Input speed sensor JEEP GRAND CHEROKEE 2003 WJ / 2.G Owner's Guide

ENGINE CONTROL MODULE C1 (DIESEL) - BLACK 81 WAY
CAV CIRCUIT FUNCTION
1 Z108 14BK/DG GROUND
2 Z108 14BK/DG GROUND
3 K20 14DB GENERATOR FIELD CONTROL
4 F142 14RD/DG FUSED AUTO SHUT DOWN RELAY OUTPUT
5 F142 14RD/DG FUSED AUTO SHUT DOWN RELAY OUTPUT
6 D52 18DG/WT CAN C BUS(+)
7 D25 20VT/YL PCI BUS
8 K944 20BR/DG CAMSHAFT POSITION SENSOR GROUND
9 K44 20YL/GY CAMSHAFT POSITION SENSOR SIGNAL
10 - -
11 Y53 20BK/YL BOOST PRESSURE SENSOR SIGNAL
12 K155 20YL/WT MASS AIR FLOW SENSOR SIGNAL
13 Y40 20DG/VT FUEL PRESSURE SENSOR SIGNAL
14 K22 20RD/DB ACCELERATOR PEDAL POSITION SENSOR 2 SIGNAL
15 K81 20DB/DG ACCELERATOR PEDAL POSITION SENSOR 1 SIGNAL
16 Y100 20BR/GY FUEL PRESSURE SENSOR GROUND
17 - -
18 - -
19 F300 20RD/BK BATTERY SENSE (+)
20 Z11 20BK/WT BATTERY SENSE (-)
21 K4 18BK/LB SENSOR GROUND
22 F991 20RD/DB FUSED IGNITION SWITCH OUTPUT (RUN-START)
23 K6 18VT/WT SENSOR REFERENCE VOLTAGE B
24 K3 20BK CRANKSHAFT POSITION SENSOR SIGNAL 1
25 D51 18WT CAN C BUS(-)
26 - -
27 - -
28 - -
29 K77 20BR/WT TRANSFER CASE POSITION SENSOR INPUT
30 G60 20BR/DB ENGINE OIL PRESSURE SENSOR SIGNAL
31 - -
32 K25 20VT/DG BATTERY TEMPERATURE SENSOR SIGNAL
33 - -
34 K255 20WT/DG ACCELERATOR PEDAL POSITION SENSOR 1 GROUND
35 Y43 20WT/VT ACCELERATOR PEDAL POSITION SENSOR 1 5-VOLT
SUPPLY
36 C18 20DB A/C PRESSURE SENSOR SIGNAL
37 - -
38 V37 20RD/DG SPEED CONTROL SWITCH SIGNAL
39 K226 20DB/WT FUEL LEVEL SENSOR SIGNAL
40 K2 20DG/RD ENGINE COOLANT TEMPERATURE SENSOR SIGNAL
41 K21 20DG/WT INTAKE AIR TEMPERATURE SENSOR SIGNAL
42 Y101 20 CRANKSHAFT POSITION SENSOR SHIELD
43 K924 20YL CRANKSHAFT POSITION SENSOR SIGNAL 2
44 - -
45 - -
46 - -
47 L50 20WT/DB PRIMARY BRAKE SWITCH SIGNAL
48 K29 20WT/PK SECONDARY BRAKE SWITCH SIGNAL
49 - -
50 F855 18BR/YL SENSOR REFERENCE VOLTAGE A
51 - -
52 - -
53 - -
54 Z189 20BR MASS AIR FLOW SENSOR GROUND
WJ8W-80 CONNECTOR PIN-OUT 8W - 80 - 75

INPUT SPEED SENSOR (4.7L) - BLACK 2 WAY
CAV CIRCUIT FUNCTION
1 T52 18RD/BK INPUT SPEED SENSOR SIGNAL
2 T13 18DB/BK SPEED SENSOR GROUND
INSTRUMENT CLUSTER - WHITE 12 WAY
CAV CIRCUIT FUNCTION
1 L61 20TN/LG LEFT TURN SIGNAL
2 L60 20TN RIGHT TURN SIGNAL
3- -
4- -
5 G9 20GY/BK RED BRAKE WARNING INDICATOR DRIVER
6 F33 20PK/RD FUSED B(+)
7 G5 20DB/WT FUSED IGNITION SWITCH OUTPUT (RUN-START)
8 D19 20VT/OR BODY CONTROL MODULE FLASH ENABLE
9 Z300 20BK GROUND
10 D25 20YL/VT/RD PCI BUS
