1999 DODGE NEON Engine Coolant Temperature Sensor

1
K4
20
BK/LBK4
20
BK/LBK4
18
BK/LB
10C161
K4
20
BK/LB
POWERTRAIN
CONTROL
MODULE
43C1
1
SENSOR POSITION
THROTTLE
BK/LB20 K4
K4
20
BK/LB
CAMSHAFT
POSITION
SENSOR
2A
BK/LB18 K4
K4
20
BK/LB
2
SENSOR KNOCK
K4
20
BK/LB
11
BK/RD20 K4
S110
S120
S118
3
BK/LB20 K4
K4
20
BK/LB
3 2
SENSOR POSITION
CRANKSHAFT
BK/LB20 K4
K4
18
BK/LB
VEHICLE
SPEED
SENSOR
2
UPSTREAM
HEATED
OXYGEN
SENSOR
K4
18
BK/LBSENSOR MAP
IAT/
* 3
* DOHC 5
BK/LB20 K4
BUILT-UP-EXPORT) (EXCEPT
SENSOR
TEMPERATURE
BATTERY
(2.0L) SENSOR
OXYGEN
HEATED
DOWNSTREAM (SOHC) (1.8L/2.0L)
SENSOR
TEMPERATURE
COOLANT
ENGINE ENGINE
COOLANT
TEMPERATURE
SENSOR
(2.0L)
(DOHC)
2C170
(BUILT-UP-EXPORT) IMMOBILIZER
(8W-30-6)
(8W-30-3) (8W-30-8) (8W-30-7)(8W-30-6)
(8W-30-7) (8W-30-6)(8W-30-3)
(8W-30-7)
(8W-30-3) (8W-30-7) (8W-30-7)(8W-61-8)
PL8W-70 SPLICE INFORMATION 8W - 70 - 3
8356J988W-1

8W-80 CONNECTOR PIN-OUTS
Component Page
A/C Compressor Clutch.................8W-80-4
A/C Cycling Switch....................8W-80-4
A/C Heater Blower Motor...............8W-80-4
A/C Heater Control....................8W-80-4
A/C High Pressure Switch..............8W-80-4
A/C Low Pressure Switch...............8W-80-5
Airbag Control Module.................8W-80-5
Ash Receiver Lamp....................8W-80-6
Back-Up Lamp Switch.................8W-80-6
Battery Temperature Sensor.............8W-80-6
Blower Motor Resistor Block.............8W-80-6
Brake Warning Lamp Switch............8W-80-6
C101...............................8W-80-7
C102...............................8W-80-7
C103...............................8W-80-7
C104...............................8W-80-8
C105...............................8W-80-8
C108...............................8W-80-8
C160...............................8W-80-8
C161...............................8W-80-8
C170...............................8W-80-9
C205...............................8W-80-9
C206..............................8W-80-10
C225..............................8W-80-10
C230..............................8W-80-10
C231..............................8W-80-11
C241..............................8W-80-12
C242..............................8W-80-12
C301..............................8W-80-12
C303..............................8W-80-12
C309..............................8W-80-12
C340..............................8W-80-13
C341..............................8W-80-13
Camshaft Position Sensor..............8W-80-14
Center High Mounted Stop Lamp........8W-80-14
Cigar Lighter/Power Outlet.............8W-80-14
Clockspring.........................8W-80-14
Clutch Pedal Position Switch...........8W-80-15
Controller Anti-Lock Brake.............8W-80-15
Crankshaft Position Sensor.............8W-80-16
Data Link Connector..................8W-80-1
Daytime Running Lamp Module.........8W-80-16Component Page
Dome Lamp........................8W-80-17
Downstream Heated Oxygen Sensor......8W-80-17
