2000 DODGE NEON transmission oil

CONDITION POSSIBLE CAUSES CORRECTION
NO DRIVE RANGE
(REVERSE OK)1. Fluid Level Low. 1. Add fluid and check for leaks if drive is
restored.
2. Gearshift Linkage/Cable
Loose/Misadjusted.2. Repair or replace linkage components.
3. Rear Clutch Burnt. 3. Remove and disassemble transmission
and rear clutch and seals. Repair/replace
worn or damaged parts as needed.
4. Valve Body Malfunction. 4. Remove and disassemble valve body.
Replace assembly if any valves or bores
are damaged.
5. Transmission Overrunning Clutch
Broken.5. Remove and disassemble transmission.
Replace overrunning clutch.
6. Input Shaft Seal Rings Worn/
Damaged.6. Remove and disassemble transmission.
Replace seal rings and any other worn or
damaged parts.
7. Front Planetary Failed Broken. 7. Remove and repair.
NO DRIVE OR REVERSE
(VEHICLE WILL NOT
MOVE)1. Fluid Level Low. 1. Add fluid and check for leaks if drive is
restored.
2. Gearshift Linkage/Cable
Loose/Misadjusted.2. Inspect, adjust and reassemble linkage
as needed. Replace worn/damaged parts.
3. Filter Plugged. 3. Remove and disassemble transmission.
Repair or replace failed components as
needed. Replace filter. If filter and fluid
contained clutch material or metal particles,
an overhaul may be necessary. Perform
lube flow test. Flush oil. Replace cooler as
necessary.
4. Oil Pump Damaged. 4. Perform pressure test to confirm low
pressure. Replace pump body assembly if
necessary.
5. Valve Body Malfunctioned. 5. Check press and inspect valve body.
Replace valve body (as assembly) if any
valve or bore is damaged. Clean and
reassemble correctly if all parts are in good
condition.
6. Transmission Internal Component
Damaged.6. Remove and disassemble transmission.
Repair or replace failed components as
needed. Remove and disassemble
transmission. Repair or replace failed
components as needed.
7. Park Sprag not Releasing - Check
Stall Speed, Worn/Damaged/Stuck.7. Remove, disassemble, repair.
8. Torque Converter Damage. 8. Inspect and replace as required.
21 - 60 TRANSAXLEPL
DIAGNOSIS AND TESTING (Continued)

LOW AND REVERSE SERVO (REAR)
Direct air pressure into LOW/REVERSE SERVO
APPLY passage. Operation of servo is indicated by a
tightening of rear band. Spring tension on servo pis-
ton should release the band.
If clutches and servos operate properly, no upshift
indicates that a malfunction exists in the valve body.
FLUID LEAKAGE-TRANSAXLE TORQUE
CONVERTER HOUSING AREA
(1) Check for source of leakage.
(2) Since fluid leakage near the torque converter
area may be from an engine oil leak, the area should
be checked closely. Factory fill fluid is dyed red and,
therefore, can be distinguished from engine oil.
(3) Prior to removing the transaxle, perform the
following checks:
(4) When leakage is determined to originate from
the transaxle, check fluid level prior to removal of
the transaxle and torque converter.
(5) High oil level can result in oil leakage out the
vent in the dipstick. If the fluid level is high, adjust
to proper level.
(6) After performing this operation, inspect for
leakage. If a leak persists, perform the following
operation on the vehicle. This will determine if the
torque converter or transaxle is leaking.
TORQUE CONVERTER LEAKAGE
Possible sources of torque converter leakage are:
²Torque converter weld leaks at the outside diam-
eter (peripheral) weld
²Torque converter hub weld
²Torque converter impeller shell cracked adjacent
to hub
²At drive lug welds
NOTE: Hub weld is inside and not visible. Do not
attempt to repair. Replace torque converter.
BRAKE TRANSMISSION SHIFT INTERLOCK
The following chart describes the normal operation
of the Brake Transmission Shift Interlock (BTSI) sys-
tem. If the ªexpected responseº differs from the vehi-
cle's response, then system repair and/or adjustment
is necessary. Refer to Brake Transmission Interlock
Removal and Installation or Adjustment in this
Group.