11 Z132 20BK/OR GROUND
12 - -
INTAKE AIR TEMPERATURE SENSOR (DIESEL) - BLACK 2 WAY
CAV CIRCUIT FUNCTION
1 K4 20BK/LB SENSOR GROUND
2 K21 20DG/WT INTAKE AIR TEMPERATURE SENSOR SIGNAL
INTAKE AIR TEMPERATURE SENSOR (GAS) - GRAY 2 WAY
CAV CIRCUIT FUNCTION
1 K4 18BK/LB SENSOR GROUND
2 K21 18BK/RD INTAKE AIR TEMPERATURE SENSOR SIGNAL
WJ8W-80 CONNECTOR PIN-OUT 8W - 80 - 85

TRANSMISSION CONTROL MODULE (4.7L) - BLACK 60 WAY
CAV CIRCUIT FUNCTION
1 T1 18LG/BK TRS T1 SENSE
2 T2 18TN/BK TRS T2 SENSE
3 T3 18VT TRS T3 SENSE
4- -
5- -
6 K24 18GY/BK CRANKSHAFT POSITION SENSOR SIGNAL
7 D21 18PK SCI TRANSMIT
8 F45 18YL/RD FUSED IGNITION SWITCH OUTPUT (START)
9 T9 18OR/BK OVERDRIVE PRESSURE SWITCH SENSE
10 T10 18YL/DG TORQUE MANAGEMENT REQUEST SENSE
11 F991 18OR/DB FUSED IGNITION SWITCH OUTPUT (RUN-START)
12 K22 18OR/RD THROTTLE POSITION SENSOR SIGNAL
13 T13 18DB/BK SPEED SENSOR GROUND
14 T14 18LG/WT OUTPUT SPEED SENSOR SIGNAL
15 K30 18PK/YL TRANSMISSION CONTROL RELAY CONTROL
16 T16 14RD TRANSMISSION CONTROL RELAY OUTPUT
17 T16 14RD TRANSMISSION CONTROL RELAY OUTPUT
18 T118 18YL/DB PRESSURE CONTROL SOLENOID CONTROL
19 T119 18WT/DB 2C SOLENOID CONTROL
20 T120 18LG LR SOLENOID CONTROL
21 - -
22 - -
23 - -
24 - -
25 - -
26 - -
27 - -
28 - -
29 T29 18GY UNDERDRIVE PRESSURE SWITCH SENSE
30 T130 14VT/TN LINE PRESSURE SENSOR SIGNAL
31 - -
32 - -
33 - -
34 - -
35 - -
36 T16 14RD TRANSMISSION CONTROL RELAY OUTPUT
37 Z113 14BK/WT GROUND
38 T138 14GY/LB 5 VOLT SUPPLY
39 Z112 14BK/YL GROUND
40 T140 18VT/LG MS SOLENOID CONTROL
41 T41 18WT TRS T41 SENSE
42 T42 18VT/WT TRS T42 SENSE
43 D25 18YL/VT PCI BUS
44 - -
45 - -
46 D20 18LG SCI RECEIVE
47 T147 18LB 2C PRESSURE SWITCH SENSE
48 T48 18DB 4C PRESSURE SWITCH SENSE
49 T6 18VT/WT OVERDRIVE OFF SWITCH SENSE
50 T150 18BR/LB LR PRESSURE SWITCH SENSE
51 K4 18BK/LB SENSOR GROUND
52 T52 18RD/BK INPUT SPEED SENSOR SIGNAL
53 Z114 14BK/LG GROUND
54 T54 18VT TRANSMISSION TEMPERATURE SENSOR SIGNAL
55 T59 18PK UNDERDRIVE SOLENOID CONTROL
56 A30 14RD/WT FUSED B(+)
57 Z12 14BK/TN GROUND
58 - -
59 T159 18DG/WT 4C SOLENOID CONTROL
60 T60 18BR OVERDRIVE SOLENOID CONTROL
8W - 80 - 124 8W-80 CONNECTOR PIN-OUTWJ

TRANSMISSION CONTROL MODULE C1 (DIESEL) - BLACK 18 WAY
CAV CIRCUIT FUNCTION
1 D21 20PK SCI TRANSMIT
2- -
3 W4 20PK/OR SHIFTER C5 SENSE
4 Y1 20DB/PK PARK LOCKOUT SOLENOID CONTROL
5- -
6- -
7 T41 20BK/WT PARK/NEUTRAL POSITION SWITCH SENSE (T41)
8- -
9- -
10 - -