Driver Door Lock Motor...............8W-80-17
Driver Door Lock Switch...............8W-80-17
Driver Power Window Motor............8W-80-17
Driver Power Window Switch...........8W-80-18
Driver Side Airbag...................8W-80-18
Duty Cycle Evap/Purge Solenoid.........8W-80-18
EGR Transducer Solenoid..............8W-80-19
Engine Coolant Temperature Sensor......8W-80-18
Engine Oil Pressure Switch............8W-80-19
Fog Lamp Switch....................8W-80-19
Front Fog Lamp Switch...............8W-80-19
Fuel Injector No. 1...................8W-80-19
Fuel Injector No. 2...................8W-80-19
Fuel Injector No. 3...................8W-80-20
Fuel Injector No. 4...................8W-80-20
Fuel Pump Module...................8W-80-20
Generator..........................8W-80-20
Glove Box Lamp And Switch............8W-80-20
Halo Lamp.........................8W-80-21
Headlamp Dimmer And Optical
Horn Switch......................8W-80-21
Headlamp Leveling Switch.............8W-80-21
Headlamp Switch....................8W-80-21
Heater Blower Motor.................8W-80-21
High Speed Warning Module...........8W-80-22
Horn..............................8W-80-22
Horn No. 1.........................8W-80-22
Horn No. 2.........................8W-80-22
IAT/Map Sensor.....................8W-80-25
Idle Air Control Motor.................8W-80-22
Ignition Coil Pack....................8W-80-22
Ignition Switch......................8W-80-23
Immobilizer.........................8W-80-23
Immobilizer Engine Sensor.............8W-80-23
Instrument Cluster-C1................8W-80-24
Instrument Cluster-C2................8W-80-24
Intermittent Wipe/Wash Switch.........8W-80-25
Key-In Switch.......................8W-80-25
Knock Sensor.......................8W-80-25
PL8W - 80 CONNECTOR PIN-OUTS 8W - 80 - 1

CAV CIRCUIT FUNCTION
1 K52 20PK/BK DUTY CYCLE EVAP/PURGE SOLENOID CONTROL
2 F12 20DG/WT FUSED IGNITION SWITCH OUTPUT (ST-RUN)
CAV CIRCUIT FUNCTION
1 K4 20BK/LB * SENSOR GROUND
1 K4 20BK/RD ** SENSOR GROUND
2 K2 20TN/DB * ENGINE COOLANT TEMPERATURE SENSOR SIGNAL
2 K2 20TN/BK ** ENGINE COOLANT TEMPERATURE SENSOR SIGNAL
3 G20 20VT/YL ENGINE COOLANT TEMPERATURE GAUGE SIGNAL
BLACK
2 1
3
* 1.8L/2.0L SOHC
** 2.0L DOHC
1
BLACK
2
6 4 25 3 1
NATURAL
UP FRONT LEFT 14LB Q11 6DOWN FRONT LEFT 14WT Q21 5
(ST-RUN) OUTPUT SWITCH IGNITION FUSED 14TN F21 4
GROUND 14BK/VT Z8 3
UP FRONT RIGHT SWITCH MASTER 14BR/WT Q16 2
DOWN FRONT RIGHT SWITCH MASTER 14VT/WT Q26 1
FUNCTION CIRCUIT CAV
CAV CIRCUIT FUNCTION
1 Q21 14WT RIGHT FRONT DOWN
2 Q11 14WT RIGHT FRONT UP
3 Z8 14BK/VT GROUND
4 F21 14TN FUSED IGNITION SWITCH OUTPUT (ST-RUN)
5 Q26 14VT/WT LEFT FRONT DOWN
6 Q16 14BR/WT LEFT FRONT UP
NATURAL1 3 5
24 6
DRIVER
POWER WINDOW
SWITCH (RHD) SWITCH (LHD) POWER WINDOWDRIVER
DUTY CYCLE
EVAP/PURGE
SOLENOID
ENGINE COOLANT
TEMPERATURE (ECT)
SENSOR
1 2
AIRBAG DRIVER SIDE
YELLOW
1 LINE SQUIB AIRBAG DRIVER 18BK/LB R43 22 LINE SQUIB AIRBAG DRIVER 18DG/LB R45 1