SERVICE PROCEDURES
TRANSAXLE FLUID AND FILTER SERVICE
NOTE: Refer to Group 0, Lubrication and Mainte-
nance, or the vehicle owner's manual, for the rec-
ommended maintenance (fluid/filter change)
intervals for this transaxle.
NOTE: Only fluids of the type labeled MoparT
ATF+4 (Automatic Transmission Fluid) Type 9602
should be used. A filter change should be made at
the time of the transmission oil change. The magnet
(on the inside of the oil pan) should also be cleaned
with a clean, dry cloth.
NOTE: If the transaxle is disassembled for any rea-
son, the fluid and filter should be changed.
FLUID/FILTER SERVICE (RECOMMENDED)
(1) Raise vehicle on a hoist (See Lubrication,
Group 0). Place a drain container with a large open-
ing, under transaxle oil pan.
(2) Loosen pan bolts and tap the pan at one corner
to break it loose allowing fluid to drain, then remove
the oil pan.
(3) Install a new filter and o-ring on bottom of the
valve body and tighten retaining screws to 5 N´m (40
in. lbs.).
ACTION EXPECTED RESPONSE
1. Turn key to the ªOFFº
position.1. Shifter CAN be shifted
out of park.
2. Turn key to the
9ON/RUNº position.2. Shifter CANNOT be
shifted out of park.
3. Turn key to the
ªON/RUNº position and
depress the brake pedal.3. Shifter CAN be shifted
out of park.
4. Leave shifter in any
gear and try to return key
to the ªLOCKº or9ACCº
position.4. Key cannot be
returned to the ªLOCKº or
ªACCº position.
5. Return shifter to
ªPARKº and try to remove
the key.5. Key can be removed
(after returning to ªLOCKº
position).
6. With the key removed,
try to shift out of ªPARKº.6. Shifter cannot be
shifted out of ªPARKº.
NOTE: Any failure to meet these expected
responses requires system adjustment or repair.
21 - 70 TRANSAXLEPL
DIAGNOSIS AND TESTING (Continued)

(4) Clean the oil pan and magnet. Reinstall pan
using new Mopar Silicone Adhesive sealant. Tighten
oil pan bolts to 19 N´m (165 in. lbs.).
(5) Pour four quarts of MopartATF+4 (Automatic
Transmission Fluid) Type 9602 through the dipstick
opening.
(6) Start engine and allow to idle for at least one
minute. Then, with parking and service brakes
applied, move selector lever momentarily to each
position, ending in the park or neutral position.
(7) Check the transaxle fluid level and add an
appropriate amount to bring the transaxle fluid level
to 3mm (1/8 in.) below the ªADDº mark on the dip-
stick (Fig. 8).
(8) Recheck the fluid level after the transaxle has
reached normal operating temperature (180ÉF.).
(9) To prevent dirt from entering transaxle, make
certain that dipstick is fully seated into the dipstick
opening.
ALTERNATIVE MAINTENANCE METHODS
TRANSAXLE FLUID EXCHANGER METHOD
CAUTION: The use of any fluid exchanger that
introduces additives into the transaxle is not rec-
ommended.
(1) To perform the transaxle fluid exchange, the
transaxle must be at operating temperature. Drive
the vehicle until it reaches full operating tempera-
ture.
(2) Obtain a suitable transaxle fluid exchanger
and verify the tank is clean and dry.
(3) Fill the tank to the recommended fill capacity
with MopartATF+4 Type 9602.
(4) Connect the machine to the vehicle following
the manufacturers instructions. Perform the
exchange procedure following the instructions pro-
vided with the machine.(5) Once machine has completed the fluid
exchange. Check the fluid level and condition and fill
to proper level with MopartATF+4 Type 9602. Refer
to Fluid Level and Condition Check in this group for
the proper fluid ªtop-offº procedure.
