1999 DODGE NEON check engine light

33.34 mm (1-5/16 inches). Turn tool table until sur-
face is in line with the 33.34 mm (1-5/16 inch) mark
on the threaded stud and the zero mark on the front.
Place spring over stud on the table and lift compress-
ing lever to set tone device (Fig. 105). Pull on torque
wrench until ping is heard. Take reading on torque
wrench at this instant. Multiply this reading by two.
This will give the spring load at test length. Frac-
tional measurements are indicated on the table for
finer adjustments. Discard the springs that do not
meet specifications. The Following specifications
apply to both intake and exhaust valve springs.
²Valve Closed Nominal ForceÐ 67 lbs. @ 39.8 mm
(1.57 in.)
²Valve Open Nominal ForceÐ 160 lbs. @ 32.6 mm
(1.28 in.)
(2) Verify springs are not distorted with a steel
square and surface plate, check springs from both
ends. If the spring is more than 1.5 mm (1/16 inch)
out of square, install a new spring.
REFACING VALVES AND VALVE SEATS
(1) The intake and exhaust valve seats and valve
face have a 45 degree angle.(2) Inspect the remaining margin after the valves
are refaced (Fig. 106). Intake valves with less than
0.95 mm (1/32 inch.) margin and Exhaust valves
with less than 1.05 mm (3/64 inch) margin should be
discarded.
(3) When refacing valve seats, it is important that
the correct size valve guide pilot be used for reseat-
ing stones. A true and complete surface must be
obtained. For valve specifications see Valve Specifica-
tion Chart.
(4) Measure the concentricity of valve seat and
valve guide using a valve seat runout dial indicator.
Total runout should not exceed. 0.051 mm (0.002
inch.) (total indicator reading).
(5) Inspect the valve seat with Prussian blue to
determine where the valve contacts the seat. To do
this, coat valve seatLIGHTLYwith Prussian blue
then set valve in place. Rotate the valve with light
pressure. If the blue is transferred to the center of
valve face, contact is satisfactory. If the blue is trans-
ferred to top edge of the valve face, lower valve seat
with a 15 degrees stone. If the blue is transferred to
the bottom edge of valve face raise valve seat with a
65 degrees stone.
²Intake valve seat diameter is 33 mm (1.299 in.)
VALVE GUIDE SPECIFICATION CHART
Valve Guide Diameter
Intake Valve Exhaust Valve
5.975 - 6.000
mm (0.2352 -
0.2362 in.)5.975 - 6.000
mm (0.2352 -
0.2362 in.)
Valve Guide Clearance
Intake Valve Exhaust Valve
New: 0.023 - 0.066
mm (0.001 -
0.0025 in.)0.051 - 0.094
mm (0.002 -
0.0037 in.)
Service Limit: 0.25 mm (0.010 in.)
Fig. 104 Valve Guide Height
Fig. 105 Valve Spring Testing
Fig. 106 Intake and Exhaust Valve Refacing
9 - 48 2.0L SOHC ENGINEPL
DISASSEMBLY AND ASSEMBLY (Continued)

CAUTION: When depressing the valve spring
retainers with valve spring compressor the locks
can become dislocated. Check to make sure both
locks are in their correct location after removing
tool.
(4) Check the valve spring installed height B after
refacing the valve and seat (Fig. 108). Make sure
measurements are taken from top of spring seat to
the bottom surface of spring retainer. If height is
greater than 40.18 mm (1.58 in.), install a 0.762 mm
(0.030 in.) spacer under the valve spring seat to
bring spring height back within specification.
(5) Install rocker arm shafts as previously
described in this section.
(6) Checking dry lash. Dry lash is the amount of
clearance that exists between the base circle of an
installed cam and the rocker arm roller when the
adjuster is drained of oil and completely collapsed.
Specified dry lash is 1.17 mm (0.046 in.) for intake
and 1.28 mm (0.050 in.) for exhaust. After performing
dry lash check, refill adjuster with oil and allow 10
minutes for adjuster/s to bleed down before rotating
cam.
CLEANING AND INSPECTION
CYLINDER HEAD AND CAMSHAFT JOURNALS
INSPECTING CYLINDER HEAD
Cylinder head must be flat within 0.1 mm (0.004
inch) (Fig. 110).
Inspect cylinder head camshaft bearings for wear.
