Jeep Cherokee 1988 User manual

FUEL INJECTION SYSTEM - MULTI-POINT
1988 Jeep Cherokee
1988 Electronic Fuel Injection
JEEP MULTI-POINT
4.0L Cherokee, Comanche, Wagoneer
DESCRIPTION
The Multi-Point Electronic Fuel Injection (EFI) system is an
electronically controlled system which combines electronic sequential
fuel injection and electronic spark advance systems. Main sub-systems
consist of: air induction, fuel delivery, fuel control, emission
control, Electronic Control Unit (ECU), data sensors and switches.
Air induction system includes air cleaner, throttle body,
Throttle Position Sensor (TPS) and the Idle Speed Stepper (ISS) motor.
Fuel delivery system provides fuel from fuel pump to the
fuel control system. Fuel system is composed of an in-tank electric
fuel pump, fuel filter and return line. Power is provided to operate
fuel pump through a fuel pump relay located on right inner fender
panel.
Fuel control system handles actual fuel delivery into the
engine. Fuel pressure regulator maintains a constant fuel pressure of
31-39 psi (2.1-2.7 kg/cm

). In addition to the regulator, fuel
system consists of the fuel rail and 4 fuel injectors. On MPI engine,
ECU controls EGR/EVAP solenoid operation.
The ECU is a digital microprocessor computer. ECU receives
input signals from various switches and sensors. ECU then computes
fuel injector pulse width ("on" time), spark advance, ignition module
dwell, idle speed, canister purge cycles, EGR flow and feedback
control from this information.
OPERATION
AIR INDUCTION
Air is drawn into combustion chamber through air cleaner and
intake manifold. Amount of air entering engine is controlled by
position of throttle body valve. Throttle body houses throttle
position sensor (TPS) and idle speed solenoid (ISS) motor. TPS is an
electrical resistor which is connected to throttle valve. TPS
transmits a signal to ECU in relation to throttle valve angle. This
signal is used in calculations to determine injector pulse width to
provide adequate air/fuel mixture.
ECU controls idle speed by providing appropriate voltage
outputs to move ISS motor pin inward or outward to maintain a
predetermined idle speed. ECU continuously monitors TPS and ISS motor
and issues change commands to injectors to increase or decrease
amount of fuel injected.
FUEL DELIVERY
Power to fuel pump relay is supplied from ignition switch
when in "ON" or "START" position, at which time the ECU supplies a
ground for fuel pump relay. When relay contacts are closed, power is
applied to fuel pump.
Fuel is drawn through one end of a roller-type electric fuel
pump, compressed and forced out opposite end. Pump capacity is
greater than maximum engine consumption so that pressure in fuel
system is always maintained.

FUEL CONTROL
Fuel control system handles actual delivery of fuel to
engine. See Fig. 1. Fuel from fuel pump enters fuel rail, injectors
and pressure regulator. Based upon a manifold vacuum signal, pressure
regulator maintains a constant fuel pressure in fuel system of
approximately 31-39 psi (2.1-2.7 kg/cm

) by allowing excess fuel to
return to fuel tank.
Fuel injectors are electrically operated solenoid valves
which are energized by the ECU. The ECU determines injector pulse
width ("on" time) based upon input from the various sensors.
Fig. 1: Fuel Control Components
Courtesy of Chrysler Motors.
EMISSION CONTROL
ECU controls EGR valve and fuel evaporative operation. By
energizing the EGR/EVAP solenoid, vacuum is shut off, making this
system non-operative. When engine reaches normal operating
temperatures, ECU de-energizes solenoid. When de-energized, solenoid
allows vacuum to flow to EGR valve. ECU will energize solenoid
whenever EGR action is undesirable, during idle, cold engine
operation, wide open throttle and rapid acceleration or deceleration.
ELECTRONIC CONTROL UNIT (ECU)