NOTE: Verify that the transaxle cooler lines are
tightened to proper specifications. Cooler line
torque specification is 2 N²m (18 in. lbs.).
DIPSTICK TUBE FLUID SUCTION METHOD
(1) When performing the fluid suction method,
make sure the transaxle is at full operating temper-
ature.
(2) To perform the dipstick tube fluid suction
method, use a suitable fluid suction device (Vaculay
or equivalent).
(3) Insert the fluid suction line into the dipstick
tube.
NOTE: Verify that the suction line is inserted to the
lowest point of the transaxle oil pan. This will
ensure complete evacuation of the fluid in the pan.
(4) Follow the manufacturers recommended proce-
dure and evacuate the fluid from the transaxle.
(5) Remove the suction line from the dipstick tube.
(6) Pour four quarts of MopartATF+4 (Automatic
Transmission Fluid) Type 9602 through the dipstick
opening.
(7) Start engine and allow to idle for at least one
minute. Then, with parking and service brakes
applied, move selector lever momentarily to each
position, ending in the park or neutral position.
(8) Check the transaxle fluid level and add an
appropriate amount to bring the transaxle fluid level
to 3mm (1/8 in.) below the ªADDº mark on the dip-
stick (Fig. 8).
(9) Recheck the fluid level after the transaxle has
reached normal operating temperature (180ÉF.).
(10) To prevent dirt from entering transaxle, make
certain that dipstick is fully seated into the dipstick
opening.
ALUMINUM THREAD REPAIR
Damaged or worn threads in the aluminum tran-
saxle case and valve body can be repaired by the use
of Heli-Coils. This repair consists of drilling out the
worn-out or damaged threads. Then tap the hole with
a Heli-Coil tap, and install a Heli-Coil insert into the
hole. This brings the hole back to its original thread
size.
Heli-Coil tools and inserts are readily available
from most automotive parts suppliers.
Fig. 8 Dipstick Markings
1 ± TRANSAXLE DIPSTICK
PLTRANSAXLE 21 - 71
SERVICE PROCEDURES (Continued)

FLUSHING COOLERS AND TUBES
When a transaxle failure has contaminated the
fluid, the transaxle oil cooler(s) must be flushed (both
radiator and remote). The cooler bypass valve in the
transaxle must be replaced also. The torque con-
verter must also be replaced with an exchange unit.
This will ensure that metal particles or sludged oil
are not later transferred back into the reconditioned
(or replaced) transaxle.
The recommended procedure for flushing the cool-
ers and tubes is to use Tool 6906A Cooler Flusher.
WARNING: WEAR PROTECTIVE EYEWEAR THAT
MEETS THE REQUIREMENTS OF OSHA AND ANSI
Z87.1±1968. WEAR STANDARD INDUSTRIAL RUB-
BER GLOVES.
KEEP LIT CIGARETTES, SPARKS, FLAMES, AND
OTHER IGNITION SOURCES AWAY FROM THE
AREA TO PREVENT THE IGNITION OF COMBUSTI-
BLE LIQUIDS AND GASES. KEEP A CLASS (B) FIRE
EXTINGUISHER IN THE AREA WHERE THE
FLUSHER WILL BE USED.
KEEP THE AREA WELL VENTILATED.
DO NOT LET FLUSHING SOLVENT COME IN CON-
TACT WITH YOUR EYES OR SKIN: IF EYE CONTAM-
INATION OCCURS, FLUSH EYES WITH WATER FOR
15 TO 20 SECONDS. REMOVE CONTAMINATED
CLOTHING AND WASH AFFECTED SKIN WITH
SOAP AND WATER. SEEK MEDICAL ATTENTION.
COOLER FLUSH USING TOOL 6906A
(1) Remove cover plate filler plug on Tool 6906A.
Fill reservoir 1/2 to 3/4 full of fresh flushing solution.
Flushing solvents are petroleum based solutions gen-
erally used to clean automatic transmission compo-
nents.DO NOTuse solvents containing acids, water,
gasoline, or any other corrosive liquids.
