEANS" MIXTURE
LOW SENSOR
VOLTAGE
ELECTRONIC CONTROL
UNIT ENERGIZES
CARBURETOR SOLENOID
ELECTRONIC CONTROL
UNIT DE-ENERGIES
CARBURETOR SOLENOID
HIGH SENSOR
VOLTAGE
CARBURETOR CONTROL
ENRICHENS MIXTURE
LESS O2IN
EXHAUST GAS
5525
Figure 6E-25 Cycle of Operation
ElECTOOWDC
(Figure 8E-33)
The Electronic Control Module (ECM) monitors the
voltage output of the oxygen sensor along with information
from other input signals to generate a control signal to the
carburetor solenoid. (Figure 6E-25) The control signal is
continually cycling the solenoid between ON (lean
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EMISSION CONTROL SYSTEMS 6E-19
f*
TO ENGINE
COMPARTMENT WIRING
ECM
CONNECTORS
PANEL
FUSE
DIAGNOSTIC GROUND
(TEST LEAD)
DIAGNOSTIC BATTERY
LEAD (FOR ECM MEMORY)
PLUG INTO CAVITY
MARKED IGN NO. 1 (NAT)
' CHECK ENGINE" GAGE CLUSTER ASM
LAMP
VACUUM
SWITCHES
MIXTURE CONTROL
SOLENOID CONNECTOR
THREE WAY
CATALYTIC CONVERTER
ENGINE COOLANT
TEMPERATURE SENSOR
OXYGEN SENSOR
7451
Figure 6E-26 Computer Controlled Catalytic Converter System - Typical
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6E-20 EMISSION CONTROL SYSTEMS
-11-
LEAN LIMIT SIGNAL (2.8 LITRE V-6)
THROTTLE MODE (2.8 LITRE V-6)
COOLANT TEMPERATURE
ENGINE SPEED
VACUUM MODE (2.5 LITRE L-4)
I CARBURETOR
| SOLENOID SIGNAL
PULSAIR SOLENOID SIGNAL
I :~~~ ~
ELECTRONIC
CONTROL MODULE
SYSTEM MALFUNCTION
LAMP
I_
12 VOLT POWER
7450
*'
1
Figure 6E-27 Computer Controlled Catalytic Converter System Schematic
MIXTURE CONTROL
SOLENOID TEST LEAD
MIXTURE
CONTROL -
SOLENOID
VACUUM SWITCHES
(THROTTLE POSITION)
SEE I.P. WIRING
OXYGEN
SENSOR
ENGINE COOLANT
TEMPERATURE SENSOR
7452
Figure 6E-28 Wiring System - L4
command) and OFF (rich command). When the solenoid
is ON (energized) the solenoid pulls down a metering rod
which reduces fuel flow. When the solenoid is OFF (de-
energized) the spring-loaded metering rod returns to the up
position, increasing fuel flow. The amount of ON time
relative to OFF time is a function of the input voltage from
the oxygen sensor.
To maintain good idle and driveability under all
condition other input signals are used to modify the ECM
output signal. (Figure 6E-27) These input signals are
supplied by Engine Temperature Sensor, Vacuum Control
Switch(s), Throttle Position Switch, and Distributor
(Engine Speed).
ENGINE TEMPERATURE SENSOR
The Engine Temperature Sensor is a thermistor which
inputs engine coolant temperature information to the ECM.
This information is used to modify the ECM output signal
to adjust for cold engine condition and maintain good
. driveability during warm up.
VACUUM CONTROL SWITCHES
(FIGURE 6E-34)
2.5 Litre L4 Engine - The vacuum control switches
monitor the vacuum signal enabling the ECM to recognize
closed throttle (idle) or open throttle operation (also see
Throttle Position Sensor, 2.8 Litre V6).