FUNCTION CIRCUIT CAV
8W - 80 - 18 8W-80 CONNECTOR PIN-OUTSPL
J988W-1PL008018

CAV CIRCUIT FUNCTION
1- -
2 K19 18BK/GY IGNITION COIL NO. 1, 3 DRIVER
3 K17 18DB/TN IGNITION COIL NO. 2, 4 DRIVER
4 K20 18DG GENERATOR FIELD DRIVER
5 V32 20YL/RD SPEED CONTROL FEED
6 A142 18DG/OR AUTOMATIC SHUT DOWN RELAY OUTPUT
7 K13 18YL/WT FUEL INJECTOR NO. 3 DRIVER
8 G3 20BK/PK CHECK ENGINE LAMP DRIVER
9- -
10 Z12 18BK/TN GROUND
11 - -
12 - -
13 K11 18WT/DB FUEL INJECTOR NO. 1 DRIVER
14 - -
15 - -
16 K14 18LB/BR
17 K12 18TN
18 K173 20LG
19 - -
20F12 18DB/WT FUSED IGNITION SWITCH OUTPUT (ST-RUN)
21 - -
22 - -
23 G4 20DB FUEL LEVEL SENSOR SIGNAL
24 K42 20BK/LG** KNOCK SENSOR SIGNAL
24 K42 20DB/LG** KNOCK SENSOR SIGNAL
31 40
21 30
11 20
110
BLACK
CONTROL SOLENOID RECIRCULATION GAS EXHAUST 20GY/YL K35 40- - 39
SENSE SWITCH A/C 18BR/OR C20 38
SIGNAL SENSOR POSITION THROTTLE 20OR/DB K22 35
- - 34
SIGNAL SENSOR POSITION CAMSHAFT 20TN/YL K44 33
SIGNAL SENSOR POSITION CRANKSHAFT 20GY/BK K24 32
- - 31
SIGNAL SENSOR OXYGEN HEATED UPSTREAM 20BK/DG K41 30
- - 29
- - 28
- - 27
SIGNAL SENSOR TEMPERATURE COOLANT ENGINE 20TN/BK** K2 26
SIGNAL SENSOR TEMPERATURE COOLANT ENGINE 20TN/DB* K2 26
- - 25
POWERTRAIN
CONTROL
MODULE - C2
20DB/WT F12 (ST-RUN)OUTPUT SWITCH IGNITION FUSED
24K42 20DB/LG KNOCK SENSOR SIGNAL
* 1.8L/2.0L SOHC
** 2.0L DOHC
1.8L
2.0L 36 K1 20DG/RD MANIFOLD ABSOLUTE PRESSURE SENSOR SIGNAL
37 K21 20BK/RD INTAKE AIR TEMPERATURE SENSOR SIGNAL
FUEL INJECTOR NO. 4 DRIVER
FUEL INJECTOR NO. 2 DRIVER
SOLID STATE RELAY CONTROL
8W - 80 - 34 8W-80 CONNECTOR PIN-OUTSPL
J988W-1PL008034

INTAKE MANIFOLDÐDOHC ENGINE
REMOVAL
WARNING: RELEASE FUEL SYSTEM PRESSURE
BEFORE SERVICING FUEL SYSTEM COMPONENTS.
SERVICE VEHICLES IN WELL VENTILATED AREAS
AND AVOID IGNITION SOURCES. NEVER SMOKE
WHILE SERVICING THE VEHICLE.
(1) Disconnect negative cable from battery.
(2) Remove fuel filler cap.
(3) Loosen wing nut on intake and remove fresh
air inlet duct (Fig. 23).
(4) Remove the protective cap from the fuel pres-
sure test port on the fuel rail (Fig. 21).
(5) Place the open end of fuel pressure release
hose, Special Tool C-4799-1, into an approved gaso-
line container. Connect the other end of hose to the
fuel pressure test port (Fig. 22). Fuel pressure will
bleed off through the hose into the gasoline con-
tainer. Fuel gauge C-4799-A contains hose C-4799-1.
(6) Disconnect the fuel supply line quick-connect at
the fuel tube assembly.
(7) Remove clean air inlet duct.WARNING: WRAP SHOP TOWELS AROUND HOSE
TO CATCH ANY GASOLINE SPILLAGE.
(8) Disconnect the coolant temperature sensor
(Fig. 24).
(9) Disconnect heater hose from intake manifold.
(10) Disconnect heater tube from bottom of intake
manifold.
(11) Disconnect upper radiator hose and coolant
recovery hose.
(12) Remove fuel rail assembly attaching screws
and remove fuel rail assembly from engine. Cover
injector holes with suitable covering.
