engine oil DODGE NEON 2000 Service Repair Manual

(8) Disconnect kick-down cable and remove from
bracket. Secure cable out of the way (Fig. 48).
(9) Raise vehicle on hoist.
(10) Remove transaxle oil pan and drain ATF into
a suitable container.
(11) Remove both axle shafts. Refer to Group 3,
Differential and Driveline for the correct procedures.(12) Remove the right engine-to-transaxle lateral
bending brace (Fig. 49).
(13) Disconnect the vehicle speed sensor connector
(Fig. 50).
Fig. 47 Gear Shift Cable at Transaxle
1 ± SHIFT LEVER
2 ± SHIFT CABLE
Fig. 48 Kickdown Cable at Transaxle
1 ± LEVER
2 ± BRACKET
3 ± KICKDOWN CABLE
Fig. 49 Right Lateral Bending Brace Removal/
Installation
1 ± TRANSAXLE
2 ± ENGINE
3 ± LATERAL BENDING BRACE
Fig. 50 Vehicle Speed Sensor Connector
1 ± CONNECTOR
2 ± SPEEDO PINION
3 ± O-RING
4 ± SENSOR
PLTRANSAXLE 21 - 85
REMOVAL AND INSTALLATION (Continued)

(14) Remove structural collar (Fig. 51).
(15) Remove the left engine-to-transaxle lateral
bending brace (Fig. 51).
(16) Remove bellhousing dust cover (Fig. 51).
(17) Remove starter motor (Fig. 52).
(18) Remove drive plate to converter bolts (Fig.
54).
(19) Support engine at oil pan with screw jack and
wood block.
(20) Remove transaxle upper mount thru-bolt.
Gain access to this bolt through the driver's side
wheel house (Fig. 53).
(21) Carefully lower engine and transaxle on screw
jack until proper removal clearance is obtained.
(22) Obtain a helper to assist in holding transaxle
while removing transaxle-to-engine mounting bolts
(Fig. 54).
(23) Remove transaxle from vehicle (Fig. 54).
(24) Remove torque converter from front pump.
(25) If installing a new or replacement transaxle,
remove the upper mount and bracket as shown in
(Fig. 55), and transfer to the replacement unit and
torque all bolts to 68 N´m (50 ft. lbs.) torque.
Fig. 51 Left Lateral Bending Brace and Structural
Collar
1 ± LATERAL BENDING BRACE
2 ± STRUCTURAL COLLAR
3 ± DUST COVER
Fig. 52 Starter Motor Removal/Installation
1 ± BOLT
2 ± GROUND
3±STARTER
4 ± BOLT
Fig. 53 Transaxle Upper Mount and Bracket
1 ± MOUNT BRACKET
2 ± BOLT
3 ± MOUNT
21 - 86 TRANSAXLEPL
REMOVAL AND INSTALLATION (Continued)

INSTALLATION
(1) Install torque converter into front pump.
Rotate converter until the hub fully engages front
pump gear lugs.
(2) Install transaxle-to-engine mounting bolts (Fig.
54) and tighten to 95 N´m (70 ft. lbs.) torque.
(3) Raise engine and transaxle with screw jack
until through hole in upper mount aligns with hole
in mount bracket. Install mount bolt and tighten to
108 N´m (80 ft. lbs.) torque (Fig. 53).
(4) Remove screwjack.
(5) Install converter-to-drive plate bolts and torque
to 88 N´m (65 ft. lbs.) torque.
(6) Install starter motor and tighten bolts to 54
N´m (40 ft. lbs.) torque. Make sure to fasten ground
cable to upper starter bolt as shown in (Fig. 52).
(7) Connect starter electrical harness and tighten
positive cable nut to 10 N´m (90 in. lbs.) torque.
(8) Install bellhousing dust cover (Fig. 51).
(9) Install left engine-to-transaxle bending brace
(Fig. 51).
(10) Install structural collar (Fig. 51) as follows:
(a) Position collar and install all bolts finger
tight.
(b) Tighten the collar-to-oil pan bolts to 3 N´m
(30 in. lbs.) torque.
