catalytic converter DODGE RAM 2003 Service Repair Manual

lower inside sealing seat for nicks, cracks, paint, dirt
and solder residue. Inspect the radiator-to- reserve/
overflow tank hose for internal obstructions. Insert a
wire through the hose to be sure it is not obstructed.
Inspect the cams on the outside of the filler neck.
If the cams are damaged, seating of the pressure cap
valve and tester seal will be affected.
Attach pressure tester (7700 or an equivalent) to
radiator filler neck.
Operate the tester pump to apply 103.4 kPa (15
psi) pressure to the system. If the hoses enlarge
excessively or bulges while testing, replace as neces-
sary. Observe the gauge pointer and determine the
condition of the cooling system according to following
criteria:
Holds Steady:If the pointer remains steady for
two minutes, serious coolant leaks are not present in
system. However, there could be an internal leak
that does not appear with normal system test pres-
sure. If it is certain that coolant is being lost and
leaks cannot be detected, inspect for interior leakage
or perform Internal Leakage Test. Refer to INTER-
NAL LEAKAGE INSPECTION.
Drops Slowly:Indicates a small leak or seepage
is occurring. Examine all of the connections for seep-
age or slight leakage with a flashlight. Inspect the
radiator, hoses, gasket edges and heater. Seal the
small leak holes with a Sealer Lubricant (or equiva-
lent). Repair the leak holes and inspect the system
again with pressure applied.Drops Quickly:Indicates that serious leakage is
occurring. Examine the system for external leakage.
If leaks are not visible, inspect for internal leakage.
Large radiator leak holes should be repaired by a
reputable radiator repair shop.
INTERNAL LEAKAGE INSPECTION
Remove the engine oil pan drain plug and drain a
small amount of engine oil. If coolant is present in
the pan, it will drain first because it is heavier than
oil. An alternative method is to operate engine for a
short period to churn the oil. After this is done,
remove the engine dipstick and inspect for water
globules. Also inspect the transmission dipstick for
water globules and transmission fluid cooler for leak-
age.
WARNING: WITH RADIATOR PRESSURE TESTER
TOOL INSTALLED ON RADIATOR, DO NOT ALLOW
PRESSURE TO EXCEED 145 kPa (21 PSI). PRES-
SURE WILL BUILD UP QUICKLY IF A COMBUSTION
LEAK IS PRESENT. TO RELEASE PRESSURE,
ROCK TESTER FROM SIDE TO SIDE. WHEN
REMOVING TESTER, DO NOT TURN TESTER MORE
THAN 1/2 TURN IF SYSTEM IS UNDER PRESSURE.
Operate the engine without the pressure cap on
the radiator until the thermostat opens. Attach a
Pressure Tester to the filler neck. If pressure builds
up quickly it indicates a combustion leak exists. This
is usually the result of a cylinder head gasket leak or
crack in engine. Repair as necessary.
If there is not an immediate pressure increase,
pump the Pressure Tester. Do this until indicated
pressure is within system range of 110 kPa (16 psi).
Fluctuation of the gauge pointer indicates compres-
sion or combustion leakage into cooling system.
Because the vehicle is equipped with a catalytic
converter,do notshort out cylinders to isolate com-
pression leak.
If the needle on dial of the pressure tester does not
fluctuate, race engine a few times to check for an
abnormal amount of coolant or steam. This would be
emitting from exhaust pipe. Coolant or steam from
exhaust pipe may indicate a faulty cylinder head gas-
ket, cracked engine cylinder block or cylinder head.
A convenient check for exhaust gas leakage into
cooling system is provided by a commercially avail-
able Block Leak Check tool. Follow manufacturers
instructions when using this product.
COMBUSTION LEAKAGE TESTÐWITHOUT
PRESSURE TESTER
DO NOT WASTE reusable coolant. If the solution
is clean, drain the coolant into a clean container for
reuse.
Fig. 5 Leak Detection Using Black LightÐTypical
1 - TYPICAL BLACK LIGHT TOOL
7 - 6 COOLINGDR
COOLING (Continued)

CAUTION: Do not leave any one spark plug cable
disconnected for longer than necessary during test-
ing. This may cause possible heat damage to the
catalytic converter. Total test time must not exceed
ten minutes.