Check camshaft journals for scratches and worn
areas. If light scratches are present, they may be
removed with 400 grit sand paper. If deep scratches
are present, replace the camshaft and check the cyl-
inder head for damage. Replace the cylinder head ifworn or damaged. Check the lobes for pitting and
wear. If the lobes show signs of wear, check the cor-
responding rocker arm roller for wear or damage.
Replace rocker arm/hydraulic lash adjuster if worn or
damaged. If lobes show signs of pitting on the nose,
flank or base circle; replace the camshaft.
CLEANING
Remove all gasket material from cylinder head and
block. Be careful not to gouge or scratch the alumi-
num head sealing surface.
OIL PUMP
(1) Clean all parts thoroughly. Mating surface of
the oil pump should be smooth. Replace pump cover
if scratched or grooved.
(2) Lay a straightedge across the pump cover sur-
face (Fig. 111). If a 0.076 mm (0.003 inch.) feeler
gauge can be inserted between cover and straight
edge, cover should be replaced.
(3) Measure thickness and diameter of outer rotor.
If outer rotor thickness measures 7.64 mm (0.301
inch.) or less (Fig. 112), or if the diameter is 79.95
mm (3.148 inches) or less, replace outer rotor.
(4) If inner rotor measures 7.64 mm (.301 inch) or
less replace inner rotor (Fig. 113).
(5) Slide outer rotor into pump housing, press to
one side with fingers and measure clearance between
rotor and housing (Fig. 114). If measurement is 0.39
mm (0.015 inch.) or more, replace housing only if
outer rotor is in specification.
(6) Install inner rotor into pump housing. If clear-
ance between inner and outer rotors (Fig. 115) is .203
mm (.008 inch) or more, replace both rotors.
(7) Place a straightedge across the face of the
pump housing, between bolt holes. If a feeler gauge
of .102 mm (.004 inch) or more can be inserted
between rotors and the straightedge, replace pump
assembly (Fig. 116).ONLYif rotors are in specs.
Fig. 110 Checking Cylinder Head Flatness
Fig. 111 Checking Oil Pump Cover Flatness
9 - 50 2.0L SOHC ENGINEPL
DISASSEMBLY AND ASSEMBLY (Continued)

Chart for specifications. Replace guides if they are
not within specification.
CHECK VALVE GUIDE HEIGHT
TESTING VALVE SPRINGS
(1) Whenever valves have been removed for inspec-
tion, reconditioning or replacement, valve springs
should be tested Special Tool C-647. As an example,
the compression length of the spring to be tested is
33.34 mm (1-5/16 inches). Turn tool table until sur-
face is in line with the 33.34 mm (1-5/16 inch) mark
on the threaded stud and the zero mark on the front.
Place spring over stud on the table and lift compress-
ing lever to set tone device (Fig. 97). Pull on torque
wrench until ping is heard. Take reading on torque
wrench at this instant. Multiply this reading by two.This will give the spring load at test length. Frac-
tional measurements are indicated on the table for
finer adjustments. Discard the springs that do not
meet specifications. The Following specifications
apply to both intake and exhaust valve springs:
²Valve Closed Compression Pressure: 246 ± 270 N
@ 38.0 mm (55 ± 60 lbs. @ 1.50 in.)
²Valve Open Compression Pressure: 549 ± 611 N
@ 29.25 mm (123 ± 137 lbs. @ 1.17 in.)
(2) Verify springs are not distorted with a steel
square and surface plate. Check springs from both
ends. Replace spring if the spring is more than 1.5
mm (1/16 inch) out of square.
REFACING VALVES AND VALVE SEATS
(1) The intake and exhaust valve seats and valve
face have a 45 and a 45 1/2 degree angles.
(2) Inspect the remaining margin after the valves
are refaced (Fig. 98). Intake valves with less than 1.2
mm (3/64 inch.) margin and Exhaust valves with less
than 0.9 mm (1/32 inch.) margin should be discarded.
(3) When refacing valve seats, it is important that
the correct size valve guide pilot be used for the
reseating stones. A true and complete surface must
be obtained.
(4) Measure the concentricity of valve seat and
valve guide using a valve seat runout dial indicator.
Total runout should not exceed. 0.051 mm (0.002
inch.) (total indicator reading).