2.8 Litre V6 Engine - The vacuum control switch (Lean
Authority Limiter) monitors heated carburetor inlet air
1
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EMISSION CCNTROL SYSTEMS 6E>21 -
MIXTURE
CONTROL
SOLENOID
THROTTLE1
POSITION
SWITCH
,LEAN AUTHORITY
SWITCH
\^
&>SEE I.P. WIRING
FWD
PULSAIR
SOLENOID
B
CLIP
HARNESS
FWD
:OOLANT
TEMP. SENSOR
OXYGEN
SENSOR
"
7455
Figure 6E-29 Wiring System - V6
ELECTRONIC
CONTROL
MODULE
FUSE BLOCK
"CHECK
ENGINE
LIGHT
DIAGNOSTIC GROUND
(TEST LEAD) DIAGNOSTIC BATTERY
LEAD (FOR ECU MEMORY)
PLUG INTO CAVITY
MARKEDIGN#1 (NAT).
INSTRUMENT
CLUSTER ASM.
7660
Figure 6E-30 IP Wiring System
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E-22 EMISSION CONTROL SYSTEMS
-13-
ELECTRONIC
CONTROL MODULE
INSTRUMENT
PANEL
7453
Figure 6E-31 Oxygen Sensor
Figure 6E-33 Electronic Control Module (ECM)
EXHAUST
MANIFOLD
/
CONVERTER
ASSEMBLY
V-6 ENGINE
7454
L-4 THROTTLE
POSITION SWITCHES
V-6 LEAN AUTHORITY
LIMITER SWITCH
7456
1
Figure 6E-32 Oxygen Sensor Mounting
.Figure 6E-34 Vacuum Control Switch
through an air cleaner TVS and prevents the ECM from
driving the carburetor too lean for good driveability during
cold operation.
Throttle Position Sensor (2.8 Litre V6
Engine) (Figure 6E-36)
The Throttle Position Sensor (2.8 Litre V6) and
Vacuum Control Switch (2.5 Litre L4) supply throttle
position information to the ECM. The ECM memory stores
an average of operating conditions with ideal air fuel ratio
for those operating conditions. When the ECM receives a
signal that indicates throttle position change it immediately
shifts to the last "remembered" set of operating conditions
that resulted in ideal air-fuel ratio control. During normal
operation the memory is continually being updated.
DISTRIBUTOR (ENGINE SPEED)
To assist in engine start-up the ECM at engine speeds
under 200 RPM sends no signal to the carburetor mixture'
.control solenoid.
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EMISSION CO JTROL SYSTEMS 6E-23
7199
Figure 6E-35 Coolant Temperature Sensor - L4
7600
Figure 6E-36 Throttle Position Sensor-V6
PULSAIR
SOLENOID CONNECTOR TOC-4
- WIRING HARNESS
7458
-Figure 6E-37 Pulsair Solenoid - V6
CARBURETOR
The Model E2SE carburetor used with the C-4 System
is a controlled air-fuel ratio carburetor of a two barrel, two
stage down draft design with the primary bore smaller in
size than the secondary bore. Air-fuel ratio control is
accomplished with a solenoid controlled on/off fuel valve
which supplements a preset flow of fuel supplying the idle
and main metering systems. The solenoid on/off cycle is
controlled by a 12 volt signal from the ECM. The solenoid
also controls the amount of air bled into the idle system. The
air bleed valve and fuel control valve work together such
that the fuel valve is closed when the air bleed valve is open,
resulting in a leaner air-fuel mixture. Air-fuel mixture
enrichment occurs when the fuel valve is open and air bleed
valve closed.
THREE WAY CATALYTIC CONVERTER
The Three Way Catalytic Converter reduces oxides of
nitrogen while improving the characteristics of inducing
oxidation of Hydrocarbons and Carbon Monoxide. To
maintain high conversion efficiency it is necessary to closely
control the air fuel ratio.
DIAGNOSTIC SYSTEM
The Computer Controlled Catalytic Converter (C-4)
System should be considered as a possible trouble source of
engine performance, fuel economy and exhaust emission
complaints. A built-in diagnostic system catches problems
most likely to occur.