Except 5.7L V-8 :With the engine running,
remove spark plug cable from spark plug (one at a
time) and hold next to a good engine ground. If the
cable and spark plug are in good condition, the
engine rpm should drop and the engine will run
poorly. If engine rpm does not drop, the cable and/or
spark plug may not be operating properly and should
be replaced. Also check engine cylinder compression.
With the engine not running, connect one end of a
test probe to a good ground. Start the engine and run
the other end of the test probe along the entire
length of all spark plug cables. If cables are cracked
or punctured, there will be a noticeable spark jump
from the damaged area to the test probe. The cable
running from the ignition coil to the distributor cap
can be checked in the same manner. Cracked, dam-
aged or faulty cables should be replaced with resis-
tance type cable. This can be identified by the words
ELECTRONIC SUPPRESSION printed on the cable
jacket.Use an ohmmeter to test for open circuits, exces-
sive resistance or loose terminals. If equipped,
remove the distributor cap from the distributor.Do
not remove cables from cap.Remove cable from
spark plug. Connect ohmmeter to spark plug termi-
nal end of cable and to corresponding electrode in
distributor cap. Resistance should be 250 to 1000
Ohms per inch of cable. If not, remove cable from dis-
tributor cap tower and connect ohmmeter to the ter-
minal ends of cable. If resistance is not within
specifications as found in the SPARK PLUG CABLE
RESISTANCE chart, replace the cable. Test all spark
plug cables in this manner.
SPARK PLUG CABLE RESISTANCE
MINIMUM MAXIMUM
250 Ohms Per Inch 1000 Ohms Per Inch
3000 Ohms Per Foot 12,000 Ohms Per Foot
To test ignition coil-to-distributor cap cable (if
applicaple), do not remove the cable from the cap.
Connect ohmmeter to rotor button (center contact) of
distributor cap and terminal at ignition coil end of
cable. If resistance is not within specifications as
found in the Spark Plug Cable Resistance chart,
remove the cable from the distributor cap. Connect
the ohmmeter to the terminal ends of the cable. If
resistance is not within specifications as found in the
Spark Plug Cable Resistance chart, replace the cable.
Inspect the ignition coil tower for cracks, burns or
corrosion.
REMOVAL
5.9L V-8 / 8.0L V-10
CAUTION: When disconnecting a high voltage cable
from a spark plug or from the distributor cap, twist
the rubber boot slightly (1/2 turn) to break it loose
(Fig. 54). Grasp the boot (not the cable) and pull it
off with a steady, even force.
On 5.9L V-8 engines, spark plug cable heat shields
are pressed into the cylinder head to surround each
spark plug cable boot and spark plug (Fig. 53). These
shields protect the spark plug boots from damage
(due to intense engine heat generated by the exhaust
manifolds) and should not be removed. After the
spark plug cable has been installed, the lip of the
cable boot should have a small air gap to the top of
the heat shield (Fig. 53).