ECU is a digital microprocessor computer. Data sensors
provide the ECU with engine operating information in varying
electrical signals. ECU calculates this information and corrects
air/fuel ratio, ignition timing, and emission control as needed to
maintain efficient engine operation. Other ECU output signals control
upshift indicator light (manual transmission only), ignition module
dwell and A/C clutch operation.
UPSHIFT INDICATOR
On vehicles equipped with a manual transmission, ECU
controls upshift indicator light. Indicator light is normally
illuminated when ignition is turned on without engine running.
Indicator light is turned off when engine is started.
Indicator light will be illuminated during engine operation
in response to engine load and speed. If transmission is not shifted,
ECU will turn light off after 3 to 5 seconds. A switch located on
transmission prevents indicator light from being illuminated when
transmission is shifted to highest gear.
DATA SENSORS & SWITCHES
Manifold Absolute Pressure (MAP) Sensor
MAP sensor is located in engine compartment on firewall,
behind engine. MAP sensor monitors manifold vacuum via a vacuum line
from intake manifold to sensor.
MAP sensor supplies an electrical signal which keeps ECU
informed of manifold vacuum and barometric pressure conditions. This
information is combined with data supplied by other sensors to
determine correct air/fuel ratio.
Oxygen Sensor
Oxygen (O2) sensor is mounted in exhaust manifold where it
is exposed to exhaust gas flow. Its function is to monitor oxygen
content of exhaust gases and to supply ECU with a voltage signal
directly proportional to this content.
If oxygen content of exhaust gases is high (lean air/fuel
mixture), voltage signal to ECU is low. As oxygen content decreases
(mixture becomes richer), signal voltage increases.
In this way, ECU is kept constantly informed of air/fuel
ratio. ECU can then alter fuel injector "on" time, in response to
these signals, to obtain best air/fuel ratio of 14.7:1 under any
given operating conditions.
O2 sensor is equipped with a heating element that keeps
sensor at proper operating temperatures. Maintaining correct sensor
temperatures at all times guarantees a more accurate signal to ECU.
By using an O2 heater, fuel control system may also enter "closed
loop" operating mode sooner and maintain this mode, even during
periods of extended idle.
Temperature Sensors
There are 2 temperature sensors used on this system.
Manifold Air Temperature (MAT) sensor, mounted in intake manifold,
measures temperature of incoming air/fuel mixture and Coolant
Temperature Sensor (CTS), located on left side of cylinder block just
below the exhaust manifold, measures temperature of engine coolant.
Information provided by these 2 sensors to ECU allows ECU to
demand slightly richer air/fuel mixtures and higher idle speeds
during cold engine operation.
Throttle Position Sensor (TPS)
TPS is regulated by movement of throttle shaft. It is

mounted on throttle body and senses angle of throttle blade opening.
A voltage signal of up to 5 volts at wide open throttle is
produced by TPS. Voltage varies with throttle angle changes. This
signal is transmitted to ECU where it is used to adjust air/fuel
ratio during acceleration, deceleration, idle, and wide open throttle
conditions.
A dual TPS is used on models with automatic transmissions.
This dual TPS not only provides ECU with input voltages but also
supplies automatic transmission control unit with input signals
relative to throttle position.
Knock Sensor
Knock sensor (detonation sensor) is located on lower left
side of cylinder block just above oil pan. Knock sensor picks up
detonation vibration from engine and converts it to an electrical
signal for use by ECU.
ECU uses this information to determine when a change in
ignition timing is required. Knock sensor allows for engine operation
on either "premium" unleaded or "regular" unleaded fuel.
When knock occurs, ECU retards ignition timing in one or
more cylinders until detonation is eliminated.
Speed Sensor
Speed sensor is secured by special shouldered bolts to
flywheel/drive plate housing. Speed sensor is nonadjustable and
preset at factory. Speed sensor senses TDC and engine speed by
detecting flywheel teeth as they pass pick-up coil during engine
operation. See Fig. 2.
Flywheel has a large trigger tooth and notch located 12
small teeth before each TDC position. When a small tooth and notch
pass the magnetic core in sensor, concentration and collapse of the
magnetic field created induces a small voltage spike into sensor
pick-up coil windings. These small voltage spikes are sent to ECU,
allowing ECU to count the teeth as they pass sensor.
When a large tooth and notch pass magnetic core in sensor,
increased concentration and collapse of the magnetic field induces a
higher voltage spike than smaller teeth. Higher spike indicates to
ECU that a piston will soon be at TDC position, 12 teeth later.
Ignition timing for cylinder is either advanced or retarded by ECU
based upon "sensor input".
Fig. 2: Speed Sensor Operation
Courtesy of Chrysler Motors.
Engine Switches
Several switches provide operating information to ECU. These