Before suspecting the C-4 system or any of its
components as a trouble source, check ignition system
including distributor, timing, spark plugs and wires. Check
air cleaner, Evaporative Emissions Systems, EFE System,
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SE-24 EMISSION COWTROLSYSTEMS
-15-
PCV System, EGR valve and engine compression. Also
inspect intake manifold, vacuum hoses, and hose
connections for leaks, and carburetor mounting bolts.
The following symptoms could indicate a possible
problem with the C-4 system.
1. Detonation
2. Stalls or rough idle - cold
3. Stalls or rough idle - hot
4. Missing
5. Hesitation
6. Surges
7. Sluggish or spongy ..-..:.
8. Poor gasoline mileage '/..-.
9. Hard starting.-cold :;:'...
10. Hard starting - hot -
11. Objectionable exhaust odor
>"12. Cuts out" 3 ,-. '7 A".. ' ' W isaft^ "
The self diagnostic system lights a "CHECK
ENGINE" light on the instrument panel when a
malfunction occurs. By grounding a 'TROUBLE CODE*
test lead (white/black wire with green connector) under the
instrument panel (See Figure 6E-38) the "CHECK
ENGINE" light will flash a numerical code if the diagnostic
system has detected a fault.
As a bulb and system check, the light will come "ON"
when the ignition is turned "ON" with the engine stopped.
The "Check Engine" light will remain "ON* approximately
4 seconds after the engine is started. If the "TROUBLE
CODE" test lead is grounded with ignition switch "ON"
and engine stopped, the light will flash a code "12" which
indicates the diagnostic system is working. This consists
of one flash followed by a pause and then two more
flashes. After a longer pause the code will be repeated two
more times. The cycle will then repeat itself until the engine
is started or the ignition turned off. If the light does not flash
the code "12" refer to Figure 6E-42, "Diagnostic System
Check*.
If the "TROUBLE CODE" test lead is grounded with
the engine running and a fault has been detected by the
system, the trouble code will flash three times. If more than
one fault has been detected, its code will be flashed three
times after the first code set. The series will then repeat itself.
. A trouble code indicates a problem with a given circuit,
for example, code 14 indicates a problem in the coolant
sensor circuit. This includes the coolant sensor, harness and
Electronic Control Module (ECM). The procedure for
finding which of the three it is, can be found in Diagnosis
chart #14. The same applies to all other trouble codes.
Since the self diagnostics do not include all possible
faults, the absence of a code does not mean there is no
problem with the system. To determine this, a system
performance check is necessary. See Figure Figure 6E-43,
"System Performance Check"; It is made when the
"CHECK ENGINE" light does not indicate a problem but
the C-4 system is suspected because no other reason can be
found for a complaint. A dwell meter, ohmmeter, test light,
voltmeter, tachometer, vacuum gauge and jumper wires are
required to diagnose the system. . .
The dwell meter, set on the 6 cylinder position and
connected to a lead from the mixture control (M/C)
a
8
DIAGNOSTIC
GROUND
(TEST LEAD
WHITE/BLACK WIRE)
FUSE PANEL
DIAGNOSTIC
BATTERY LEAD
(FOR ECM MEMORY
ORANGE WIRE)
FUSE PANEL
DIAGNOSTIC GROUND
(TEST LEAD-WHITE/BLACK WIRE)
DIAGNOSTIC BATTERY LEAD
(FOR ECM MEMORY-ORANGE WIRE)
2.8L-V6
2.5L-L4
7459
Figure 6E-38 C-4 System Diagnostic Test Leads
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EMISSION CONTROL SYSTEMS 6E-25
solenoid in the carburetor, is used to measure the output of
the ECM.
NOTICE: When the dwell meter is connected, do not
allow the lead to touch ground. This includes hoses
because they are conductive.
On a normal operating engine, the dwell at both idle
and part throttle reads somewhere between 10° and 50° and
will be varying. "Varying" means the needle continually
moves up and down the scale. The amount it moves does
not matter, only the fact that it does move. This is called
closed loop operation, meaning the dwell is being varied by
the signal sent to the ECM by an oxygen sensor in the
exhaust pipe. Under certain operating conditions such as
wide open throttle (WOT) or a cold engine, the dwell will
be a fixed value and the needle will be steady. This is called
open loop, meaning the oxygen sensor has no effect on the
dwell.