Fig. 53 HEAT SHIELDS - 5.9L V-8
1 - AIR GAP
2 - SPARK PLUG BOOT HEAT SHIELD
8I - 34 IGNITION CONTROLDR
SPARK PLUG CABLE (Continued)

EXHAUST SYSTEM
TABLE OF CONTENTS
page page
EXHAUST SYSTEM
DESCRIPTION
DESCRIPTION........................1
DESCRIPTION ± 5.9L DIESEL.............2
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - GAS ENGINE . . . 2
DIAGNOSIS AND TESTING - DIESEL
ENGINE..............................3
SPECIFICATIONS - TORQUE...............4
SPECIAL TOOLS........................4
CATALYTIC CONVERTER
DESCRIPTION - CATALYTIC CONVERTER.....4
OPERATION............................4
REMOVAL
REMOVAL............................5
REMOVAL............................5
INSPECTION...........................5
INSTALLATION
INSTALLATION........................5
INSTALLATION........................5
EXHAUST PIPE
REMOVAL
REMOVAL Ð 5.9L......................5
REMOVAL............................5
INSPECTION...........................6
INSTALLATION
INSTALLATION Ð 5.9L..................6
INSTALLATION........................7
EXHAUST PIPE
REMOVAL.............................7
INSPECTION...........................7
INSTALLATION..........................7
HEAT SHIELDS
DESCRIPTION..........................7
REMOVAL.............................7INSTALLATION..........................8
MUFFLER
REMOVAL.............................8
INSTALLATION..........................8
MUFFLER - 5.9L DIESEL
REMOVAL.............................9
INSTALLATION..........................9
TAILPIPE - 5.9L DIESEL
REMOVAL.............................9
INSPECTION...........................9
INSTALLATION..........................9
TAILPIPE
REMOVAL.............................10
INSPECTION..........................10
INSTALLATION.........................10
TURBOCHARGER SYSTEM
DIAGNOSIS AND TESTING -
TURBOCHARGER BOOST PRESSURE.....10
TURBOCHARGER
DESCRIPTION.........................11
OPERATION...........................11
REMOVAL.............................13
CLEANING............................14
INSPECTION..........................14
INSTALLATION.........................14
CHARGE AIR COOLER AND PLUMBING
DESCRIPTION.........................15
OPERATION...........................15
DIAGNOSIS AND TESTING - CHARGE AIR
COOLER SYSTEM - LEAKS..............15
REMOVAL.............................15
CLEANING............................16
INSPECTION..........................16
INSTALLATION.........................16
EXHAUST SYSTEM
DESCRIPTION
DESCRIPTION
CAUTION: Avoid application of rust prevention com-
pounds or undercoating materials to exhaust sys-
tem floor pan exhaust heat shields. Light overspray
near the edges is permitted. Application of coating
will result in excessive floor pan temperatures and
objectionable fumes.The federal gasoline engine exhaust system con-
sists of engine exhaust manifolds, exhaust pipes, cat-
alytic converter(s), extension pipe (if needed),
exhaust heat shields, muffler and exhaust tailpipe.
The California emission vehicles exhaust system
also contains the above components as well as mini
catalytic converters added to the exhaust pipe.
The exhaust system must be properly aligned to
prevent stress, leakage and body contact. Minimum
clearance between any exhaust component and the
body or frame is 25.4 mm (1.0 in.). If the system con-
tacts any body panel, it may amplify objectionable
noises from the engine or body.
DREXHAUST SYSTEM 11 - 1

DESCRIPTION ± 5.9L DIESEL
CAUTION: Avoid application of rust prevention com-
pounds or undercoating materials to exhaust sys-
tem floor pan exhaust heat shields. Light overspray
near the edges is permitted. Application of coating
will result in excessive floor pan temperatures and
objectionable fumes.
The diesel engine exhaust system consists of an
engine exhaust manifold, turbocharger, exhaust pipe,resonator, extension pipe (if needed), muffler and
exhaust tailpipe.
California emission vehicales include a catalytic
converter.
The exhaust system must be properly aligned to
prevent stress, leakage and body contact. The
exhaust components should be kept a minimum of
25.4 mm (1.0 in.) away from the body and frame. If
the system contacts any body panel, it may amplify
objectionable noises from the engine or body.
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - GAS ENGINE
EXHAUST SYSTEM DIAGNOSIS CHART
CONDITION POSSIBLE CAUSE CORRECTION
EXCESSIVE EXHAUST NOISE OR
LEAKING EXHAUST GASES1. Leaks at pipe joints. 1. Tighten clamps/bolts at leaking
joints.
2. Rusted or blown out muffler. 2. Replace muffler. Inspect exhaust
system.
3. Broken or rusted out exhaust
pipe.3. Replace exhaust pipe.
4. Exhaust pipe leaking at manifold
flange.4. Tighten/replace flange attaching
nuts/bolts.
5. Exhaust manifold cracked or
broken.5. Replace exhaust manifold.
6. Leak between exhaust manifold
and cylinder head.6. Tighten exhaust manifold to
cylinder head bolts.
7. Catalytic converter rusted or
blown out.7. Replace catalytic converter assy.
8. Restriction in exhaust system. 8. Remove restriction, if possible.
Replace restricted part if necessary.
CAUTION:
When servicing and replacing exhaust system components, disconnect the oxygen sensor connector(s). Allowing
the exhaust to hang by the oxygen sensor wires will damage the harness and/or sensor.