23 - -
24 - -
25 W0 20DB/WT SHIFTER C1 SENSE
26 W1 20VT/WT SHIFTER C2 SENSE
27 W2 20VT SHIFTER C3 SENSE
28 W3 20BK SHIFTER C4 SENSE
29 F991 20OR/DB FUSED IGNITION SWITCH OUTPUT (RUN-START)
30 Z234 20WT GROUND
TRANSMISSION CONTROL MODULE C2 (DIESEL) - BLACK 14 WAY
CAV CIRCUIT FUNCTION
12 T52 18RD/BK N2 INPUT SPEED SENSOR
13 T39 18GY/LB SENSOR SUPPLY VOLTAGE
14 T60 18BR 1-2/4-5 SOLENOID CONTROL
15 T159 18DG/WT 3-4 SOLENOID CONTROL
16 T119 18WT/DB 2-3 SOLENOID CONTROL
17 T120 18LG TCC SOLENOID CONTROL
33 T13 18DB/BK SENSOR GROUND
34 T54 18VT TEMP SENSOR - P/N SWITCH
35 T14 18LG/WT N3 INPUT SPEED SENSOR
36 T591 18YL/DB MODULATION PRESSURE SOLENOID CONTROL
37 T118 18YL/DB SHIFT PRESSURE SOLENOID CONTROL
38 T16 18RD SOLENOID SUPPLY VOLTAGE
H1 D52 18LG/WT CAN C BUS(+)
L2 D51 18DG/WT CAN C BUS(-)
TRANSMISSION SOLENOID (4.0L) - BLACK 8 WAY
CAV CIRCUIT FUNCTION
1 T15 18LG FUSED TRANSMISSION CONTROL RELAY OUTPUT
2 K6 18VT/BK 5 VOLT SUPPLY
3 K4 18BK/LB SENSOR GROUND
4 T25 18LG/RD GOVERNOR PRESSURE SENSOR SIGNAL
5 K88 18PK GOVERNOR PRESSURE SOLENOID CONTROL
6 T60 18BR 3-4 SHIFT SOLENOID CONTROL
7 T20 18LB TORQUE CONVERTER CLUTCH SOLENOID CONTROL
8 T54 18VT TRANSMISSION TEMPERATURE SENSOR SIGNAL
WJ8W-80 CONNECTOR PIN-OUT 8W - 80 - 125

TRANSMISSION SOLENOID ASSEMBLY (DIESEL) - BLACK 13 WAY
CAV CIRCUIT FUNCTION
1 T14 18LG/WT N3 INPUT SPED SENSOR
2 T591 18YL/DB MODULATION PRESSURE SOLENOID CONTROL
3 T52 18RD/BK N2 INPUT SPEED SENSOR
4 T54 18VT TEMP SENSOR - P/N SWITCH
5- -
6 T16 18RD SOLENOID SUPPLY VOLTAGE
7 T39 18GY/LB SENSOR SUPPLY VOLTAGE
8 T119 18WT/DB 2-3 SOLENOID CONTROL
9 T159 18DG/WT 3-4 SOLENOID CONTROL
10 T118 18YL/DB SHIFT PRESSURE SOLENOID CONTROL
11 T120 18LG TCC SOLENOID CONTROL
12 T13 18DB/BK SENSOR GROUND
13 T60 18BR 1-2/4-5 SOLENOID CONTROL
TRANSMISSION SOLENOID/TRS ASSEMBLY (4.7L) - GRAY 23 WAY
CAV CIRCUIT FUNCTION
1 F22 18WT/PK FUSED IGNITION SWITCH OUTPUT (RUN)
2 T120 18LG LR SOLENOID CONTROL
3 T41 18BK/WT PARK/NEUTRAL POSITION SWITCH SENSE (T41)
4 T141 18WT TRS T41 SENSE
5 T42 18VT/WT TRS T42 SENSE
6 L1 18VT/BK BACK-UP LAMP FEED
7 T60 18BR OVERDRIVE SOLENOID CONTROL
8 T3 18VT TRS T3 SENSE
9 T1 18LG/BK TRS T1 SENSE
10 T16 14RD TRANSMISSION CONTROL RELAY OUTPUT
11 T48 18DB 4C PRESSURE SWITCH SENSE
12 T118 18YL/DB PRESSURE CONTROL SOLENOID CONTROL
13 T2 18TN/BK TRS T2 SENSE
14 T150 18BR/LB LR PRESSURE SWITCH SENSE
15 T147 18LB 2C PRESSURE SWITCH SENSE