Fig. 54 Transaxle Removal/Installation
1 ± CLIP
2 ± BOLT (3)3 ± TRANSAXLE
4 ± CONVERTER BOLT (4)
Fig. 55 Transaxle Upper Mount and Bracket
1 ± MOUNT
2 ± TRANSAXLE
PLTRANSAXLE 21 - 87
REMOVAL AND INSTALLATION (Continued)

CLEANING AND INSPECTION
VALVE BODY
Allow all parts to soak a few minutes in a suitable
clean solvent. Wash thoroughly and blow dry with
compressed air. Be sure all passages are clean and
free from obstructions.
Inspect manual and throttle valve operating levers
and shafts for being bent, worn or loose. If a lever is
loose on its shaft, it should be replaced. Do not
attempt to straighten bent levers.
Inspect all mating surfaces for burrs, nicks and
scratches. Minor blemishes may be removed with cro-
cus cloth, using only a very light pressure. Using a
straightedge, inspect all mating surfaces for warpage
or distortion. Slight distortion may be corrected,
using a surface plate. Be sure all metering holes in
steel plate are open. Using a penlight, inspect bores
in valve body for scores, scratches, pits, and irregu-
larities.
Inspect all valve springs for distortion and col-
lapsed coils. Inspect all valves and plugs for burrs,
nicks, and scores. Small nicks and scores may be
removed with crocus cloth, providing extreme care is
taken not to round off sharp edges. The sharpness of
these edges is vitally important. It prevents foreign
matter from lodging between valve and valve body.
This reduces the possibility of sticking. Inspect all
valves and plugs for freedom of operation in valve
body bores.
When bores, valves, and plugs are clean and dry,
the valves and plugs should fall freely in the bores.
The valve body bores do not change their dimensions
with use. Therefore, a valve body that was function-
ing properly when vehicle was new, will operate cor-
rectly if it is properly and thoroughly cleaned. There
is no need to replace a valve body unless it is dam-
aged in handling.
ADJUSTMENTS
GEARSHIFT CABLE
Normal operation of the Park/Neutral Position
Switch provides a quick check to confirm proper link-
age adjustment. The engine starter should only oper-
ate when the transaxle shift lever is in the PARK (P)
or NEUTRAL (N) positions.
If the engine starts in any other gear position, or
the vehicle rolls when the shifter is in gated PARK
(P), a gearshift cable adjustment is necessary.
ADJUSTMENT
(1) Loosen set screw and remove knob from shifter
handle (Fig. 214).(2) Remove the center console assembly as shown
in (Fig. 215).
(3)Adjust gearshift cable as follows:
(a) Place gearshift lever in the PARK (P) posi-
tion.
(b) Loosen shift cable adjustment screw (Fig.
216).
(c) Move transaxle manual lever to the PARK.
Verify transaxle is in PARK by attempting to roll
vehicle in either direction.
Fig. 214 Gearshift Knob Removal/Installation
1 ± SHIFTER KNOB
2 ± SET SCREW
Fig. 215 Center Console Removal/Installation
1 ± CONSOLE
2 ± SCREW (4)
3 ± SCREW (2)
PLTRANSAXLE 21 - 135

(M) Check Engine Lamp (MIL) will illuminate during engine operation if this Diagnostic Trouble Code was recorded.
P0325 Knock Sensor #1 Circuit Knock sensor (#1) signal above or below minimum
acceptable threshold voltage at particular engine
speeds.
P0330 Knock Sensor #2 Circuit Knock sensor (#2) signal above or below minimum
acceptable threshold voltage at particular engine
speeds.
P0340 (M) No Cam Signal At PCM No fuel sync
P0350 Ignition Coil Draws Too Much
CurrentA coil (1-5) is drawing too much current.
P0351 (M) Ignition Coil # 1 Primary Circuit Peak primary circuit current not achieved with maximum
dwell time.
P0352 (M) Ignition Coil # 2 Primary Circuit Peak primary circuit current not achieved with maximum
dwell time.
P0353 (M) Ignition Coil # 3 Primary Circuit Peak primary circuit current not achieved with maximum
dwell time.
P0354 (M) Ignition Coil # 4 Primary Circuit Peak primary circuit current not achieved with maximum
dwell time (High Impedance).
P0355 (M) Ignition Coil # 5 Primary Circuit Peak primary circuit current not achieved with maximum
dwell time (High Impedance).
P0356 (M) Ignition Coil # 6 Primary Circuit Peak primary circuit current not achieved with maximum
dwell time (high impedance).
P0357 Ignition Coil # 7 Primary Circuit Peak primary circuit current not achieved with maximum
dwell time (high impedance).