11 - 2 EXHAUST SYSTEMDR
EXHAUST SYSTEM (Continued)

SPECIFICATIONS - TORQUE
DESCRIPTION N´m Ft. In.
Lbs. Lbs.
Adjusting StrapÐBolt 23 Ð 200
Air Heater Power SupplyÐ
Nuts14 Ð 124
Air Inlet HousingÐBolts 24 18 Ð
Cab Heater Supply/Return
LineÐNuts24 18 Ð
Exhaust ClampÐNuts 48 35 Ð
Exhaust Manifold to Cylinder
HeadÐBolts
(Diesel Engine) 43 32 Ð
Exhaust Manifold to Cylinder
HeadÐBolts
(5.9L) 31 23 Ð
Exhaust Manifold to Cylinder
HeadÐBolts
(8.0L) 22 Ð 195
Exhaust Pipe to ManifoldÐ
Bolts31 23 Ð
Generator MountingÐBolts 41 30 Ð
Charge Air Cooler
MountingÐBolts2Ð17
Charge Air Cooler DuctÐ
Nuts11 Ð 9 5
Heat ShieldÐNuts and Bolts 11 Ð 95
Turbocharger flange studs 24 18 Ð
Turbocharger MountingÐ
Nuts43 32 Ð
Turbocharger Oil Drain
TubeÐBolts24 18 Ð
Turbocharger Oil Supply
LineÐFitting24 18 Ð
Turbocharger V-Band
ClampÐNut9Ð75
Turbocharger Oil Supply
fitting (at Turbocharger)36 27 Ð
Turbocharger Oil Supply
fitting (at lube filter head)24 18 Ð
Turbocharger Drain Hose
Clamps8Ð71
SPECIAL TOOLS
CATALYTIC CONVERTER
DESCRIPTION - CATALYTIC CONVERTER
WARNING: THE NORMAL OPERATING TEMPERA-
TURE OF THE EXHAUST SYSTEM IS VERY HIGH.
THEREFORE, NEVER WORK AROUND OR ATTEMPT
TO SERVICE ANY PART OF THE EXHAUST SYSTEM
UNTIL IT IS COOLED. SPECIAL CARE SHOULD BE
TAKEN WHEN WORKING NEAR THE CATALYTIC
CONVERTER. THE TEMPERATURE OF THE CON-
VERTER RISES TO A HIGH LEVEL AFTER A SHORT
PERIOD OF ENGINE OPERATION TIME.
CAUTION: DO NOT remove spark plug wires from
plugs or by any other means short out cylinders.
Failure of the catalytic converter can occur due to a
temperature increase caused by unburned fuel
passing through the converter.
The stainless steel catalytic converter body is
designed to last the life of the vehicle. Excessive heat
can result in bulging or other distortion, but exces-
sive heat will not be the fault of the converter. If
unburned fuel enters the converter, overheating may
occur. If a converter is heat-damaged, correct the
cause of the damage at the same time the converter
is replaced. Also, inspect all other components of the
exhaust system for heat damage.
Unleaded gasoline must be used to avoid con-
taminating the catalyst core.
50 State emission vehicles incorporate two mini
catalytic converters located after the exhaust mani-
folds and before the inline catalytic converter.
OPERATION
The catalytic converter captures and burns any
unburned fuel mixture exiting the combustion cham-
bers during the exhaust stroke of the engine. This
process aids in reducing emissions output.
TURBOCHARGER TESTER 9022
11 - 4 EXHAUST SYSTEMDR
EXHAUST SYSTEM (Continued)

REMOVAL
REMOVAL
WARNING: IF TORCHES ARE USED WHEN WORK-
ING ON THE EXHAUST SYSTEM, DO NOT ALLOW
THE FLAME NEAR THE FUEL LINES.
(1) Raise and support the vehicle.
(2) Saturate the bolts and nuts with heat valve
lubricant. Allow 5 minutes for penetration.
(3) Remove the bolts from the crossover pipe to the
catalytic converter connection.
(4) Disconnect oxygen sensor wiring.
(5) Loosen the nuts from the clamp that hold the
catalytic converter to the exhaust pipe flange connec-
tion.