16 T9 18OR/BK OVERDRIVE PRESSURE SWITCH SENSE
17 T59 18PK UNDERDRIVE SOLENOID CONTROL
18 T29 18GY UNDERDRIVE PRESSURE SWITCH SENSE
19 T159 18DG/WT 4C SOLENOID CONTROL
20 T119 18WT/DB 2C SOLENOID CONTROL
21 T140 18VT/LG MS SOLENOID CONTROL
22 T13 18DB/BK SPEED SENSOR GROUND
23 T54 18VT TRANSMISSION TEMPERATURE SENSOR SIGNAL
UNDERHOOD LAMP - BLACK 2 WAY
CAV CIRCUIT FUNCTION
1 Z141 20BK GROUND
2 M1 20PK/RD FUSED B(+)
8W - 80 - 126 8W-80 CONNECTOR PIN-OUTWJ

CONNECTOR NAME/
NUMBERCOLOR LOCATION FIG.
Fuel Pump Module (Gas) BK Near Fuel Tank 33, 35
Fuel Tank Module Diesel) BK Near Fuel Tank 33, 35
Generator (Diesel) LTGY At Generator 8
Generator (Gas) BK At Generator N/S
Glove Box Lamp BK Inside Glove Box 19, 20, 22
Headlamp Leveling Switch
(Built-Up-Export)WT Driver Side of Instrument Panel 20
Hood Ajar Switch BK Left Side of Engine Compartment 3, 4
Horn No.1 BK Right Front Fascia 5
Horn No.2 BK Right Front Fascia 5
Hydraulic Cooling Module BK Right Front of Engine Compartment 5
Idle Air Control Motor BK Left Side of Engine Near Throttle
Body13
Ignition Switch - C1 WT On Steering Column 23
Ignition Switch - C2 BK On Steering Column 23
Input Speed Sensor (4.7L) BK Left Side of Transmission 16
Instrument Cluster WT At Instrument Cluster 19, 20
Intake Air Temperature Sensor
(Gas)GY Left Side of Engine 9, 13
Intake Air Temperature Sensor
(Diesel)BK Near T/O for Crankcase Heater 8
Intake Port Swirl Actuator
(Diesel)BK Right Rear of Engine Compartment N/S
Intrusion Transceiver Module
(Built-up-Export)BK In The Overhead N/S
Junction Block - C1 BK At Junction Block 30, 31, 33
Junction Block - C2 BK At Junction Block 30, 31
Junction Block - C3 BK At Junction Block 21, 22, 30
Junction Block - C4 WT At Junction Block 30, 31
Junction Block - C5 WT At Junction Block 30, 31
Knock Sensor (4.7L High
Output)BK Right Rear Side of Engine, Near
Coil on Plug No.8N/S
Leak Detection Pump (Except
Built-Up-Export)Left Front Wheel Opening 3
Left Courtesy Lamp BK Left Side of Instrument Panel 21 22, 23
Left Curtain Airbag BK Near Left C Pillar 37
Left Door Handle Courtesy
LampBK At Lamp N/S
Left Fog Lamp BK At Lamp 3, 4
Left Front Door Speaker WT In Left Front Door 24, 27
Left Front Impact Sensor BK Left Front Frame Near Windshield
Washer Pump3, 4
Left Front Park Lamp WT At Lamp N/S
8W - 91 - 6 8W-91 CONNECTOR/GROUND/SPLICE LOCATIONWJ
CONNECTOR/GROUND/SPLICE LOCATION (Continued)

SPLICE
NUMBERLOCATION FIG.