(5) Inspect the valve seat with Prussian blue to
determine where the valve contacts the seat. To do
this, coat valve seatLIGHTLYwith Prussian blue
then set valve in place. Rotate the valve with light
pressure. If the blue is transferred to the center of
valve face, contact is satisfactory. If the blue is trans-
ferred to top edge of the valve face, lower valve seat
with a 15 degrees stone. If the blue is transferred to
the bottom edge of valve face raise valve seat with a
65 degrees stone.
Fig. 96 Checking Wear on Valve GuideÐTypical
VALVE GUIDE SPECIFICATION CHART
Valve Guide
DiameterIntake Valve Exhaust Valve
5.975 - 6.000 mm
(0.2352 - 0.2362
in.)5.975 - 6.000 mm
(0.2352 - 0.2362
in.)
Valve Guide
ClearanceIntake Valve Exhaust Valve
New: 0.023 - 0.066 mm
(0.001 - 0.0025
in.)0.051 - 0.094 mm
(0.002 - 0.0037
in.)
Service Limit: 0.25 mm (0.010 in.)
Valve Guide Height
Fig. 97 Testing Valve Spring
9 - 92 2.0L DOHC ENGINEPL
DISASSEMBLY AND ASSEMBLY (Continued)

CAUTION: If oversize valves are used, there is only
one oversize valve available. The same stem seal is
used on both the standard and oversize valve.
(3) Install valve springs and retainers. Compress
valve springs only enough to install locks, taking
care not to misalign the direction of compression.
Nicked valve stems may result from misalignment of
the valve spring compressor.
CAUTION: When depressing the valve spring
retainers with valve spring compressor the locks
can become dislocated. Check to make sure both
locks are in their correct location after removing
tool.
(4) Check the valve spring installed height B after
refacing the valve and seat (Fig. 100). Make sure
measurements are taken from top of spring seat to
the bottom surface of spring retainer. If height is
greater than 38.75 mm (1.525 in.), install a 7.620
mm (0.030 inch.) spacer under the valve spring seat
to bring spring height back within specification.
(5) Install cam followers and camshaft as previ-
ously described in this section.
(6) Checking dry lash. Dry lash is the amount of
clearance that exists between the base circle of an
installed cam and the rocker arm roller when the
adjuster is drained of oil and completely collapsed.
Specified dry lash is 1.17 mm (0.046 in.) for intake
and 1.28 mm (0.050 in.) for exhaust. After performing
dry lash check, refill adjuster with oil and allow 10
minutes for adjuster or adjusters to bleed down
before rotating cam.
CLEANING AND INSPECTION
CYLINDER HEAD AND CAMSHAFT JOURNALS
INSPECTING CYLINDER HEAD
Cylinder head must be flat within 0.1 mm (0.004
inch) (Fig. 102).Inspect cylinder head camshaft bearings for wear.
Check camshaft journals for scratches and worn
areas. If light scratches are present, they may be
removed with 400 grit sand paper. If deep scratches
are present, replace the camshaft and check the cyl-
inder head for damage. Replace the cylinder head if
worn or damaged. Check the lobes for pitting and
wear. If the lobes show signs of wear, check the cor-
responding rocker arm roller for wear or damage.
Replace rocker arm/hydraulic lash adjuster if worn or
damaged. If lobes show signs of pitting on the nose,
flank or base circle; replace the camshaft.
CLEANING
Remove all gasket material from cylinder head and
block. Be careful not to gouge or scratch the alumi-
num head sealing surface.
OIL PUMP
(1) Clean all parts thoroughly. Mating surface of
the oil pump should be smooth. Replace pump cover
if scratched or grooved.
(2) Lay a straightedge across the pump cover sur-
face (Fig. 103). If a 0.076 mm (0.003 inch.) feeler
gauge can be inserted between cover and straight
edge, cover should be replaced.
(3) Measure thickness and diameter of outer rotor.
If outer rotor thickness measures 7.64 mm (0.301
inch.) or less (Fig. 104), or if the diameter is 79.95
mm (3.148 inches) or less, replace outer rotor.
(4) If inner rotor measures 7.64 mm (.301 inch) or
less replace inner rotor (Fig. 105).
(5) Slide outer rotor into pump housing, press to
one side with fingers and measure clearance between
rotor and housing (Fig. 106). If measurement is 0.39
mm (0.015 inch.) or more, replace housing only if
outer rotor is in specification.