P0358 Ignition Coil # 8 Primary Circuit Peak primary circuit current not achieved with maximum
dwell time (high impedance).
P0401 (M) EGR System Failure Required change in air/fuel ration not detected during
diagnostic test.
P0403 (M) EGR Solenoid Circuit An open or shorted condition detected in the EGR
solenoid control circuit.
P0404 (M) EGR Position Sensor Rationality EGR position sensor signal does not correlate to EGR
duty cycle.
P0405 (M) EGR Position Sensor Volts Too Low EGR position sensor input below the acceptable voltage
range.
P0406 (M) EGR Position Sensor Volts Too
HighEGR position sensor input above the acceptable voltage
range.
P0412 Secondary Air Solenoid Circuit An open or shorted condition detected in the secondary
air (air switching/aspirator) solenoid control circuit.
P0420 (M) 1/1 Catalytic Converter Efficiency Catalyst 1/1 efficiency below required level.
P0432 (M) 1/2 Catalytic Converter Efficiency Catalyst 2/1 efficiency below required level.
P0441 (M) Evap Purge Flow Monitor Insufficient or excessive vapor flow detected during
evaporative emission system operation.
P0442 (M) Evap Leak Monitor Medium Leak
DetectedA small leak has been detected in the evaporative
system.
P0443 (M) Evap Purge Solenoid Circuit An open or shorted condition detected in the EVAP
purge solenoid control circuit.
P0455 (M) Evap Leak Monitor Large Leak
DetectedA large leak has been detected in the evaporative
system.
PLEMISSION CONTROL SYSTEMS 25 - 9
DESCRIPTION AND OPERATION (Continued)

(M) Check Engine Lamp (MIL) will illuminate during engine operation if this Diagnostic Trouble Code was recorded.
P0456 Evap Leak Monitor Small Leak
Detected
P0460 Fuel Level Unit No Change Over
MilesNo movement of fuel level sender detected.
P0461 Fuel Level Unit No Changeover
TimeNo level of fuel level sender detected.
P0462 Fuel Level Sending Unit Volts Too
LowFuel level sensor input below acceptable voltage.
P0463 Fuel Level Sending Unit Volts Too
HighFuel level sensor input above acceptable voltage.
P0500 (M) No Vehicle Speed Sensor Signal No vehicle speed sensor signal detected during road
load conditions.
P0505 (M) Idle Air Control Motor Circuits Replace
P0522 Oil Pressure Sens Low Oil pressure sensor input below acceptable voltage.
P0523 Oil Pressure Sens High Oil pressure sensor input above acceptable voltage.
P0551 (M) Power Steering Switch Failure Incorrect input state detected for the power steering
switch circuit. PL: High pressure seen at high speed.
P0600 (M) PCM Failure SPI Communications No communication detected between co-processors in
the control module.
P0601 (M) Internal Controller Failure Internal control module fault condition (check sum)
detected.
P0604 Internal Trans Controller Transmission control module RAM self test fault
detected. -Aisin transmission.
P0605 Internal Trans Controller Transmission control module ROM self test fault
detected -Aisin transmission.
P0622 (G) Generator Field Not Switching
ProperlyAn open or shorted condition detected in the generator
field control circuit.
P0645 A/C Clutch Relay Circuit An open or shorted condition detected in the A/C clutch
relay control circuit.
P0700 (M) EATX Controller DTC Present This SBEC III or JTEC DTC indicates that the EATX or
Aisin controller has an active fault and has illuminated
the MIL via a CCD (EATX) or SCI (Aisin) message. The
specific fault must be acquired from the EATX via CCD
or from the Aisin via ISO-9141.
P0703 (M) Brake Switch Stuck Pressed or
ReleasedIncorrect input state detected in the brake switch circuit.
(Changed from P1595).
P0711 Trans Temp Sensor, No Temp Rise
After StartRelationship between the transmission temperature and
overdrive operation and/or TCC operation indicates a
failure of the Transmission Temperature Sensor. OBD II
Rationality.
P0712 Trans Temp Sensor Voltage Too
LowTransmission fluid temperature sensor input below
acceptable voltage.
P0713 Trans Temp Sensor Voltage Too
HighTransmission fluid temperature sensor input above
acceptable voltage.
P0720 Low Output SPD Sensor RPM,
Above 15 MPHThe relationship between the Output Shaft Speed
Sensor and vehicle speed is not within acceptable
limits.