Normally, checks are made on a warm engine (upper
radiator hose hot).
Trouble Code Memory
When a fault develops in the system, the "check
engine" light will come on and a trouble code will be set in
the memory of the ECM. However, if the fault is
intermittent, the "CHECK ENGINE" light will go out
when the trouble goes away, but the trouble code will remain
in the memory of the ECM.
Temporary vs Long Term Memory
The ECM as it comes on the car has a temporary
memory. That is, the trouble code will be lost as soon as the
ignition switch is turned off. Some trouble codes will not be
recorded in the ECM until the car has been operated for
about 5 minutes at part throttle. For this reason and in order
to remember intermittent problems, a long term memory is
desirable. Then codes would not be lost when the ignition
switch is turned off.
The ECM can be made to have long term memory by
connecting the orange connector/lead from terminal "S" of
the ECM to fuse block cavity marked "GAUGES. (See
Figure 6E-38).
It is not normally connected because it causes a small
current drain even when the ignition switch is turned off.
This could cause a run down battery if the car were not run
for a long time.
If the long term memory has been activated, the
orange connector/lead must be disconnected when
repairs are completed.
When the "CHECK ENGINE" light is not "ON" with
the engine running, but a trouble code can be obtained, the
diagnosis charts cannot be used because the system is
operating properly at the time. All that can be done is a
physical inspection of the circuit indicated by the trouble
code. It should be checked for poor connections, frayed
wires, etc.
THROTTLE POSITION SWITCHES
The 2.5L L4, VIN Code 5 engine uses two vacuum
switches to inform the ECM of closed throttle vs open
throttle operation. The 2.8L V6 VIN Code 7 engine uses a
throttle position sensor to signal wide open throttle as well
as idle vs part throttle.
The two systems have to be diagnosed differently, So
where necessary, it will be so indicated in diagnostic
procedures.
ELECTRONIC CONTROL MODULE
(ECM)
ECMs have a calibration unit called a PROM
(Programable Read Only Memory) which contains the
specific instructions for a given application. It is a
replaceable assembly which plugs into a socket and requires
a special tool for removal and replacement.
The PROM and the socket each have a-mark on one
end that must be aligned when installing and care must be
used to not bend the twenty, pin contacts on the PROM.
Trouble code 51 indicates the PROM is installed
improperly or is defective. When code 51 is obtained on a
factory installed ECM, the ECM should be replaced. On a
service unit the PROM installation should be checked for
bent pins or being installed 180" rotated.
Service ECMs will come without PROMs, so the
proper PROM will also have to be ordered and installed.
Connecting a Tachometer
The lead from the distributor tachometer terminal to
the ECM has a filter in series with it. The tachometer must
be connected to the distributor side only. (Figure 6E-39).
-------
6E-26 EMISSION CONTROL SYSTEMS
-17-
L-4 TACHOMETER
CONNECTOR
V-6 TACHOMETER
CONNECTION
7460
Figure 6E-39 Tachometer Test Leads
TROUBLE (FAULT) CODES
The trouble codes indicate faults or problem areas listed below.
Refer to the Diagnostic Chart with same numerical trouble code (see
Figure 6E-44 through 6E-62).
NOTICE: The system performance check (Figure 6E-43) should be
performed after any repairs to this system have been made and then long
term memory cleared. If long term memory is left connected battery could
be run down.
Trouble Code
Problem Area - Refer to Corresponding Diagnostic Chart
12
13
13 & 43
14
15
21
21 & 22
22
23
44
45
51
No tachometer signal to the ECM
Oxygen sensor circuit. The engine has to operate for about 5 minutes
at part throttle before this code will show. ;
Same time - See Code 43. (Code 43 - 2.8L V6 only)
Shorted coolant sensor circuit. The engine has to run 2 minutes
before this code will show.
Open coolant sensor circuit. The engine has to operate- for about 5
minutes at part throttle before this code will show.