Fig. 101 Valve Stem Oil Seal ToolFig. 102 Checking Cylinder Head Flatness
9 - 94 2.0L DOHC ENGINEPL
DISASSEMBLY AND ASSEMBLY (Continued)

INSTALLATION
Before installing manifold. Clean all mating sur-
faces. Replace all seals, with new seals. All intakemanifold fasteners and washers are to be discarded
andNEWfasteners and washers are to be used.
(1) Install intake manifold onto cylinder head and
tighten fasteners to 12 N´m (105 in. lbs.) in sequence
shown in (Fig. 20).
(2) Install intake manifold to water inlet support.
Tighten fastener (Fig. 20) to 12 N´m (105 in. lbs.).
(3) Remove covering from fuel injector holes and
insure the holes are clean. Install fuel rail assembly
to intake manifold. Tighten screws to 23 N´m (200 in.
lbs.).
(4) Connect PCV and brake booster hoses.
(5) Inspect quick connect fittings for damage,
replace if necessary Refer to Group 14, Fuel System
for procedure. Apply a light amount of clean engine
oil to fuel inlet tube. Connect fuel supply hose to fuel
rail assembly. Check connection by pulling on connec-
tor to insure it locked into position.
(6) Install throttle body. Tighten fastener to 22
N´m (200 in. lbs.). Install transmission to throttle
body support bracket and tighten to 11.9 N´m (105
in. lbs.) at the throttle body first. Next tighten the
bracket at the transmission.
(7) Connect Manifold Absolute Pressure/Intake Air
Temperature Sensor (TMAP) wiring connector.
(8) Connect knock sensor connector, and wiring at
starter. Connect wiring harness to intake manifold
tab.
(9) Connect Idle Air Control (IAC) motor and
Throttle Position Sensor (TPS) wiring connectors.
(10) Connect vacuum hoses to throttle body.
(11) Install accelerator, kickdown and speed con-
trol cables to their bracket and connect them to the
throttle lever. Refer to Group 14, Fuel System Throt-
tle Body Installation for procedure.
(12) Loose assemble the EGR tube onto valve and
intake manifold finger tight. Tighten tube fasteners
at the EGR valve first to 11 N´m (95 in. lbs.) then,
tighten the intake manifold side fasteners to 11 N´m
(95 in. lbs.).
(13) Install clean air duct to air filter housing.
Tighten clamp to 3 N´m (30 in. lbs.).
(14) Connect negative cable to battery.
(15) Install fresh air duct to air cleaner and
tighten wing nut.
(16) With the DRB scan tool use ASD Fuel System
Test to pressurize system to check for leaks.
CAUTION: When using the ASD Fuel System Test,
the Auto Shutdown (ASD) relay will remain ener-
gized for 7 minutes or until the ignition switch is
turned to the OFF position, or Stop All Test is
selected.
Fig. 18 Knock Sensor
Fig. 19 EGR Tube Assembly
Fig. 20 Intake Manifold Tightening Sequence
11 - 8 EXHAUST SYSTEM AND INTAKE MANIFOLDPL
REMOVAL AND INSTALLATION (Continued)

INSTALLATION
Before installing manifolds. Clean all mating sur-
faces. Replace all gaskets, with new.
(1) Assemble lower manifold to upper (if sepa-
rated) and tighten bolts in sequence shown in (Fig.
29) to 28 N´m (250 in. lbs.).
(2) Install intake manifold onto cylinder head and
tighten fasteners to 28 N´m (250 in. lbs.) in sequence
shown in (Fig. 30).
(3) Remove covering from fuel injector holes and
insure the holes are clean. Install fuel rail assembly
to intake manifold. Tighten screws to 23 N´m (200 in.
lbs.).
(4) Connect PCV and brake booster hoses.
(5) Inspect quick connect fittings for damage,
replace if necessary Refer to Group 14, Fuel System
for procedure. Apply a light amount of clean engine
oil to fuel inlet tube. Connect fuel supply hose to fuel
rail assembly. Check connection by pulling on connec-
tor to insure it locked into position.
(6) Connect heater tube and hose to intake mani-
fold.
(7) Connect upper radiator hose and coolant recov-
ery hose.
(8) Connect coolant temperature sensor wiring con-
nector.
(9) Install throttle body. Tighten fastener to 22
N´m (200 in. lbs.).
(10) Connect Manifold Absolute Pressure/Intake
Air Temperature Sensor (TMAP) wiring connector.(11) Connect knock sensor connector and starter
wires. Connect wiring harness to heater tube tab.