(2) Reinstall filler plug on Tool 6906A.
(3) Verify pump power switch is turned OFF. Con-
nect red alligator clip to positive (+) battery post.
Connect black (-) alligator clip to a good ground.
(4) Disconnect the cooler lines at the transmission.
NOTE: When flushing transmission cooler and
lines, ALWAYS reverse flush.
(5) Connect the BLUE pressure line to the OUT-
LET (From) cooler line.
(6) Connect the CLEAR return line to the INLET
(To) cooler line
(7) Turn pump ON for two to three minutes to
flush cooler(s) and lines. Monitor pressure readingsand clear return lines. Pressure readings should sta-
bilize below 20 psi. for vehicles equipped with a sin-
gle cooler and 30 psi. for vehicles equipped with dual
coolers. If flow is intermittent or exceeds these pres-
sures, replace cooler.
(8) Turn pump OFF.
(9) Disconnect CLEAR suction line from reservoir
at cover plate. Disconnect CLEAR return line at
cover plate, and place it in a drain pan.
(10) Turn pump ON for 30 seconds to purge flush-
ing solution from cooler and lines. Turn pump OFF.
(11) Place CLEAR suction line into a one quart
container of MopartATF+4 (Automatic Transmission
Fluid) Type 9602.
(12) Turn pump ON until all transmission fluid is
removed from the one quart container and lines. This
purges any residual cleaning solvent from the trans-
mission cooler and lines. Turn pump OFF.
(13) Disconnect alligator clips from battery. Recon-
nect flusher lines to cover plate, and remove flushing
adapters from cooler lines.
OIL PUMP VOLUME CHECK
After the new or repaired transmission has been
installed, fill to the proper level with MopartATF+4
(Automatic Transmission Fluid) Type 9602. The vol-
ume should be checked using the following proce-
dure:
(1) Disconnect theFrom coolerline at the trans-
mission and place a collecting container under the
disconnected line.
CAUTION: With the fluid set at the proper level,
fluid collection should not exceed (1) quart or inter-
nal damage to the transmission may occur.
(2) Run the engineat curb idle speed, with the
shift selector in neutral.
(3) If fluid flow is intermittent or it takes more
than 20 seconds to collect one quart of ATF, discon-
nect theTo Coolerline at the transaxle.
(4) Refill the transaxle to proper level and recheck
pump volume.
(5) If flow is found to be within acceptable limits,
replace the cooler. Then fill transmission to the
proper level, using MopartATF+4 (Automatic Trans-
mission Fluid) Type 9602.
(6) If fluid flow is still found to be inadequate,
check the line pressure using the Transaxle Hydrau-
lic Pressure Test procedure.
21 - 72 TRANSAXLEPL
SERVICE PROCEDURES (Continued)

SPECIFICATIONS
31TH AUTOMATIC TRANSAXLE
Type .........Automatic three speed with torque
converter and integral differential
Torque Converter Diameter...... 241millimeters
(9.48 in.)
OilType .....................MopartATF+4
(Automatic Transmission Fluid) Type 9602
Cooling Method.... Water Heat Exchanger and/or
air to oil heat exchanger
Lubrication . . . Pump (internal-external gear-type)
Transmission Gear Ratios
First Gear............................2.69
Second Gear...........................1.55
Third Gear............................1.00
Reverse Gear..........................2.10
Band Adjustment
KickdownÐBacked Off From 8 N²m
(72 in. lbs.).................... 21/4Turns
Low-ReverseÐBacked Off From 5 N²m
(41 in. lbs.).................... 31/2Turns
Clutch Pack Clearances
Front Clutch (Not Adjustable)......1.27-2.79mm
(0.050-0.110 in.)
Rear Clutch.......0.71-1.10mm (0.028-0.043 in.)
End Play
Input Shaft........0.19±1.50 mm (.008±.060 in.)
Front Clutch Retainer...........0.76±2.69 mm
(.030±.106 in.)
Front Carrier.......0.89±1.45 mm (.007±.057 in.)