S122 (4.0L) Near T/O for G103 10, 11
S122 (4.7L) LHD Near T/O for Input Speed Sensor 15
S122 (4.7L) RHD Near T/O for Powertrain Control Module 16
S122 (Diesel) Near T/O for Generator N/S
S123 (4.0L) Near T/O for Capacitor 10, 11
S124 (4.7L) In Trough Near T/O for Capacitor No.2 13
S125 (Diesel) In T/O for C103 and C105 Left Rear of Engine Compartment N/S
S125 (Gas) Near T/O for Powertrain Control Module - C3 N/S
S126 (4.0L) LHD Near T/O for Battery Temperature Sensor N/S
S126 (4.0L) RHD In Trough Near T/O for Powertrain Control Module - C3 N/S
S127 (LHD) Gas In Trough Near T/O for Powertrain Control Module - C3 N/S
S127 (RHD) Gas In T/O for Power Distribution Center 5
S127 (Diesel) Near T/O for Power Distribution Center 4
S128 (Diesel) In T/O for C102 Left Rear of Engine Compartment N/S
S128 (LHD) Gas In Trough Near T/O for Powertrain Control Module - C3 N/S
S128 (RHD) Gas In T/O for C102 5
S130 (LHD) Gas In T/O for C102 N/S
S130 (RHD) Gas In T/O for Controller Antilock Brake 3
S130 (Diesel) In T/O for Controller Anti-Lock Brake 4
S131 In Trough Near T/O for Power Distribution Center 5
S131 (Diesel) Near T/O for Power Distribution Center 4
S132 (Diesel) Near T/O for EGR Solenoid N/S
S132 (Gas) Near T/O for Battery Temperature Sensor 5
S133 (Diesel) In Trough Near T/O for EGR Solenoid N/S
S133 (Gas) Near T/O for Battery Temperature Sensor 5
S134 (Diesel) In Trough Near T/O for G106/G107 4
S134 (Gas) In Trough Near T/O for Controller Anti-Lock Brake 3
S135 (Diesel) Near T/O for Engine Control Module C1 7, 8
S136 (Diesel) Near T/O for Engine Control Module C1 7, 8
S137 (Diesel) In Trough Near T/O for Coolant Level Sensor N/S
S139 (Diesel) Near T/O for Engine Control Module C1 7, 8
S140 (Diesel) Near T/O for Power Distribution Center 4
S140 (Gas) Near T/O for Controller Antilock Brake N/S
S141 (Gas) Near T/O for Controller Antilock Brake 3
S142 (Diesel) In Trough Near T/O for Coolant Level Sensor N/S
S142 Gas In T/O for C102 5
S143 (Diesel) In Trough Near T/O for Hood Ajar Switch 4
S143 (Gas,
Built-Up-Export)
LHDIn Trough Near T/O for Controller Antilock Brake 3
S143 Gas RHD Near T/O for Evap/Purge Solenoid N/S
S145 (Diesel) Near T/O for Engine Control Module C1 7, 8
WJ8W-91 CONNECTOR/GROUND/SPLICE LOCATION 8W - 91 - 13
CONNECTOR/GROUND/SPLICE LOCATION (Continued)

CRANKSHAFT POSITION
SENSOR
DESCRIPTION
DESCRIPTION - 4.0L
The Crankshaft Position Sensor (CKP) is mounted
to the transmission bellhousing at the left/rear side
of the engine block (Fig. 17).
DESCRIPTION - 4.7L
The Crankshaft Position Sensor (CKP) is mounted
into the engine block above the starter motor (Fig.