Throttle position sensor circuit (2.8L V6)
(At same time) grounded WOT switch circuit. (2.5L L4)
Grounded closed throttle or WOT switch circuit. (2.5L L4)
Carburetor solenoid circuit.
(2.8L V6)
Lean Oxygen Sensor
Rich Oxygen Sensor
On Service Unit, check calibration unit (PROM) installation.
On factory installed unit, replace ECM.
-------
.HI mi .mnililii li-TV. Hi,,, mil
-18-
EMISSION COrv FROL SYSTEMS 6E-2J
54
52, 53
55
55
Faulty carburetor solenoid and/or ECM.
Replace ECM.
Faulty throttle position sensor (2.8L V6) or ECM
Replace ECM (2.5L L-4).
EXPLANATION OF ABBREVIATIONS
C-4 - Computer Controlled Catalytic Converter
PROM - Calibration Unit
ECM - Electronic Control Module
OEM - Original Equipment Manufacture
WOT - Wide Open Throttle
TPS - Throttle Position Sensor
M/C SOLENOID - Mixture Control Solenoid
BAT-f - Battery Positive Terminal
-i-'
:-il:-'
:/'.
-------
Dilute Sampling Testing
.c
01
6
o
JJ Date
7-17-79
8-1-79
8-8-79
8-9-79
8-14-79
8-15-79
8-23-79
9-6-79
9-13-79
9-19-79
9-20-79
2 9-28-79
FTP (gms/mile)
Test Numbers
79-8686,87,88
79-8689,90
79-8691,92,93
78-8694,95
79-8696,97
79-8698,99
79-8700,8701
79-9557,58
79-9559,60
79-9561,62
79-9563,64
79-9565,66
HC
.251
.195
.225
.295
2.361
.176
.181
2.544
.202
2.073
.190
.178
CO
3.08
3.33
5.18
6.85
111.24
2.20
2.78
120.98
4.21
95.62
3.38
2.59
co2
392
389
378
374
282
383
378
287
393
304
360
406
NOx
.53
.52
.69
.64
.06
1.14
1.29
.17
.45
.13
.43
.79
F.E.
22.3
22.5
22.9
23.0
19.1
22.9
23.2
18.3
22.2
19.2
24.2
21.6
Raw (ppm/%)
HC
5
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
CO
0
.012
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
.013
HC
.008
.013
.011
.028
1.184
VOID
.011
1.294
.010
1.062
.010
.010
HWFET (gms/mile)
CO
.01
.063
.07
.574
68.44
VOID
.069
72.7
.025
48.73
.032
.080
co2
266
259
258
254
197.5
VOID
257.5
200.4
258.4
213.5
242.6
261.8
NOx
.43
.459
.41
1.164
.054
VOID
1.738
.167
.457
.064
.350
. .488
F.E.
33.3
34.2
34.4
34.8
28.7
VOID
34.4
27.8
34.3
30.2
36.5
33.9
Comments
Baseline
Baseline
Coolant Temp. Switch Dis:
EGO Sensor Disconnected
Mixture Control Solenoid
EGR Disconnected Void-Wrong
EGR Disconnected
Rang'
EGR Disc, and Mixture Solenoid u
Closed Throttle Sensor Disc.
EGO Sensor Short Circuited
Baseline
Baseline
All Raw HC Readings in ppm Hexane.
All Raw CO Readings in percent.
-------
Dilute Sampling Testing
Following HFET
.Raw (ppm/%)
Date
7-17-79
3-1-79
8-8-79
8-9-79
8-14-79
8-15-79
8-23-79
9-6-79
9-13-79
9-19-79
9-20-79
9-28-79
Test Numbers
79-8686
79-8689
79-8691
79-8694
78-8696
79-8698
79-8700
79-9557
79-9559
79-9561
79-9563
79-9565
,87,88
,90
,92,93
,95
,97
,99
,8701
,58
,60
,62
,64
,66
HC
8
0
N/A
N/A
N/A
N/A
N/A
, N/A
N/A
N/A
N/A
0
CO
.025
.006
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
.015
HC
.280
.217
.093
.317
4.303
.16
.107
4.289
.175
3.834
.151
.271
NYCC (gms/raile)
CO
8.565
5.869
2.764
10.086
215.3
4.07
4.08
217.86
5.492
170.1
3.984
8.881
co2
722.3
752.5
748.7
700.3
574.6
829.7
740.6
551.8
754.9
596.2
711.9
827.5
NOx
.415
.598
.755
1.062
.107
.710
.983
.157
.551
.055
.565
1.287
F.E.