NOTE: Do not remove nut from T-Bolt. Only remove
nut far enough, so that the T end can be removed
from the clamp.
(6) Remove the T bolt end of the fastener, from the
clamp.
(7) Spread the clamp, and remove the catalytic
converter from the vehicle.
(8) Discard the clamp.
NOTE: The catalytic converter to exhaust manifold
clamp is not reusable. Always use a new clamp
when reinstalling the catalytic converter.
REMOVAL
(1) Raise and support vehicle.
(2) Saturate the bolts and nuts with heat valve
lubricant. Allow 5 minutes for penetration.
(3) Remove clamps and nuts.
(4) Remove the catalytic converter.
INSPECTION
Look at the stainless steel body of the converter,
inspect for bulging or other distortion that could be a
result of overheating. If the converter has a heat
shield attached make sure it is not bent or loose.
If you suspect internal damage to the catalyst, tap-
ping the bottom of the catalyst with a rubber mallet
may indicate a damaged core.
INSTALLATION
INSTALLATION
NOTE: The catalytic converter to exhaust manifold
clamp is not reusable. Always use a new clamp
when reinstalling the catalytic converter.(1) Position the catalytic converter onto the
exhaust pipe flange connection. Tighten the nuts to
28 N´m (250 in. lbs.) torque.
(2) Install the muffler onto the catalytic converter
until the alignment tab is inserted into the align-
ment slot.
(3) Install the exhaust clamp at the muffler and
catalytic converter connection. Tighten the clamp
nuts to 47 N´m (35 ft. lbs.) torque.
(4) Connect oxygen sensor wiring.
(5) Lower the vehicle.
(6) Start the engine and inspect for exhaust leaks
and exhaust system contact with the body panels.
Adjust the alignment, if needed.
INSTALLATION
(1) Assemble converter and clamps loosely in
place.
(2) Install the exhaust pipe onto exhaust mani-
folds, tighten 31 N´m (23 ft. lbs.).
(3) Tighten all clamp nuts to 48 N´m (35 ft. lbs.)
torque.
(4) Lower the vehicle.
(5) Start the engine and inspect for exhaust leaks
and exhaust system contact with the body panels. A
minimum of 25.4 mm (1.0 in.) is required between
exhaust system components and body/frame parts.
Adjust the alignment, if needed.
EXHAUST PIPE
REMOVAL
REMOVAL Ð 5.9L
(1) Raise and support the vehicle.
(2) Saturate the bolts and nuts with heat valve
lubricant. Allow 5 minutes for penetration.
(3) Remove exhaust pipe to manifold bolts, retain-
ers and nuts.
(4) Remove the clamp nuts.
(5) Remove the exhaust pipe (Fig. 1).
REMOVAL
CAUTION: When servicing or replacing exhaust
system components, disconnect the oxygen sensor
connector(s). Allowing the exhaust to hang by the
oxygen sensor wires will damage the harness
and/or sensor.
(1) Raise and support the vehicle.
(2) Saturate the bolts and nuts with MopartRust
Penetrant. Allow 5 minutes for penetration.
(3) Disconnect the oxygen sensor(s).
DREXHAUST SYSTEM 11 - 5
CATALYTIC CONVERTER (Continued)

(4) Remove the exhaust manifold-to-exhaust pipe
nuts (Fig. 2).
(5) Remove exhaust pipe to converter exhaust
clamp.
(6) Disconnect the exhaust pipe from the catalytic
converter front flange.
(7) Remove the exhaust pipe.
INSPECTION
Discard rusted clamps, broken or worn supports
and attaching parts. Replace a component with orig-
inal equipment parts, or equivalent. This will assure
proper alignment with other parts in the system and
provide acceptable exhaust noise levels.
INSTALLATION
INSTALLATION Ð 5.9L
(1) Position the exhaust pipe for proper clearance
with the frame and underbody parts. A minimum
clearance of 25.4 mm (1.0 in.) is required.
(2) Position the exhaust pipe to manifold. Install
the bolts, retainers and nuts. Tighten the nuts to 31
N´m (23 ft. lbs.) torque.