25 - 10 EMISSION CONTROL SYSTEMSPL
DESCRIPTION AND OPERATION (Continued)

MONITORED SYSTEMS
DESCRIPTION
There are new electronic circuit monitors that
check fuel, emission, engine and ignition perfor-
mance. These monitors use information from various
sensor circuits to indicate the overall operation of the
fuel, engine, ignition and emission systems and thus
the emissions performance of the vehicle.
The fuel, engine, ignition and emission systems
monitors do not indicate a specific component prob-
lem. They do indicate that there is an implied prob-
lem within one of the systems and that a specific
problem must be diagnosed.
If any of these monitors detect a problem affecting
vehicle emissions, the Malfunction Indicator (Check
Engine) Lamp will be illuminated. These monitors
generate Diagnostic Trouble Codes that can be dis-
played with the check engine lamp or a scan tool.
The following is a list of the monitored systems:
²EGR Monitor
²Misfire Monitor
²Fuel System Monitor
²Evaporative Emissions Monitor
Following is a description of each system monitor,
and its DTC.
Refer to the appropriate Powertrain Diagnos-
tics Procedures manual for diagnostic proce-
dures.
EGR MONITOR
The Powertrain Control Module (PCM) performs
an on-board diagnostic check of the EGR system.
The EGR system consists of two main components:
a vacuum solenoid back pressure transducer and a
vacuum operated valve. The EGR monitor is used to
test whether the EGR system is operating within
specifications. The diagnostic check activates only
during selected engine/driving conditions. When the
conditions are met, the EGR is turned off (solenoid
energized) and the O2S compensation control is mon-
itored. Turning off the EGR shifts the air fuel (A/F)
ratio in the lean direction. Oxygen sensor voltage
then indicates increased oxygen in the exhaust. Con-
sequently, Short Term Compensation shifts to rich
(increased injector pulse width). By monitoring the
shift, the PCM can indirectly monitor the EGR sys-
tem. While this test does not directly measure the
operation of the EGR system, it can be inferred from
the shift in the O2S data whether the EGR system is
operating correctly. Because the O2S is being used,
the O2S test must pass its test before the EGR test.
Enabling ConditionsÐ
²Engine Temperature
²Engine Run Time
²Engine RPM²MAP Sensor
²TPS
²Vehicle Speed
²Short Term Compensation
Pending ConditionsÐThe EGR Monitor does
not run when any of the following example faults
have illuminated the MIL:
²Misfire
²Oxygen Sensor Monitor
²Oxygen Sensor Heater Monitor
²Fuel System Rich/Lean
²Limp in for MAP, TPS or ECT
²Vehicle Speed Sensor
²Cam or Crank Sensor
²EGR Electrical
²EVAP Electrical
²Fuel Injector
²Ignition Coil
²Idle Speed
²Engine Coolant Temperature (ECT)
²MAP Sensor
²Intake Air Temperature (IAT)
Conflict ConditionsÐThe EGR Monitor typi-
cally does not run if any of the following conditions
are present:
²Fuel System Monitor
²Purge Monitor
²Catalyst Monitor
²Low Fuel Level
²High Altitude
²Low Ambient Air Temperature
The EGR Monitor does not run if any of the follow-
ing example DTCs are present:
²Misfire Monitor, Priority 2
²Upstream Oxygen Sensor Heater, Priority 1
²Fuel System Monitor, Priority 2
²Oxygen Sensor Monitor, Priority 1
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.
OBD II regulations for misfire monitoring require
two different tests for misfire. The first is a Catalyst
Damage level of misfire test. The second is for emis-
sions greater than 1.5 times the Federal Tailpipe
(FTP) standards. The tests are monitored by two dif-
ferent counters. These counters are:
PLEMISSION CONTROL SYSTEMS 25 - 15
DESCRIPTION AND OPERATION (Continued)

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 output. The programmed memory
acts as a self calibration tool that the engine control-
ler uses to compensate for variations in engine spec-
ifications, sensor tolerances and engine fatigue over
the life span of the engine. By monitoring the actual
air-fuel ratio with the O2S (short term) and multiply-
ing that with the program long-term (adaptive) mem-
ory and comparing that to the limit, it can be
determined whether it will pass an emissions test. If
a malfunction occurs such that the PCM cannot
maintain the optimum A/F ratio, then the MIL will
be illuminated.