18).
OPERATION
OPERATION - 4.0L
Engine speed and crankshaft position are provided
through the crankshaft position sensor. The sensor
generates pulses that are the input sent to the pow-
ertrain control module (PCM). The PCM interprets
the sensor input to determine the crankshaft posi-
tion. The PCM then uses this position, along withother inputs, to determine injector sequence and igni-
tion timing.
Fig. 16 Accelerator Pedal Mounting
1 - CLIP
2 - ACCELERATOR CABLE
3 - CABLE CONNECTOR
4 - MOUNTING NUTS (2)
5 - PEDAL/BRACKET ASSEMBLY
6 - MOUNTING STUDS (2)
Fig. 17 CKP Sensor LocationÐ4.0L 6-Cyl. Engine
1 - SLOTTED HOLE
2 - CRANKSHAFT POSITION SENSOR
3 - WIRE SHIELD
4 - MOUNTING BOLT
5 - TRANSMISSION HOUSING
6 - PAPER SPACER
Fig. 18 CKP Sensor LocationÐ4.7L V±8 Engine
1 - CRANKSHAFT POSITION SENSOR
2-STARTER
3 - ELEC. CONNECTOR
14 - 40 FUEL INJECTIONWJ
ACCELERATOR PEDAL (Continued)

The sensor is a hall effect device combined with an
internal magnet. It is also sensitive to steel within a
certain distance from it.
On 4.0L 6-cylinder engines, the flywheel/drive
plate has 3 sets of four notches at its outer edge (Fig.
19).
The notches cause a pulse to be generated when
they pass under the sensor. The pulses are the input
to the PCM. For each engine revolution there are 3
sets of four pulses generated.
The trailing edge of the fourth notch, which causes
the pulse, is four degrees before top dead center
(TDC) of the corresponding piston.
The engine will not operate if the PCM does not
receive a crankshaft position sensor input.
OPERATION - 4.7L
Engine speed and crankshaft position are provided
through the crankshaft position sensor. The sensor
generates pulses that are the input sent to the pow-
ertrain control module (PCM). The PCM interprets
the sensor input to determine the crankshaft posi-
tion. The PCM then uses this position, along with
other inputs, to determine injector sequence and igni-
tion timing.
The sensor is a hall effect device combined with an
internal magnet. It is also sensitive to steel within a
certain distance from it.On the 4.7L V±8 engine, a tonewheel is bolted to
the engine crankshaft (Fig. 20). This tonewheel has
sets of notches at its outer edge (Fig. 20).
The notches cause a pulse to be generated when
they pass under the sensor. The pulses are the input
to the PCM.
REMOVAL
REMOVAL - 4.0L
The Crankshaft Position (CKP) sensor is mounted
to the transmission bellhousing at the left/rear side
of the engine block (Fig. 21). The sensoris adjust-
ableand is attached with one bolt. A wire shield/
router is attached to the sensor (Fig. 21).
(1) Disconnect sensor pigtail harness (3±way con-
nector) from main engine wiring harness.
(2) Remove sensor mounting bolt.
(3) Remove wire shield and sensor.
REMOVAL - 4.7L
The Crankshaft Position (CKP) sensor is bolted to
the side of the engine cylinder block above the
starter motor (Fig. 22). It is positioned into a
machined hole at the side of the engine block.
(1) Remove starter motor. Refer to Starter Remov-
al/Installation.
Fig. 19 CKP Sensor OperationÐ4.0L 6-Cyl. Engine
1 - CRANKSHAFT POSITION SENSOR
2 - FLYWHEEL
3 - FLYWHEEL NOTCHES
Fig. 20 CKP Sensor Operation and TonewheelÐ4.7L
V±8 Engine
1 - TONEWHEEL
2 - NOTCHES
3 - CRANKSHAFT POSITION SENSOR
4 - CRANKSHAFT
WJFUEL INJECTION 14 - 41
CRANKSHAFT POSITION SENSOR (Continued)

MAP SENSOR
DESCRIPTION
DESCRIPTION
On the 4.0L six-cylinder engine the MAP sensor is
mounted to the engine throttle body. On the 4.7L V-8
engine the MAP sensor is mounted to front of the
intake manifold.