Front Annulus Gear . . 0.09±0.50 mm (.0035±.020 in.)
Planet Pinion.......0.15±0.59 mm (.006±.023 in.)
Reverse Drum......0.76±3.36 mm (.030±.132 in.)
Oil Pump Clearances
Outer Gear To Pocket...........0.045-0.141mm
(0.0018-0.0056 in.)
Outer Gear Side Clearance.......0.020-0.046mm
(0.0008-0.0018 in.)
Inner Gear Side Clearance.......0.020-0.046mm
(0.0008-0.0018 in.)
Tapered Roller Bearing Settings
Differential Assembly . . 6 to 12 in. lbs. Drag Torque
Output Hub.......... 0to3in.lbs. Drag Torque
Transfer Shaft.......0.002 to 0.010 in. End Play
Overall Drag At Output
Hub ............. 3to16in.lbs. Drag TorqueThrust Washers
Reaction Shaft Support (No. 1).....1.55±1.60 mm
(.061±.063 in.)
Rear Clutch Retainer (No. 2)......1.55±1.60 mm
(.061±.063 in.)
Output Shaft (No. 3) (Select)......1.98±2.03 mm
(.077±.080 in.)
Output Shaft (No. 3) (Select)......2.15±2.22 mm
(.085±.087 in.)
Output Shaft (No. 3) (Select)......2.34±2.41 mm
(.092±.095 in.)
Front Annulus (No. 4)............2.95±3.05 mm
(.116±.120 in.)
Front Carrier (Nos. 5&6).........1.22±1.28 mm
(.0948±.050 in.)
Sun Gear-Front (No. 7)...........0.85±0.91 mm
(.033±.036 in.)
Sun Gear-Rear (No. 8)...........0.85±0.91 mm
(.033±.036 in.)
Rear Carrier (Nos. 9&10).........1.22±1.28 mm
(.0948±.050 in.)
Rev. Drum (No. 11) . . 1.55±1.60 mm (.061±.063 in.)
31TH TRANSAXLE TORQUE SPECIFICATIONS
DESCRIPTION TORQUE
Bell Housing Cover Bolts.... 12N´m(105 in. lbs.)
Cooler Line Clamps.......... 2N´m(18in.lbs.)
Diff. Bear. Ret. To Case Bolt . . 34 N´m (300 in. lbs.)
Diff. Cover To Case Bolt..... 19N´m(165 in. lbs.)
Exten. Hous. To Case Bolt . . . 28 N´m (250 in. lbs.)
Drive Plate To Crankshaft
Bolts................... 95N´m(70ft.lbs.)
Drive Plate To Torque Conv.
Bolts................... 88N´m(65ft.lbs.)
Fluid Filter Screw........... 5N´m(45in.lbs.)
Governor Counterweight
Screw................. 28N´m(250 in. lbs.)
Governor To Support Bolt...... 7N´m(60in.lbs.)
Kickdown Band Adj. Lock Nut . . 47 N´m (35 ft. lbs.)
Left Motor Mount Bolts....... 54N´m(40ft.lbs.)
Manual Cable To Trans.
Case Bolt.............. 28N´m(250 in. lbs.)
Manual Control Lever Screw . . 12 N´m (105 in. lbs.)
Oil Pan To Trans. Case
Screw................. 19N´m(165 in. lbs.)
Output Gear Strap Bolts...... 23N´m(17ft.lbs.)
Output Shaft Nut......... 271N´m(200 ft. lbs.)
Park/Neutral Switch......... 34N´m(25ft.lbs.)
Pressure Check Plug......... 5N´m(45in.lbs.)
Pump To Case Bolts........ 31N´m(275 in. lbs.)
Reaction Shaft Assembly
Bolt................... 28N´m(250 in. lbs.)
Rear Cover To Case Screw . . . 19 N´m (165 in. lbs.)
Reverse Band Adj. Lock Nut . . 14 N´m (125 in. lbs.)
21 - 150 TRANSAXLEPL

(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)

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)