include Park/Neutral switch (automatic transmission only), air
conditioning clutch, and Sync Pulse switch. When A/C or Park/Neutral
switches supply ECU with an "on" signal, module signals ISS motor to
change idle speed to a specific RPM.
With A/C on and throttle blade above a specific angle, ECU
de-energizes A/C relay, preventing A/C clutch from engaging until
throttle blade angle is reduced.
Sync pulse switch, located within distributor, generates a
signal to ECU, helping to properly synchronize sequential fuel
injection opening with intake valve opening.
ADJUSTMENTS
NOTE: Idle speed and air/fuel mixture are controlled by ECU and
are non-adjustable. On-car adjustment procedures for other
components should not be necessary during normal vehicle
operation or maintenance. Adjustments of components should
only be required when a faulty component is replaced with a
new one.
THROTTLE POSITION SENSOR (TPS)
1) Turn ignition on. Check throttle position sensor input
voltage. Connect voltmeter negative lead to terminal "B" (M/T), or
terminal "D" (A/T) of sensor connector. Connect voltmeter positive
lead to terminal "A" (M/T and A/T) of sensor connector.
NOTE: On (A/T) models, connector terminals are identified by
letters molded into back of connector. On all models, do not
disconnect TPS harness connector. Insert voltmeter test
leads through back of wire harness connector. On some
models, it may be necessary to remove throttle body from
intake manifold to gain access to sensor wire harness.
2) Move and close throttle plate completely (M/T and A/T).
Ensure throttle linkage contacts stop. Note voltmeter reading. Input
voltage at terminals "B" and "A" (M/T), or terminals "A" and "D"
(A/T) should be 5 volts.
3) Return throttle plate to closed throttle position (M/T
and A/T). Check sensor output voltage. To do so, disconnect voltmeter
positive lead from terminal "A" and connect it to terminal "C" (M/T),
or terminal "B" (A/T).
4) Maintain throttle plate in closed position (M/T and A/T).
Ensure throttle linkage contacts stop. Note voltmeter reading. Output
voltage should be .8 volt (M/T), or 4.2 volts (A/T).
5) If output voltage is incorrect, loosen bottom sensor
retaining screw and pivot sensor in adjustment slot for a coarse
adjustment. Loosen top sensor retaining screw for fine adjustments.
Tighten screws after adjustment.
TESTING & TROUBLE SHOOTING
PRELIMINARY CHECKS & PRECAUTIONS
Subsystem Checks
The following systems and components must be in good
condition and operating properly before assuming a fuel injection
system malfunction.
* Air filter.
* All support systems and wiring.

* Battery connections and specific gravity.
* Engine Compression.
* Electrical connections on components and sensors.
* Emission control devices.
* Ignition system.
* All vacuum line, fuel hose and pipe connections.
General Precautions
In order to prevent injury to operator or damage to system
or component parts, use following techniques:
* Turn ignition off before connecting or disconnecting any
component parts.
* DO NOT apply DC voltage greater than 12 volts or any AC voltage
to system.
* Disconnect battery cables before charging.
* Remove ECU from vehicle if ambient temperature could exceed
176

F (80

C).
* DO NOT modify or circumvent any system functions.
SYSTEM TESTING
Fuel System Test
WARNING: Always relieve residual fuel pressure in fuel delivery
system before opening system. To prevent chance of personal
injury, cover fittings with shop towel while disconnecting
fittings.
1) Remove cap from pressure test port located in fuel rail.
See Fig. 3. Connect Fuel Pressure Gauge (J-34730-1) to pressure
fitting.
2) Start vehicle. Pressure should be approximately 31 psi
(2.1 kg/cm

) with vacuum hose connected to pressure regulator and
39 psi (2.6 kg/cm

) with vacuum hose removed from pressure
regulator.
3) Check fuel pump flow rate. A good fuel pump will deliver
at least one liter of fuel per minute with fuel return line pinched
off. If fuel pump does not pump adequately, inspect fuel system for a
plugged fuel filter or filter sock.
Fig. 3: Fuel System Pressure Test Components
Courtesy of Chrysler Motors.
4) Fuel pump flow rate can be checked by connecting one end
of an old A/C gauge hose to fuel test port on fuel rail and inserting