(3) Tighten the clamp nuts to 48 N´m (35 ft. lbs.)
torque.
(4) Lower the vehicle.
(5) Start the engine and inspect for exhaust leaks
and exhaust system contact with the body panels.
Adjust the alignment, if needed (Fig. 1) and (Fig. 3).
Fig. 1 Exhaust Pipe to Manifold Connection ± 5.9L
1 - BOLT
2 - RETAINER
3 - EXHAUST MANIFOLD
4 - NUT
5 - EXHAUST PIPE
Fig. 2 Exhaust Pipe(s) to Manifold Connection
1 - BOLT
2 - RETAINER
3 - EXHAUST MANIFOLD
4 - NUT
5 - EXHAUST PIPE
Fig. 3 Exhaust Pipe-to-Catalytic Converter Flange
Alignment Ð Typical
1 - 7.874±17.526 mm (0.31±0.69 in.)
2 - CATALYTIC CONVERTER FLANGE
3 - 20 mm (0.79 in.) MIN.
4 - CROSSMEMBER
5 - EXHAUST PIPE
6 - EXHAUST PIPE
11 - 6 EXHAUST SYSTEMDR
EXHAUST PIPE (Continued)

INSTALLATION
(1) Connect the exhaust pipe(s) to the exhaust
manifold. Tighten the nuts to 34 N´m (25 ft. lbs.)
torque.
(2) Align and connect the exhaust pipe to the cat-
alytic converter flange (Fig. 4). Install exhaust clamp
and tighten clamp nuts to 47 N´m (35 ft. lbs.) torque.
(3) Connect oxygen sensor connector(s).
(4) Lower the vehicle.
(5) Start the engine and inspect for exhaust leaks
and exhaust system contact with the body panels.
Adjust the alignment, if needed.
EXHAUST PIPE
REMOVAL
(1) Disconnect the battery negative cables.
(2) Raise and support the vehicle on a hoist.
(3) Saturate the bolts and nuts with heat valve
lubricant. Allow 5 minutes for penetration.
(4) Remove the exhaust pipe-to-extension pipe
clamp. Separate the exhaust pipe and extension pipe.
(5) Remove the exhaust pipe-to-turbocharger elbow
clamp (Fig. 5).
(6) Remove the exhaust pipe from the transmis-
sion support (Fig. 5).
INSPECTION
Discard rusted clamps, broken or worn supports
and attaching parts. Replace a component with orig-
inal equipment parts, or equivalent. This will assure
proper alignment with other parts in the system and
provide acceptable exhaust noise levels.
INSTALLATION
(1) Install the exhaust pipe into the transmission
support and onto the turbocharger flange.
(2) Install the exhaust pipe-to-turbocharger elbow
clamp and tighten to 31 N´m (23 ft. lbs.) torque.
(3) Install the extension pipe and clamp to the
exhaust pipe using a new clamp and tighten the
clamp nuts to 48 N´m (35 ft. lbs.) torque.
(4) Lower the vehicle.
(5) Connect the battery negative cables.
(6) Start the engine and inspect for exhaust leaks
and exhaust system contact with the body panels. A
minimum of 25.4 mm (1.0 in.) is required. Adjust the
alignment, if needed.
HEAT SHIELDS
DESCRIPTION
There are two types of heat shields used. One is
stamped steel the other is molded foil sheets. The
shields attach to the vehicle around the exhaust sys-
tem to prevent heat from the exhaust system from
entering the passenger area and other areas where
the heat can cause damage to other components.
REMOVAL
(1) Raise and support the vehicle.
(2) Remove the nuts or bolts holding the exhaust
heat shield to the floor pan (Fig. 6) (Fig. 7) (Fig. 8),
crossmember or bracket.
Fig. 4 Exhaust Pipe-to-Catalytic Converter Flange
AlignmentÐTypical
1 - 7.874±17.526 mm (0.31±0.69 in.)
2 - CATALYTIC CONVERTER FLANGE
3 - 20 mm (0.79 in.) MIN.