(12) Connect Idle Air Control (IAC) motor and
Throttle Position Sensor (TPS) wiring connectors.
(13) Connect vacuum hoses to throttle body.
(14) Install accelerator, kickdown and speed con-
trol cables to their bracket and connect them to the
throttle lever. Refer to Group 14, Fuel System Throt-
tle Body Installation for procedure.
(15) Loose assemble the EGR tube onto valve and
intake manifold finger tight. Tighten tube fasteners
at the EGR valve first to 11 N´m (95 in. lbs.) then,
tighten the intake manifold side fasteners to 11 N´m
(95 in. lbs.).
(16) Install fresh air duct to air filter housing.
Tighten clamp to 3 N´m (25 in. lbs.).
(17) Connect negative cable to battery.
(18) With the DRB scan tool use ASD Fuel System
Test to pressurize system to check for leaks.
CAUTION: When using the ASD Fuel System Test,
the Auto Shutdown (ASD) relay will remain ener-
gized for 7 minutes or until the ignition switch is
turned to the OFF position, or Stop All Test is
selected.
EXHAUST MANIFOLD
REMOVAL
(1) Remove air cleaner assembly and bracket.
(2) Remove exhaust manifold heat shield (Fig. 31).
(3) Disconnect upstream heated oxygen sensor con-
nector.
Fig. 29 Lower Intake Manifold to Upper Tightening
Sequence
Fig. 30 Intake Manifold To Cylinder Head Tightening
Sequence
Fig. 31 Exhaust Manifold Heat Shield
PLEXHAUST SYSTEM AND INTAKE MANIFOLD 11 - 11
REMOVAL AND INSTALLATION (Continued)

WARNING: THE FUEL RESERVOIR OF THE FUEL
PUMP MODULE DOES NOT EMPTY OUT WHEN THE
TANK IS DRAINED. THE FUEL IN THE RESERVOIR
WILL SPILL OUT WHEN THE MODULE IS
REMOVED.
(2) Disconnect fuel line from fuel pump module by
depressing quick connect retainers with thumb and
fore finger.
(3) Slide fuel pump module electrical connecter
lock to unlock.
(4) Disconnect the electrical connection from the
fuel pump module, by pushing down on connector
retainer and pulling connector off of module.
(5) Use a transmission jack to support the fuel
tank. remove bolts from fuel tank straps.
(6) Lower tank slightly.
(7) Use Special Tool 6856 to remove fuel pump
module locknut (Fig. 17).
(8) Remove fuel pump and O-ring seal from tank.
Discard old seal.
INSTALLATION
(1) Wipe seal area of tank clean and place a new
seal in position in the tank opening.
(2) Position fuel pump in the tank. Make sure the
aligment tab on the underside of the fuel pump mod-
ule flange sits in the notch on the fuel tank.
(3)
Position the locknut over the fuel pump module.
(4) Tighten the locknut using Special Tool 6856 to
55 N´m (40.5 ft. lbs.) (Fig. 17).
CAUTION: Over tightening the pump lock ring may
result in a leak.
(5) Fill fuel tank. Check for leaks.
FUEL FILTER / PRESSURE REGULATOR
REMOVAL
WARNING: THE FUEL SYSTEM IS UNDER A CON-
STANT PRESSURE, EVEN WITH ENGINE OFF. BEFORE
SERVICING THE FUEL FILTER/FUEL PRESSURE REG-
ULATOR, THE FUEL SYSTEM PRESSURE MUST BE
RELEASED.
(1) Refer to Fuel System Pressure Release in the
Fuel Delivery System section of this group.
The fuel filter/fuel pressure regulator is located on
the top of fuel pump module. Fuel pump module
removal is not necessary.
(2) Raise vehicle on hoist.
(3) Disconnect fuel supply line at the Filter/Regu-
lator nipple (refer to Quick Connect Fittings in this
section).
(4) Depress locking spring tab on side of Fuel/Reg-
ulator (Fig. 18) and rotate 90É counter-clockwise and
pull out.
NOTE: Make sure that the upper and lower O-rings
are on the Filter/Regulator assembly.
INSTALLATION
Lightly lubricate the O-rings with engine oil.
(1) Insert Filter/Regulator into the opening in the
fuel pump module, align the two hold down tabs with
the flange.
(2) While applying downward pressure, rotate the
Filter/Regulator clockwise until the the spring tab
engages the locating slot (Fig. 19).