other end of hose into a container of at least one liter or more
capacity.
5) Run fuel pump by installing a jumper wire into diagnostic
connector terminals D1-5 and D1-6. Be sure to pinch off fuel return
line or most of fuel will be returned to fuel tank.
EGR Solenoid Test
1) Verify that vacuum is present at vacuum fitting "C" of
EGR solenoid. See Fig. 4. Remove vacuum connector from "A" and "B".
Connect a vacuum gauge to "B".
2) Start and idle engine. There should be no vacuum at "B".
Disconnect electrical connector "D" from solenoid. There should now
be vacuum at "B".
Fig. 4: EGR Solenoid Test Points
Courtesy of Chrysler Motors.
MAP Sensor Test
1) Inspect MAP sensor hoses and connections. Repair as
necessary. With ignition on and engine off, test MAP sensor output
voltage at connector terminal "B". (Marked on sensor body). See
Fig. 5. Output voltage should be 4 to 5 volts.
2) To verify wiring harness condition, test ECU terminal C-6
for same voltage described. Test MAP sensor supply voltage at sensor
connector terminal "C" with ignition on.

3) Voltage should be 4.5-5.5 volts. Same voltage should also
be at terminal C-14 of ECU wire harness connector. Using Diagnostic
Tester (M.S. 1170), test MAP sensor ground circuit at terminal D-3
and terminal "A" of sensor connector.
4) Using an ohmmeter, test MAP sensor ground circuit at ECU
connector between terminal D-3 of ECU connector and terminal B-11
with an ohmmeter.
5) If ohmmeter or diagnostic tester indicates an open
circuit, inspect for a defective sensor ground connection, located on
right side of cylinder block. If ground connection is good, ECU may
need to be replaced.
Fig. 5: MAP Sensor Test Points
Courtesy of Chrysler Motors.
O2 Sensor Heating Element Test
Disconnect O2 sensor connector. Connect an ohmmeter to
terminals "A" and "B" only (marked on the connector) of O2 sensor
connector. Resistance should be between 5 and 7 ohms. Replace sensor
if ohmmeter indicates an infinity reading.
CTS Test

1) Disconnect wire harness connector from CTS sensor. Test
resistance of sensor with a high impedance digital ohmmeter.
Resistance should be less than 1000 ohms with engine warm. See
TEMPERATURE-TO-RESISTANCE VALUES table.
2) Test resistance of wire harness between ECU terminal D-3
and sensor connector terminal. Repeat test at terminal C-10 of ECU
and sensor connector terminal. Repair wire harness if an open circuit
is indicated.
MAT Sensor Test
1) Disconnect wire harness connector from MAT sensor. Test
resistance of sensor with a high impedance digital ohmmeter.
Resistance should be less than 1000 ohms with engine warm. Replace
sensor if resistance is not within specified range. See
TEMPERATURE-TO-RESISTANCE VALUES table.
2) Test resistance of wire harness between ECU wire harness
connector terminal D-3 and sensor connector terminal. Repeat test
with terminal C-8 at ECU and sensor connector terminal. Repair wire
harness if an open circuit or resistance is greater than one ohm is
indicated.
TPS Test
See THROTTLE POSITION SENSOR TEST PROCEDURE chart in this
article.
TEMPERATURE-TO-RESISTANCE VALUES (CTS & MAT SENSOR) TABLE


F

C Ohms
(Approximate)
212 .......................... 100 ........................... 185
160 .......................... 70 ............................ 450
100 .......................... 38 ........................... 1600
70 ........................... 20 ........................... 3400
40 ............................ 4 ........................... 7500
20 ........................... -7 ......................... 13,500
0 ............................ -18 ........................ 25,000
-40 .......................... -40 ....................... 100,700

Knock Sensor Test
1) Start engine until engine reaches normal operating
temperature. Connect Diagnostic Tester (M.S. 1700). Observe knock
value on tester. Using tip of screw driver, gently tap on cylinder
block next to knock sensor and observe knock sensor value on tester.
2) Knock sensor value should increase while tapping on
cylinder block. If knock sensor value does not increase while tapping
on cylinder block, check knock sensor for proper connection. If
connection is good, replace knock sensor.
Speed Sensor Test
Disconnect speed sensor connector from ignition control
module. Place an ohmmeter between terminals "A" and "B". (Marked on
connector) Reading should be 125-275 ohms with engine hot. Replace
sensor if readings are not within specifications.
Idle Speed Stepper (ISS) Motor
1) Set parking brake and block drive wheels. Route all
tester cables away from cooling fans, drive belts, pulleys and
exhaust system. Always allow engine speed to return to normal before
disconnecting testing tools.
2) With ignition off, disconnect ISS motor connector at