4 - CROSSMEMBER
5 - EXHAUST PIPE
6 - EXHAUST PIPE
Fig. 5 Exhaust Pipe
1 - Clamp
2 - Support
3 - EXHAUST PIPE
DREXHAUST SYSTEM 11 - 7
EXHAUST PIPE (Continued)

Downstream Sensor - Federal Emissions
Package :The downstream oxygen sensor (1/2) is
also used to determine the correct air-fuel ratio. As
the oxygen content changes at the downstream sen-
sor, the PCM calculates how much air-fuel ratio
change is required. The PCM then looks at the
upstream oxygen sensor voltage and changes fuel
delivery until the upstream sensor voltage changes
enough to correct the downstream sensor voltage
(oxygen content).
The downstream oxygen sensor also provides an
input to determine catalytic convertor efficiency.
Upstream Sensors - California Emissions
Package :Two upstream sensors are used (1/1 and
2/1). The 1/1 sensor is the first sensor to receive
exhaust gases from the #1 cylinder. They provide an
input voltage to the PCM. The input tells the PCM
the oxygen content of the exhaust gas. The PCM uses
this information to fine tune fuel delivery to main-
tain the correct oxygen content at the downstream
oxygen sensors. The PCM will change the air/fuel
ratio until the upstream sensors input a voltage that
the PCM has determined will make the downstream
sensors output (oxygen content) correct.
The upstream oxygen sensors also provide an input
to determine mini-catalyst efficiency. Main catalytic
convertor efficiency is not calculated with this pack-
age.
Downstream Sensors - California Emissions
Package :Two downstream sensors are used (1/2
and 2/2). The downstream sensors are used to deter-
mine the correct air-fuel ratio. As the oxygen content
changes at the downstream sensor, the PCM calcu-
lates how much air-fuel ratio change is required. The
PCM then looks at the upstream oxygen sensor volt-
age, and changes fuel delivery until the upstream
sensor voltage changes enough to correct the down-
stream sensor voltage (oxygen content).
The downstream oxygen sensors also provide an
input to determine mini-catalyst efficiency. Main cat-
alytic convertor efficiency is not calculated with this
package.
Engines equipped with either a downstream sen-
sor(s), or a post-catalytic sensor, will monitor cata-
lytic convertor efficiency. If efficiency is below
emission standards, the Malfunction Indicator Lamp
(MIL) will be illuminated and a Diagnostic Trouble
Code (DTC) will be set. Refer to Monitored Systems
in Emission Control Systems for additional informa-
tion.
REMOVAL
CAUTION: Never apply any type of grease to the
oxygen sensor electrical connector, or attempt any
soldering of the sensor wiring harness.Refer to (Fig. 39) or (Fig. 40) for typical O2S (oxy-
gen sensor) locations.
WARNING: THE EXHAUST MANIFOLD, EXHAUST
PIPES AND CATALYTIC CONVERTER BECOME
VERY HOT DURING ENGINE OPERATION. ALLOW
ENGINE TO COOL BEFORE REMOVING OXYGEN
SENSOR.
(1) Raise and support vehicle.
(2) Disconnect wire connector from O2S sensor.
CAUTION: When disconnecting sensor electrical
connector, do not pull directly on wire going into
sensor.
(3) Remove O2S sensor with an oxygen sensor
removal and installation tool.
(4) Clean threads in exhaust pipe using appropri-
ate tap.
Fig. 39 O2 SENSOR SYSTEM - WITH 4 SENSORS
Fig. 40 O2 SENSOR SYSTEM - WITH 2 SENSORS
1 - POST CATALYST OXYGEN SENSOR (1/3)
2 - PRE-CATALYST OXYGEN SENSOR (1/2)
14 - 44 FUEL INJECTION - GASDR
OXYGEN SENSOR (Continued)

pump by drawing air into the pump cavity and also
closes the vent seal. During non test conditions the
vent seal is held open by the pump diaphragm
assembly which pushes it open at the full travel posi-
tion. The vent seal will remain closed while the
pump is cycling due to the reed switch triggering of
the three port solenoid that prevents the diaphragm
assembly from reaching full travel. After the brief
initialization period, the solenoid is de-energized
allowing atmospheric pressure to enter the pump
cavity, thus permitting the spring to drive the dia-
phragm which forces air out of the pump cavity and
into the vent system. When the solenoid is energized
and de energized, the cycle is repeated creating flow
in typical diaphragm pump fashion. The pump is con-
trolled in 2 modes:
Pump Mode: The pump is cycled at a fixed rate to
achieve a rapid pressure build in order to shorten the
overall test length.