CAUTION: Do not set fuel injectors on their tips,
damage may occur to the injectors
Fig. 21 Fuel Pressure Test PortÐTypical
Fig. 22 Releasing Fuel PressureÐTypical
Fig. 23 Fresh Air Inlet Duct
Fig. 24 Engine Coolant Temperature Sensor
PLEXHAUST SYSTEM AND INTAKE MANIFOLD 11 - 9
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)

FUEL INJECTION SYSTEM
INDEX
page page
GENERAL INFORMATION
INTRODUCTION......................... 21
MODES OF OPERATION.................. 21
DESCRIPTION AND OPERATION
AIR CONDITIONING CLUTCH RELAYÐ
PCM OUTPUT......................... 31
AIR CONDITIONING PRESSURE
TRANSDUCERÐPCM INPUT............. 25
AUTOMATIC SHUTDOWN (ASD) SENSEÐ
PCM INPUT........................... 25
AUTOMATIC SHUTDOWN RELAYÐ
PCM OUTPUT......................... 32
BATTERY TEMPERATURE SENSORÐ
PCM INPUT........................... 25
BATTERY VOLTAGEÐPCM INPUT........... 25
BRAKE SWITCHÐPCM INPUT.............. 25
CAMSHAFT POSITION SENSORÐPCM INPUT . 25
CHARGING SYSTEM INDICATOR LAMPÐ
PCM OUTPUT......................... 32
CRANKSHAFT POSITION SENSORÐ
PCM INPUT........................... 26
DATA LINK CONNECTOR.................. 33
DUTY CYCLE EVAP PURGE SOLENOIDÐ
PCM OUTPUT......................... 32
ELECTRIC EGR TRANSDUCERÐ
PCM OUTPUT......................... 32
ENGINE COOLANT TEMPERATURE SENSORÐ
PCM INPUT........................... 26
FUEL INJECTORSÐPCM OUTPUT.......... 34
FUEL LEVEL SENSORÐPCM INPUT......... 27
FUEL PUMP RELAYÐPCM OUTPUT......... 32
GENERATOR FIELDÐPCM OUTPUT......... 33
HEATED OXYGEN SENSOR (O2S SENSOR)Ð
PCM INPUT........................... 27
IDLE AIR CONTROL MOTORÐPCM OUTPUT . . 33
IGNITION CIRCUIT SENSEÐPCM INPUT..... 28
IGNITION COILÐPCM OUTPUT............. 34
INTAKE AIR TEMPERATURE SENSORÐ
PCM INPUT........................... 28
KNOCK SENSORÐPCM INPUT............. 29
MALFUNCTION INDICATOR (CHECK ENGINE)
LAMPÐPCM OUTPUT.................. 34
MANIFOLD ABSOLUTE PRESSURE (MAP)
SENSORÐPCM INPUT.................. 29
PARK/NEUTRAL POSITION SWITCHÐ
PCM INPUT........................... 30
POWER DISTRIBUTION CENTER........... 23
POWER STEERING PRESSURE SWITCHÐ
PCM INPUT........................... 30
POWERTRAIN CONTROL MODULE.......... 24SCI RECEIVEÐPCM INPUT................ 30
SCI RECEIVEÐPCM OUTPUT.............. 35
SENSOR RETURNÐPCM INPUT............ 30
SOLID STATE FAN RELAYÐPCM OUTPUT.... 35
SPEED CONTROL SERVOSÐPCM OUTPUT . . . 30
SPEED CONTROLÐPCM INPUT............ 35
SYSTEM DIAGNOSIS..................... 23
TACHOMETERÐPCM OUTPUT............. 35
THROTTLE POSITION SENSORÐPCM INPUT . 30
TORQUE CONVERTOR CLUTCH SOLENOIDÐ
PCM OUTPUT......................... 35
VEHICLE SPEED SENSORÐPCM INPUT..... 30
DIAGNOSIS AND TESTING
ASD AND FUEL PUMP RELAYS............. 46
CAMSHAFT AND CRANKSHAFT POSITION
SENSOR............................. 47
ENGINE COOLANT TEMPERATURE SENSOR . . 47
HEATED OXYGEN SENSOR............... 47
IDLE AIR CONTROL (IAC) MOTOR TEST...... 47
KNOCK SENSOR........................ 47
MANIFOLD ABSOLUTE PRESSURE (MAP)
SENSOR............................. 48
THROTTLE BODY MINIMUM AIR FLOW....... 48
THROTTLE POSITION SENSOR............ 48
VEHICLE SPEED SENSOR................ 49
VISUAL INSPECTIONÐDOHC.............. 40
VISUAL INSPECTIONÐSOHC.............. 35
REMOVAL AND INSTALLATION
AIR CLEANER ELEMENT.................. 55
CAMSHAFT POSITION SENSOR............ 54
CRANKSHAFT POSITION SENSOR.......... 54
DOWNSTREAM HEATED OXYGEN SENSOR . . . 55
DUTY CYCLE EVAP PURGE SOLENOID VALVE . 53
ENGINE COOLANT TEMPERATURE SENSOR . . 56
IDLE AIR CONTROL MOTOR............... 52
KNOCK SENSOR........................ 57
MAP/IAT SENSORÐDOHC................. 53
MAP/IAT SENSORÐSOHC................. 53
POWERTRAIN CONTROL MODULE (PCM).... 54
THROTTLE BODYÐAUTOMATIC
TRANSMISSION....................... 50
THROTTLE BODYÐMANUAL TRANSMISSION . 50
THROTTLE POSITION SENSOR (TPS)....... 52
UPSTREAM HEATED OXYGEN SENSOR...... 54
VEHICLE SPEED SENSOR................ 56
SPECIFICATIONS
TORQUE.............................. 57
VECI LABEL............................ 57
SPECIAL TOOLS
FUEL................................. 57
14 - 20 FUEL SYSTEMPL

GENERAL INFORMATION
INTRODUCTION
All engines used in this section have a sequential
Multi-Port Electronic Fuel Injection system. The MPI
system is computer regulated and provides precise
air/fuel ratios for all driving conditions. The Power-
train Control Module (PCM) operates the fuel injec-
tion system.