Monitor OperationÐFuel systems monitors do
not have a pre-test because they are continuously
running monitors. Therefore, the PCM constantly
monitors Short Term Compensation and Long Term
Adaptive memory.
Lean: If at anytime during a lean engine operation,
short term compensation multiplied by long term
adaptive exceeds a certain percentage for an
extended period, the PCM sets a Fuel System Lean
Fault for that trip and a Freeze Frame is entered.
Rich: If at anytime during a rich operation, Short
Term Compensation multiplied by Long Term Adap-
tive is less than a predetermined value, the PCM
checks the Purge Free Cells.
Purge Free Cells are values placed in Adaptive
Memory cells when the EVAP Purge Solenoid is OFF.
Two, three or four Purge Free cells are used. One cor-
responds to an Adaptive Memory cell at idle, the
other to a cell that is off-idle. For example, if a Purge
Free cell is labeled PFC1, it would hold the value for
Adaptive Memory cell C1 under non-purge condi-
tions.
If all Purge Free Cells are less than a certain per-
centage, and the Adaptive Memory factor is less than
a certain percentage, the PCM sets a Fuel System
Rich fault for that trip and a Freeze Frame is
entered.
The Fuel Monitor is a two trip monitor. The PCM
records engine data in Freeze Frame upon setting of
the first fault, or maturing code. When the fuel mon-
itor fails on a second consecutive trip, the code is
matured and the MIL is illuminated. The stored
Freeze Frame data is still from the first fault.
In order for the PCM to extinguish the MIL, the
Fuel Monitor must pass in a Similar Condition Win-
dow. The similar conditions relate to RPM and load.
The engine must be within a predetermined percent-
age of both RPM and load when the monitor runs to
count a good trip. As with all DTCs, three good tripsare required to extinguish the MIL and 40 warm up
cycles are required to erase the DTC. If the engine
does not run in a Similar Conditions Window, the
Task Manager extinguishes the MIL after 80 good
trips.
Enabling ConditionsÐThe following conditions
must be met to operate the fuel control monitor:
²PCM not in fuel crank mode (engine running)
²PCM in Closed Loop fuel control
²Fuel system updating Long Term Adaptive
²Fuel level above 15% of capacity
²Fuel level below 85% of capacity
Pending ConditionsÐThe Fuel Control Monitor
does not operate if the MIL is illuminated for any of
the following:
²Misfire Monitor
²Upstream O2S
²EVAP Purge Solenoid Electrical PCM Self Test
Fault
²Camshaft or Crankshaft Position Sensor
²Fuel Injectors
²Ignition Coil Primary
²Throttle Position (TPS) Sensor
²Engine Coolant Temperature (ECT) Sensor
²Manifold Absolute Pressure (MAP) Sensor
²Idle Air Control (IAC)
²5V Output Too Low
²EGR Monitor
²EGR Solenoid Circuit
²Vehicle Speed Sensor
²Oxygen Sensor Monitor
²Oxygen Sensor Heater Monitor
²Oxygen Sensor Electrical
²Idle Speed Rationality
²Intake Air Temperature
SuspendÐThe Task Manager will suspend
maturing a Fuel System fault if any of the following
are present:
²Oxygen Sensor Response, Priority 1
²O2 Heater, Priority 1
²Misfire Monitor, Priority 2
EVAPORATIVE EMISSIONS MONITOR
LEAK DETECTION PUMP MONITORÐThe
leak detection assembly incorporates two primary
functions: it must detect a leak in the evaporative
system and seal the evaporative system so the leak
detection test can be run.
The primary components within the assembly are:
A three port solenoid that activates both of the func-
tions listed above; a pump which contains a switch,
two check valves and a spring/diaphragm, a canister
vent valve (CVV) seal which contains a spring loaded
vent seal valve.
PLEMISSION CONTROL SYSTEMS 25 - 17
DESCRIPTION AND OPERATION (Continued)

NOTE: Comprehensive component monitors are
continuous. Therefore, enabling conditions do not
apply.
Input RationalityÐWhile input signals to the
PCM are constantly being monitored for electrical
opens and shorts, they are also tested for rationality.
This means that the input signal is compared against
other inputs and information to see if it makes sense
under the current conditions.