12.0
11.6
11.8
12.4
9.6
12.6
11.9
9.8
11.6
10.1
12.3
10.5
Raw (ppm/%)
HC
8
0
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0
CO
.025
.010
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
.010
All Raw HC Readings in ppm Hexane.
All Raw CO Readings in percent.
Comments
Baseline
Baseline
Coolant Temperature Switch Disconnected
EGO Sensor Disconnected
Mixture Control Solenoid
EGR Disconnected Void-Wrong Ranges
EGR Disconnected
EGR Disconnected and Mixture Solenoid Disconnected
Closed Throttle Sensor Disconnected
EGO Sensor Short Circuited
Baseline
Baseline
-------
I
(J
I/M Cycle Testing
Federal Three Mode
Date
7-17-79
8-1-79
8-8-79
8-9-79
8-14-79
8-15-79
8-23-79
9-6-79
9-13-79
9-19-79
9-20-79
9-28-79
Test fs
79-8686
79-8689
79-8691
79-8694
79-8696
79-8698
79-8700
79-9558
79-9559
79-9561
79-9563
79-9565
,87,88
,90
,92,93
,95
,97
,99
,01
,57
,60
,62
,64
,66
EC/CO
52
10/.02
5/.012
0/.012
10/.011
150/6.6
18/.04
10/.02
140/6.8
19/.02
150/4.8
10/.018
0/.012
HC/CO
raph
8/.025
0/.010
0/.010
2/.015
162/6.7
18/.022
5/.045
159/6.6
10/.011
196/4.9
20/.010
0/.015
HC/CO
HC/CO
25 mph
10/.02
2/.010
0/.010
4/.001
172/6.8
14/.022
10/.015
170/6.9
29/.015
182/4.4
10/.012
0/.020
8/.025
0/.009
0/.009
0/.010
183/7.5
13/.019
2/.03
188/6.9
8/.009
208/4.6
17/.010
0/.018
HC/CO
HC/CO
Idle (Drive)
8/.02
2/.010
0/0
I/. Oil
159/7.5
13/.010
10/.01
172/7.6
29/.012
172/5.95
10/.012
0/.012
8/.025
0/.003
0/0
0/.009
170/7.5
13/.006
2/.01
173/7.6
7/.007
190/4.7
17/.07
11. 015
HC/CO
HC/CO
Idle (Neutral)
8/
3/
0/0
o/
152/7
137
10/
154/7
307
160/5
117
I/
.02
.010
.010
.6
.007
.013
.2
.010
.5
.011
.010
10/.025
0/.005
0/0
0/.010
158/7.2
13/.010
2/.012
155/7.2
9/.010
180/4.4
18/.008
0/.012
All HC readings in ppm (Hexane).
All CO readings in percent.