throttle body. Connect Exerciser Tool (Part No. 8980 002 646) into
ISS motor. See Fig. 6.
3) Connect Red clip to battery positive cable. Connect
Black clip to battery negative cable. Red light on exerciser tool
will illuminate when properly connected. Start engine.
NOTE: When switch on exerciser tool is in "High" or "Low"
position, light on exerciser tool will flash indicating
voltage pulses are being sent to ISS motor.
4) Move exerciser tool switch to "High" position. Engine
speed should increase. Move switch to "Low" position. Engine speed
should decrease. If engine speed increases or decreases while using
exerciser tool, ISS motor is functioning properly.
5) Disconnect exerciser tool and reconnect ISS motor
connector. If engine speed does not change, turn ignition off and
remove ISS motor from throttle body.
6) With ignition off, switch exerciser tool between "High"
and "Low" positions. Check movement of ISS motor pintle. Pintle
should move in and out. If pintle does not move, replace ISS motor.
7) Start engine and test new ISS motor for proper
operation. If pintle operates properly, check ISS motor bore in
throttle body for blockage and clean as necessary. Reinstall ISS
motor into throttle body.
Fig. 6: ISS Motor Test Connector
Courtesy of Chrysler Motors.
Fuel Injector Test

See FUEL INJECTOR TEST PROCEDURE chart in this article.
REMOVAL & INSTALLATION
COOLANT TEMPERATURE SENSOR (CTS)
Removal & Installation
Drain cooling system. Remove air cleaner assembly.
Disconnect CTS wire connector. Remove CTS from engine block. Install
replacement CTS and connect CTS wire connector. Install air cleaner
assembly. Fill cooling system.
OXYGEN SENSOR
Removal & Installation
Raise and support vehicle. Disconnect O2 sensor wire
connector. Remove O2 sensor from exhaust manifold. Install O2 sensor
and tighten to 30 ft. lbs. (41 N.m). Connect O2 sensor wire connector
and lower vehicle.
KNOCK SENSOR
Removal & Installation
Raise and support vehicle. Disconnect knock sensor wire
connector. Remove knock sensor from cylinder block. Install knock
sensor and connect knock sensor wire connector. Lower vehicle.
SPEED SENSOR
Removal & Installation
Disconnect speed sensor wire connector. Remove 2 speed
sensor retaining bolts at transmission housing. Install speed sensor
and connect speed sensor wire connector.
STARTER MOTOR RELAY
Removal & Installation
Disconnect negative battery cable. Identify, tag and
disconnect wiring to relay. Remove relay retaining screws and remove
relay from inner fender panel. Install replacement relay and connect
relay wires. Connect negative battery cable. Test relay operation.
MANIFOLD AIR/FUEL TEMPERATURE (MAT) SENSOR
Removal & Installation
Disconnect wire connector from MAT sensor. Remove MAT sensor
from intake manifold. To install, reverse removal procedure.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
Removal & Installation
Disconnect wire connector, vacuum hose, and retaining nuts
from MAP sensor. Remove sensor from firewall. To install, reverse
removal procedure.
FUEL INJECTOR
WARNING: Always relieve residual fuel pressure in fuel delivery
system before opening system. To prevent chance of personal
injury, cover fittings with shop towel while disconnecting
fittings.

Removal
Disconnect fuel lines from fuel rail assembly. Disconnect
injector wire harness connector. Remove fuel rail retaining bolts.
Remove vacuum hose from fuel pressure regulator valve. Remove fuel
injector retaining clips and remove fuel injectors. See Fig. 7. On
models with (A/T), it may be necessary to remove throttle pressure
cable and bracket to remove fuel rail assembly.
NOTE: O-rings must be replaced before fuel lines are reassembled.
Installation
Install fuel injectors into fuel rail assembly and install
retaining clips. Position fuel rail onto manifold while lining up
injectors with holes in intake manifold. Secure injector retaining
bolts. Connect injector wire connectors to proper injectors. Install
fuel lines into fuel rail assembly. Connect vacuum hose to pressure
regulator. Install throttle pressure bracket and cable (A/T).
Fig. 7: Fuel Rail Assembly
Courtesy of Chrysler Motors.