(3) Connect the fuel line to the Filter/Regulator.
(4) Lower vehicle from hoist.
Fig. 16 Fuel Pump Module Removal
Fig. 17 Fuel Tank Locknut
14 - 12 FUEL SYSTEMPL
REMOVAL AND INSTALLATION (Continued)

ENGINE START-UP MODE
This is an OPEN LOOP mode. If the vehicle is in
park or neutral (automatic transaxles) or the clutch
pedal is depressed (manual transaxles) the ignition
switch energizes the starter relay. The following
actions occur when the starter motor is engaged.
²If the PCM receives the camshaft position sensor
and crankshaft position sensor signals, it energizes
the Auto Shutdown (ASD) and fuel pump relays. If
the PCM does not receive both signals within approx-
imately one second, it will not energize the ASD
relay and fuel pump relay. The ASD and fuel pump
relays supply battery voltage to the fuel pump, fuel
injectors, ignition coil and heated oxygen sensors.
²The PCM energizes all four injectors (on the 69É
degree falling edge) for a calculated pulse width until
it determines crankshaft position from the camshaft
position sensor and crankshaft position sensor sig-
nals. The PCM determines crankshaft position within
1 engine revolution.
²After determining crankshaft position, the PCM
begins energizing the injectors in sequence. It adjusts
injector pulse width and controls injector synchroni-
zation by turning the individual ground paths to the
injectors On and Off.
²When the engine idles within664 RPM of its
target RPM, the PCM compares current MAP sensor
value with the atmospheric pressure value received
during the Ignition Switch On (zero RPM) mode. If
the PCM does not detect a minimum difference
between the two values, it sets a MAP diagnostic
trouble code into memory.
Once the ASD and fuel pump relays have been
energized, the PCM determines injector pulse width
based on the following:
²Battery voltage
²Engine coolant temperature
²Engine RPM
²Intake air temperature (IAT)
²Throttle position
²The number of engine revolutions since cranking
was initiated
During Start-up the PCM maintains ignition tim-
ing at 9É BTDC.
ENGINE WARM-UP MODE
This is an OPEN LOOP mode. The following inputs
are received by the PCM:
²Engine coolant temperature
²Manifold Absolute Pressure (MAP)
²Intake air temperature (IAT)
²Crankshaft position (engine speed)
²Camshaft position
²Knock sensor
²Throttle position
²A/C switch
²Battery voltage²Power steering pressure switch
²Vehicle speed
²Speed control
²Both O2 sensors
²All diagnostics
The PCM adjusts injector pulse width and controls
injector synchronization by turning the individual
ground paths to the injectors On and Off.
The PCM adjusts ignition timing and engine idle
speed. Engine idle speed is adjusted through the idle
air control motor.
CRUISE OR IDLE MODE
When the engine is at operating temperature this
is a CLOSED LOOP mode. During cruising or idle
the following inputs are received by the PCM:
²Intake air temperature
²Engine coolant temperature
²Manifold absolute pressure
²Crankshaft position (engine speed)
²Camshaft position
²Knock sensor
²Throttle position
²Exhaust gas oxygen content
²A/C control positions
²Power steering pressure switch
²Battery voltage
²Vehicle speed
The PCM adjusts injector pulse width and controls
injector synchronization by turning the individual
ground paths to the injectors On and Off.
The PCM adjusts engine idle speed and ignition
timing. The PCM adjusts the air/fuel ratio according
to the oxygen content in the exhaust gas (measured
by the upstream and downstream heated oxygen sen-
sor).
The PCM monitors for engine misfire. During
active misfire and depending on the severity, the
PCM either continuously illuminates or flashes the
malfunction indicator lamp (Check Engine light on
instrument panel). Also, the PCM stores an engine
misfire DTC in memory.
The PCM performs several diagnostic routines.
They include:
²Oxygen sensor monitor
²Downstream heated oxygen sensor diagnostics
during open loop operation (except for shorted)
²Fuel system monitor
²EGR monitor
²Purge system monitor
²All inputs monitored for proper voltage range.
²All monitored components (refer to Group 25 for
On-Board Diagnostics).
The PCM compares the upstream and downstream
heated oxygen sensor inputs to measure catalytic
convertor efficiency. If the catalyst efficiency drops
14 - 22 FUEL SYSTEMPL
GENERAL INFORMATION (Continued)