Loadedy.Two Mode
HC/CO
HC/CO
30 mph
107
37
O/
I/
185/6
157
57
170/6
35 /
210/5
137
I/
.025
.010
.008
.010
.9
.025
.05
.8
.010
.2
.012
.012
87
O/
O/
I/
182/7
137
27
180/6
O/
213/5
187
O/
.025
.010
.008
.018
.1
.031
.043
.7
.016
.2
.010
.012
HC/CO
HC/CO
Idle (Neutral)
87
37
0/0
I/
151/7
157
27
152/7
. 357
165/5
127
O/
.025
.010
.011
.5
.012
.01
.4
.009
.8
.010
.011
87
O/
O/
I/
152/7
12/
57
158/7
O/
180/5
187
O/
.02
.010
.001
.012
.3
.010
.020
.4
.013
.45
.008
.005
-------
I/M Cycle Testing
Two Speed Idle Cycle
Abbreviated I/M Cycle
Date
7-17-79
8-1-79
8-8-79
8-9-79
8-14-79
8-15-79
8-23-79
9-6-79
9-13-79
9-19-79
9-20-79
9-28-79
Test its
79-8686,87,88
79-8689,90
79-8691,92,93
79-8694,95
79-8696,97
79-8698,99
79-8700,01
79-9558,57
79-9559,60
79-9561,62
79-9563,64
79-9565,66
HC/CO
HC/CO
Idle (Neutral)
8/.025
.3/.010
0/0
I/. Oil
152/7.3
15/.012
2/.01
155/7.3
38/.003
168/5.6
157.010
0/.010
8/.02
0/.010
I/. 003
2/.013
153/7.2
12/.010
2/.01
162/7.25
0/.012
182/5.4
18/.008
0/.012
HC/CO
2500
8/.025
7/.010
0/.008
5/.012
120/4.6
20/.015
5/.009
83/2.9
47/.001
110/2.0
17/.010
I/. 013
HC/CO
rpm
10/.025
0/.010
0/.010
4/.017
118/4.0
15/.012
3/.012
76/2.2
I/. 012
126/2.3
20/.009
2/.013
HC/CO
HC/CO
Idle (Neutral)
10/.025
4/.010
0/.002
0/.011
150/7.4
18/.012
2/.08
149/6.9
48/0.0
168/5.5
15/.010
0/.010
8/.02
0/.010
I/. 003
3/.013
157/7.3
137.011
3/.01
157/6.9
0/.010
181/5.3
20/.009
0/.010
HC/CO
HC/CO
Idle (Neutral)
8/.025
5/.009
0/.002
0/.012
152/7.3
19/.012
2/.008
152/6.9
3/.01
170/5.5
167.010
I/. 012
87.02
0/.010
0/0
I/. 013
158/7.2
147.012
3/.01
160/6.9
0/.010
182/5.3
20/.008
0/.012
HC/CO
HC/CO
Idle (Neutral)
10/.025
4/.010
0/.001
0/.011
160/7.2
18/.01
2/.008
160/6.85
6/.011
181/5.95
187.010
2/.019
10/.025
0/.010
0/0
0/.012
158/7.0
16/.011
3/.012
164/6.8
0/.010
190/5.4
20/.008
0/.012
All HC readings in ppra (Hexane).
All CO readings in percent.
* HC background final =6.2 ppm.
Comments
Baseline
Baseline
Coolant Temp. Switch Disc.
EGO Sensor Disconnected
Mixture Control Solenoid
EGR Disc. Void-Wrong Ranges
EGR Disconnected
EGR Disc, and Mix. Solenoid Disc
Closed Throttle Sensor Disc.
EGR Sensor Short Circuited ^
Baseline if>
Baseline
3*
a
re
3
-------
S Date
7-17-79
8-1-79
9-20-79
9-28-79
Test Number
8686,87,88
8689,90
Initial 1 min.
2 min.
3 min.
Prolonged Idle Cycle (HC/CO in ppm hexane/%)
4 min. 5 min. 6 min. 7 min. 8 min. 9 min.
10 min. Comments
10/;025
2/.012
20/.007
0/.016
8/.02
5/.012
20/.007
0/.013
8/.02
10/.012
21/.008
I/. 013
8/.02
12/.013
25/.008
0/.014
10/.025
12/.011
23/. 008
0/.021
10/. 025
17/.011
26/.008
07.017
107.025
177.011
297.008
07.018
10/.025
20/.012
29/.008
0/.016
107. 025
227.010
. 21/.009
07.017
10/.025
22/.010
32/.009
07.014
10/.025
247.010
36/.009
0/.014
Baseline
Baseline - **
Baseline*
* BKGD HC drifted from 0 ppm to 35 ppm.
** BKGD HC drifted from 0 ppm to 25 ppm.
All HC readings in ppm hexane.
All CO readings in percent CO.
------- |