Test Mode: The solenoid is energized with a fixed
duration pulse. Subsequent fixed pulses occur when
the diaphragm reaches the Switch closure point.
The spring in the pump is set so that the system
will achieve an equalized pressure of about 7.5º H20.
The cycle rate of pump strokes is quite rapid as the
system begins to pump up to this pressure. As the
pressure increases, the cycle rate starts to drop off. If
there is no leak in the system, the pump would even-
tually stop pumping at the equalized pressure. If
there is a leak, it will continue to pump at a rate rep-
resentative of the flow characteristic of the size of the
leak. From this information we can determine if the
leak is larger than the required detection limit (cur-
rently set at .040º orifice by CARB). If a leak is
revealed during the leak test portion of the test, the
test is terminated at the end of the test mode and no
further system checks will be performed.
After passing the leak detection phase of the test,
system pressure is maintained by turning on the
LDP's solenoid until the purge system is activated.
Purge activation in effect creates a leak. The cycle
rate is again interrogated and when it increases due
to the flow through the purge system, the leak check
portion of the diagnostic is complete.
The canister vent valve will unseal the system
after completion of the test sequence as the pump
diaphragm assembly moves to the full travel position.
Evaporative system functionality will be verified by
using the stricter evap purge flow monitor. At an
appropriate warm idle the LDP will be energized to
seal the canister vent. The purge flow will be clocked
up from some small value in an attempt to see a
shift in the 02 control system. If fuel vapor, indicated
by a shift in the 02 control, is present the test is
passed. If not, it is assumed that the purge system isnot functioning in some respect. The LDP is again
turned off and the test is ended.
MISFIRE MONITOR
Excessive engine misfire results in increased cata-
lyst temperature and causes an increase in HC emis-
sions. Severe misfires could cause catalyst damage.
To prevent catalytic convertor damage, the PCM
monitors engine misfire.
The Powertrain Control Module (PCM) monitors
for misfire during most engine operating conditions
(positive torque) by looking at changes in the crank-
shaft speed. If a misfire occurs the speed of the
crankshaft will vary more than normal.
FUEL SYSTEM MONITOR
To comply with clean air regulations, vehicles are
equipped with catalytic converters. These converters
reduce the emission of hydrocarbons, oxides of nitro-
gen and carbon monoxide. The catalyst works best
when the Air Fuel (A/F) ratio is at or near the opti-
mum of 14.7 to 1.
The PCM is programmed to maintain the optimum
air/fuel ratio of 14.7 to 1. This is done by making
short term corrections in the fuel injector pulse width
based on the O2S sensor output. The programmed
memory acts as a self calibration tool that the engine
controller uses to compensate for variations in engine
specifications, sensor tolerances and engine fatigue
over the life span of the engine. By monitoring the
actual fuel-air ratio with the O2S sensor (short term)
and multiplying that with the program long-term
(adaptive) memory and comparing that to the limit,
it can be determined whether it will pass an emis-
sions test. If a malfunction occurs such that the PCM
cannot maintain the optimum A/F ratio, then the
MIL will be illuminated.
CATALYST MONITOR
To comply with clean air regulations, vehicles are
equipped with catalytic converters. These converters
reduce the emission of hydrocarbons, oxides of nitro-
gen and carbon monoxide.
Normal vehicle miles or engine misfire can cause a
catalyst to decay. This can increase vehicle emissions
and deteriorate engine performance, driveability and
fuel economy.
The catalyst monitor uses dual oxygen sensors
(O2S's) to monitor the efficiency of the converter. The
dual O2S's sensor strategy is based on the fact that
as a catalyst deteriorates, its oxygen storage capacity
and its efficiency are both reduced. By monitoring
the oxygen storage capacity of a catalyst, its effi-
ciency can be indirectly calculated. The upstream
O2S is used to detect the amount of oxygen in the
exhaust gas before the gas enters the catalytic con-
DREMISSIONS CONTROL 25 - 3
EMISSIONS CONTROL (Continued)