PCM sensor inputs that are checked for rationality
include:
²Manifold Absolute Pressure (MAP) Sensor
²Oxygen Sensor (O2S)
²Engine Coolant Temperature (ECT) Sensor
²Camshaft Position (CMP) Sensor
²Vehicle Speed Sensor
²Crankshaft Position (CKP) Sensor
²Intake Air Temperature (IAT) Sensor
²Throttle Position (TPS) Sensor
²Ambient/Battery Temperature Sensors
²Power Steering Switch
²Oxygen Sensor Heater
²Engine Controller
²Brake Switch
²Leak Detection Pump Switch
²P/N Switch
²Trans Controls
Output FunctionalityÐPCM outputs are tested
for functionality in addition to testing for opens and
shorts. When the PCM provides a voltage to an out-
put component, it can verify that the command was
carried out by monitoring specific input signals for
expected changes. For example, when the PCM com-
mands the Idle Air Control (IAC) Motor to a specific
position under certain operating conditions, it expects
to see a specific (target) idle speed (RPM). If it does
not, it stores a DTC.
PCM outputs monitored for functionality include:
²Fuel Injectors
²Ignition Coils
²Torque Converter Clutch Solenoid
²Idle Air Control
²Purge Solenoid
²EGR Solenoid
²LDP Solenoid
²Radiator Fan Control
²Trans Controls
OXYGEN SENSOR (O2S) MONITOR
DESCRIPTIONÐEffective control of exhaust
emissions is achieved by an oxygen feedback system.
The most important element of the feedback system
is the O2S. The O2S is located in the exhaust path.
Once it reaches operating temperature 300É to 350ÉC
(572É to 662ÉF), the sensor generates a voltage that
is inversely proportional to the amount of oxygen inthe exhaust. When there is a large amount of oxygen
in the exhaust caused by a lean condition, the sensor
produces a low voltage, below 450 mV. When the oxy-
gen content is lower, caused by a rich condition, the
sensor produces a higher voltage, above 450mV.
The information obtained by the sensor is used to
calculate the fuel injector pulse width. This main-
tains a 14.7 to 1 air fuel (A/F) ratio. At this mixture
ratio, the catalyst works best to remove hydrocarbons
(HC), carbon monoxide (CO) and nitrous oxide (NOx)
from the exhaust.
The O2S is also the main sensing element for the
EGR, Catalyst and Fuel Monitors.
The O2S may fail in any or all of the following
manners:
²Slow response rate (Big Slope)
²Reduced output voltage (Half Cycle)
²Heater Performance
Slow Response Rate (Big Slope)ÐResponse
rate is the time required for the sensor to switch
from lean to rich signal output once it is exposed to a
richer than optimum A/F mixture or vice versa. As
the PCM adjusts the air/fuel ratio, the sensor must
be able to rapidly detect the change. As the sensor
ages, it could take longer to detect the changes in the
oxygen content of the exhaust gas. The rate of
change that an oxygen sensor experiences is called
'Big Slope'. The PCM checks the oxygen sensor volt-
age in increments of a few milliseconds.
Reduced Output Voltage (Half Cycle)ÐThe
output voltage of the O2S ranges from 0 to 1 volt. A
good sensor can easily generate any output voltage in
this range as it is exposed to different concentrations
of oxygen. To detect a shift in the A/F mixture (lean
or rich), the output voltage has to change beyond a
threshold value. A malfunctioning sensor could have
difficulty changing beyond the threshold value. Each
time the voltage signal surpasses the threshold, a
counter is incremented by one. This is called the Half
Cycle Counter.
Heater PerformanceÐThe heater is tested by a
separate monitor. Refer to the Oxygen Sensor Heater
Monitor.
OPERATIONÐAs the Oxygen Sensor signal
switches, the PCM monitors the half cycle and big
slope signals from the oxygen sensor. If during the
test neither counter reaches a predetermined value, a
malfunction is entered and a Freeze Frame is stored.
Only one counter reaching its predetermined value is
needed for the monitor to pass.
The Oxygen Sensor Monitor is a two trip monitor
that is tested only once per trip. When the Oxygen
Sensor fails the test in two consecutive trips, the
MIL is illuminated and a DTC is set. The MIL is
extinguished when the Oxygen Sensor monitor
passes in three consecutive trips. The DTC is erased
25 - 20 EMISSION CONTROL SYSTEMSPL
DESCRIPTION AND OPERATION (Continued)

from memory after 40 consecutive warm-up cycles
without test failure.