DESCRIPTION - 4.7L
The MAP sensor is located on the front of the
intake manifold. An o-ring seals the sensor to the
intake manifold.
OPERATION
The MAP sensor is used as an input to the Power-
train Control Module (PCM). It contains a silicon
based sensing unit to provide data on the manifold
vacuum that draws the air/fuel mixture into the com-
bustion chamber. The PCM requires this information
to determine injector pulse width and spark advance.
When manifold absolute pressure (MAP) equals
Barometric pressure, the pulse width will be at max-
imum.
A 5 volt reference is supplied from the PCM and
returns a voltage signal to the PCM that reflects
manifold pressure. The zero pressure reading is 0.5V
and full scale is 4.5V. For a pressure swing of 0±15
psi, the voltage changes 4.0V. To operate the sensor,
it is supplied a regulated 4.8 to 5.1 volts. Ground is
provided through the low-noise, sensor return circuit
at the PCM.
The MAP sensor input is the number one contrib-
utor to fuel injector pulse width. The most important
function of the MAP sensor is to determine baromet-
ric pressure. The PCM needs to know if the vehicle is
at sea level or at a higher altitude, because the air
density changes with altitude. It will also help to cor-
rect for varying barometric pressure. Barometric
pressure and altitude have a direct inverse correla-
tion; as altitude goes up, barometric goes down. At
key-on, the PCM powers up and looks at MAP volt-
age, and based upon the voltage it sees, it knows the
current barometric pressure (relative to altitude).
Once the engine starts, the PCM looks at the voltage
again, continuously every 12 milliseconds, and com-
pares the current voltage to what it was at key-on.
The difference between current voltage and what it
was at key-on, is manifold vacuum.
During key-on (engine not running) the sensor
reads (updates) barometric pressure. A normal range
can be obtained by monitoring a known good sensor.
As the altitude increases, the air becomes thinner
(less oxygen). If a vehicle is started and driven to avery different altitude than where it was at key-on,
the barometric pressure needs to be updated. Any
time the PCM sees Wide Open Throttle (WOT), based
upon Throttle Position Sensor (TPS) angle and RPM,
it will update barometric pressure in the MAP mem-
ory cell. With periodic updates, the PCM can make
its calculations more effectively.
The PCM uses the MAP sensor input to aid in cal-
culating the following:
²Manifold pressure
²Barometric pressure
²Engine load
²Injector pulse-width
²Spark-advance programs
²Shift-point strategies (certain automatic trans-
missions only)
²Idle speed
²Decel fuel shutoff
The MAP sensor signal is provided from a single
piezoresistive element located in the center of a dia-
phragm. The element and diaphragm are both made
of silicone. As manifold pressure changes, the dia-
phragm moves causing the element to deflect, which
stresses the silicone. When silicone is exposed to
stress, its resistance changes. As manifold vacuum
increases, the MAP sensor input voltage decreases
proportionally. The sensor also contains electronics
that condition the signal and provide temperature
compensation.
The PCM recognizes a decrease in manifold pres-
sure by monitoring a decrease in voltage from the
reading stored in the barometric pressure memory
cell. The MAP sensor is a linear sensor; meaning as
pressure changes, voltage changes proportionately.
The range of voltage output from the sensor is usu-
ally between 4.6 volts at sea level to as low as 0.3
volts at 26 in. of Hg. Barometric pressure is the pres-
sure exerted by the atmosphere upon an object. At
sea level on a standard day, no storm, barometric
pressure is approximately 29.92 in Hg. For every 100
feet of altitude, barometric pressure drops .10 in. Hg.
If a storm goes through it can change barometric
pressure from what should be present for that alti-
tude. You should know what the average pressure
and corresponding barometric pressure is for your
area.
REMOVAL
REMOVAL - 4.0L
The MAP sensor is mounted to the side of the
throttle body (Fig. 40). An L-shaped rubber fitting is
used to connect the MAP sensor to throttle body (Fig.
31).
(1) Remove air cleaner duct and air resonator box
at throttle body.
14 - 48 FUEL INJECTIONWJ