The PCM regulates:
²Ignition timing
²Air/fuel ratio
²Emission control devices
²Cooling fan
²Charging system
²Idle speed
²Vehicle speed control
Various sensors provide the inputs necessary for
the PCM to correctly operate these systems. In addi-
tion to the sensors, various switches also provide
inputs to the PCM.
All inputs to the PCM are converted into signals.
The PCM can adapt its programming to meet chang-
ing operating conditions.
Fuel is injected into the intake port above the
intake valve in precise metered amounts through
electrically operated injectors. The PCM fires the
injectors in a specific sequence. Under most operat-
ing conditions, the PCM maintains an air fuel ratio
of 14.7 parts air to 1 part fuel by constantly adjust-
ing injector pulse width. Injector pulse width is the
length of time the injector is open.
The PCM adjusts injector pulse width by opening
and closing the ground path to the injector. Engine
RPM (speed) and manifold absolute pressure (air
density) are the primary inputs that determine injec-
tor pulse width.
MODES OF OPERATION
As input signals to the PCM change, the PCM
adjusts its response to output devices. For example,
the PCM must calculate a different injector pulse
width and ignition timing for idle than it does for
Wide Open Throttle (WOT). There are several differ-
ent modes of operation that determine how the PCM
responds to the various input signals.
There are two different areas of operation, OPEN
LOOP and CLOSED LOOP.
During OPEN LOOP modes the PCM receives
input signals and responds according to preset PCM
programming. Inputs from the upstream and down-
stream heated oxygen sensors are not monitored dur-
ing OPEN LOOP modes, except for heated oxygen
sensor diagnostics (they are checked for shorted con-
ditions at all times).During CLOSED LOOP modes the PCM monitors
the inputs from the upstream and downstream
heated oxygen sensors. The upstream heated oxygen
sensor input tells the PCM if the calculated injector
pulse width resulted in the ideal air-fuel ratio of 14.7
to one. By monitoring the exhaust oxygen content
through the upstream heated oxygen sensor, the
PCM can fine tune injector pulse width. Fine tuning
injector pulse width allows the PCM to achieve opti-
mum fuel economy combined with low emissions.
For the PCM to enter CLOSED LOOP operation,
the following must occur:
(1) Engine coolant temperature must be over 35ÉF.
²If the coolant is over 35É the PCM will wait 44
seconds.
²If the coolant is over 50ÉF the PCM will wait 38
seconds.
²If the coolant is over 167ÉF the PCM will wait
11 seconds.
(2) For other temperatures the PCM will interpo-
late the correct waiting time.
(3) O2 sensor must read either greater than .745
volts or less than .1 volt.
(4) The multi-port fuel injection systems has the
following modes of operation:
²Ignition switch ON (Zero RPM)
²Engine start-up
²Engine warm-up
²Cruise
²Idle
²Acceleration
²Deceleration
²Wide Open Throttle
²Ignition switch OFF
(5) The engine start-up (crank), engine warm-up,
deceleration with fuel shutoff and wide open throttle
modes are OPEN LOOP modes. Under most operat-
ing conditions, the acceleration, deceleration (with
A/C on), idle and cruise modes,with the engine at
operating temperatureare CLOSED LOOP modes.
IGNITION SWITCH ON (ZERO RPM) MODE
When the ignition switch activates the fuel injec-
tion system, the following actions occur:
²The PCM monitors the engine coolant tempera-
ture sensor and throttle position sensor input. The
PCM determines basic fuel injector pulse width from
this input.
²The PCM determines atmospheric air pressure
from the MAP sensor input to modify injector pulse
width.
When the key is in the ON position and the engine
is not running (zero rpm), the Auto Shutdown (ASD)
and fuel pump relays de-energize after approximately
1 second. Therefore, battery voltage is not supplied to
the fuel pump, ignition coil, fuel injectors and heated
oxygen sensors.
PLFUEL SYSTEM 14 - 21