Enabling ConditionsÐThe following conditions
must typically be met for the PCM to run the oxygen
sensor monitor:
²Battery voltage
²Engine temperature
²Engine run time
²Engine run time at a predetermined speed
²Engine run time at a predetermined speed and
throttle opening
²Transmission in gear (automatic only)
²Fuel system in Closed Loop
²Long Term Adaptive (within parameters)
²Power Steering Switch in low PSI (no load)
²Engine at idle
²Fuel level above 15%
²Ambient air temperature
²Barometric pressure
²Engine RPM within acceptable range of desired
idle
²Closed throttle speed
Pending ConditionsÐThe Task Manager typi-
cally does not run the Oxygen Sensor Monitor if over-
lapping monitors are running or the MIL is
illuminated for any of the following:
²Misfire Monitor
²Front Oxygen Sensor and Heater Monitor
²MAP Sensor
²Vehicle Speed Sensor
²Engine Coolant Temperature Sensor
²Throttle Position Sensor
²Engine Controller Self Test Faults
²Cam or Crank Sensor
²Injector and Coil
²Idle Air Control Motor
²EVAP Electrical
²EGR Solenoid Electrical
²Intake Air Temperature
²5 Volt Feed
ConflictÐThe Task Manager does not run the
Oxygen Sensor Monitor if any of the following condi-
tions are present:
²A/C ON (A/C clutch cycling temporarily sus-
pends monitor)
²Purge flow in progress
SuspendÐThe Task Manager suspends maturing
a fault for the Oxygen Sensor Monitor if an of the fol-
lowing are present:
²Oxygen Sensor Heater Monitor, Priority 1
²Misfire Monitor, Priority 2
OXYGEN SENSOR HEATER MONITOR
DESCRIPTIONÐIf there is an oxygen sensor
(O2S) DTC as well as a O2S heater DTC, the O2S
fault MUST be repaired first. After the O2S fault isrepaired, verify that the heater circuit is operating
correctly.
The voltage readings taken from the O2S are very
temperature sensitive. The readings are not accurate
below 300ÉC. Heating of the O2S is done to allow the
engine controller to shift to closed loop control as
soon as possible. The heating element used to heat
the O2S must be tested to ensure that it is heating
the sensor properly.
The heater element itself is not tested. The sensor
output is used to test the heater by isolating the
effect of the heater element on the O2S output volt-
age from the other effects. The resistance is normally
between 100 ohms and 4.5 megaohms. When oxygen
sensor temperature increases, the resistance in the
internal circuit decreases. The PCM sends a 5 volts
biased signal through the oxygen sensors to ground
this monitoring circuit. As the temperature increases,
resistance decreases and the PCM detects a lower
voltage at the reference signal. Inversely, as the tem-
perature decreases, the resistance increases and the
PCM detects a higher voltage at the reference signal.
an The O2S circuit is monitored for a drop in voltage.
OPERATIONÐThe Oxygen Sensor Heater Moni-
tor begins after the ignition has been turned OFF
and the O2 sensors have cooled. The PCM sends a 5
volt bias to the oxygen sensor every 1.6 seconds. The
PCM keeps it biased for 35 ms each time. As the sen-
sor cools down, the resistance increases and the PCM
reads the increase in voltage. Once voltage has
increased to a predetermined amount, higher than
when the test started, the oxygen sensor is cool
enough to test heater operation.
When the oxygen sensor is cool enough, the PCM
energizes the ASD relay. Voltage to the O2 sensor
begins to increase the temperature. As the sensor
temperature increases, the internal resistance
decreases. The PCM continues biasing the 5 volt sig-
nal to the sensor. Each time the signal is biased, the
PCM reads a voltage decrease. When the PCM
detects a voltage decrease of a predetermined value
for several biased pulses, the test passes.
The heater elements are tested each time the
engine is turned OFF if all the enabling conditions
are met. If the monitor fails, the PCM stores a
maturing fault and a Freeze Frame is entered. If two
consecutive tests fail, a DTC is stored. Because the
ignition is OFF, the MIL is illuminated at the begin-
ning of the next key cycle.
Enabling ConditionsÐThe following conditions
must be met for the PCM to run the oxygen sensor
heater test:
²Engine run time of at least 5.1 minutes
²Key OFF power down
²Battery voltage of at least 10 volts
²Sufficient Oxygen Sensor cool down
PLEMISSION CONTROL SYSTEMS 25 - 21
DESCRIPTION AND OPERATION (Continued)