FUEL PRESSURE REGULATOR
WARNING: Always relieve residual fuel pressure in fuel delivery
system before opening system. To prevent chance of personal
injury, cover fittings with shop towel while disconnecting
fittings.
Removal & Installation
Remove injector fuel rail assembly. Remove 2 pressure
regulator retaining screws. Remove regulator from fuel rail. To
install, reverse removal procedure. Adjust regulator after
installation.
IDLE SPEED STEPPER (ISS) MOTOR
Removal & Installation
1) Disconnect ISS motor connector. Remove ISS motor
retaining screws and ISS motor. To install, reverse removal
procedure. No idle speed adjustment is necessary. Idle speed is
controlled by the Electronic Control Unit (ECU).
THROTTLE POSITION SENSOR
Removal & Installation
Disconnect TPS wire connector. Bend retaining bolts lock
tabs and remove retaining bolts. Remove TPS from throttle plate
assembly. To install, reverse removal procedure. Adjust TPS after
installation. See ADJUSTMENTS in this article.
EGR VALVE
Removal & Installation
Disconnect vacuum hose from EGR valve. Remove bolts which
hold EGR valve to intake manifold. Remove valve and discard gasket.
Clean intake manifold gasket mating surface. To install valve,
reverse removal procedure. Always use new gasket. See Fig. 8.

Fig. 8: EGR Valve
Courtesy of Chrysler Motors.
EGR SOLENOID

Disconnect solenoid vacuum hoses. Disconnect solenoid wiring
connector. Remove solenoid retaining bolts and solenoid. To install
valve, reverse removal procedure.
ECU CONNECTOR PIN IDENTIFICATION 24-PIN CONNECTOR MPFI TABLE

Terminal No. Wire Function
A1 .................................................. Injector No. 3
A2 .................................................. Injector No. 6
A3 .................................................. Injector No. 2
A4 .................................................. Injector No. 4
A5 ................................................. Fuel Pump Relay
A6 ........................................................ Not Used
A7 ............................................. Oxygen Sensor Relay
A8 ..................................................... Shift Light
A9 ..................................................... Latch Relay
A10 ............................................. EGR/Evap. Solenoid
A11 ....................................................... Not Used
A12 ...................................................... A/C Relay
B1 .................................................. Injector No. 1
B2 .................................................. Injector No. 5
B3 ........................................................... AIS A
B4 .......................................................... AIS A1
B5 ........................................................... AIS C
B6 .......................................................... AIS C1
B7 .................................................. Battery (Pos.)
B8 ........................................................ Ignition
B9 ........................................................ Not Used
B10 ............................................... Latched B (Pos.)
B11 ......................................................... Ground
B12 ......................................................... Ground

Fig. 9: Multi-Point Injection ECU Connector
Courtesy of Chrysler Motors.
ECU CONNECTOR PIN IDENTIFICATION 32-PIN CONNECTOR MPFI TABLE

Terminal No. Wire Function
C1 ............................................. Speed Sensor (Pos.)
C2 ..................................................... A/C Request
C3 ........................................................... Start
C4 ...................................................... P/N Switch
C5 .................................................... Sync. (Neg.)

C6 ...................................................... MAP Sensor
C7 ...................................................... TPS Sensor
C8 ................................................ Air Temp. Sensor
C9 ........................................................ Not Used
C10 ........................................... Coolant Temp. Sensor
C11 ............................................... Injection Supply
C12 ................................................. TX Serial Data
C13 ....................................................... Not Used
C14 ...................................... MAP Sensor Supply Voltage
C15 ............................................. TPS Supply Voltage
C16 ................................................... Sync. (Pos.)
D1 ............................................. Speed Sensor (Neg.)
D2 ...................................................... A/C Select
D3 ................................................... Sensor Ground
D4 ........................................................ Not Used
D5 ........................................................ Not Used
D6 ........................................................ Not Used
D7 ........................................................ Not Used
D8 ............................................. Knock Sensor Ground
D9 ............................................. Oxygen Sensor Input
D10 ................................................ Injector Supply
D11 ................................................. RX Serial Data
D12 ....................................................... Not Used
D13 .................................................... Spark/Dwell
D14 ....................................................... Not Used
D15 ....................................................... Not Used
D16 ................................................... Knock Sensor

Fig. 10: Multi-Point Injection Diagnostic Connector
Courtesy of Chrysler Motors.

Fig. 11: Comanche Multi-Point Fuel Injection Wiring Diagram
(Wiring Diagram Not Available for Cherokee & Wagoneer Models)

Fig. 12: Throttle Position Sensor Test Procedure Chart (M/T)

Fig. 13: Fuel Injector Test Procedure Chart