lock JEEP CHEROKEE 1988 Service User Guide
[x] Cancel search | Manufacturer: JEEP, Model Year: 1988, Model line: CHEROKEE, Model: JEEP CHEROKEE 1988Pages: 1378, PDF Size: 19.9 MB
Page 75 of 1378
ECU signal line and the other end connected to ground. As throttle
valve angle changes, a return voltage is sent back to the ECU through
the third wire. Output voltage to the ECU is about one volt when
throttle valve is at idle position, and about 5 volts when throttle
valve is at wide open throttle.
A dual TPS is used on automatic transmission equipped models.
The additional sensor provides throttle position information to the
transmission.
Knock Sensor
A knock sensor is mounted on the lower left side of block,
just above the oil pan. This sensor detects abnormal engine vibration
due to "detonation" and/or "pre-ignition". The knock sensor supplies
detonation information to the ECU. The ECU then alters ignition timing
as needed to maintain maximum timing under most operating conditions.
Park/Neutral (P/N) Switch
The P/N switch is mounted in automatic transmission equipped
vehicles. The switch indicates when the transmission is in Park or
Neutral.
Speed Sensor
The speed sensor is a nonadjustable sensor attached to the
flywheel/drive plate housing with special shoulder bolts. This sensor
provides Top Dead Center (TDC) and engine speed information to the ECU\
by counting the flywheel teeth as they pass during engine operation.
The flywheel has a large trigger tooth and notch located 12 small
teeth before each TDC position. See Fig. 2.
Fig. 2: Design of Speed Sensor
When a small tooth and notch pass the magnetic core of the
sensor, the concentration and collapse of the magnetic field created
induces a small voltage spike into the sensor pick-up coil windings.
Page 77 of 1378
![JEEP CHEROKEE 1988 Service User Guide proper increased enrichment for the next engine start. Idle speed is
nonadjustable.
EMISSION CONTROL
The ECU electrically controls Exhaust Gas Recirculation (EGR).\
An ECU-controlled](/img/16/57037/w960_57037-76.png "JEEP CHEROKEE 1988 Service User Guide proper increased enrichment for the next engine start. Idle speed is
nonadjustable.
EMISSION CONTROL
The ECU electrically controls Exhaust Gas Recirculation (EGR).\
An ECU-controlled")
proper increased enrichment for the next engine start. Idle speed is
nonadjustable.
EMISSION CONTROL
The ECU electrically controls Exhaust Gas Recirculation (EGR).\
An ECU-controlled solenoid valve is used to control EGR valve
function. This valve is located on the left inner fender panel and is
operated by the ECU in response to coolant temperature, throttle
position, and manifold pressure.
Under conditions of engine warm-up, engine idle, wide open
throttle, or rapid acceleration/deceleration, the solenoid valve is
energized, blocking vacuum to the EGR valve. At normal operating
temperatures with engine speed above idle, the solenoid valve is de-
energized, allowing normal EGR valve function.
NOTE: If the electrical connector is removed from the EGR solenoid,
EGR flow will be allowed at all times.
A/C CLUTCH CONTROL
The ECU controls the A/C compressor clutch to improve idle
quality. The A/C compressor clutch will be engaged or disengaged as
deemed necessary by the ECU through the A/C clutch relay.
SHIFT LIGHT CONTROL
The shift light system is used on all manual transmission
equipped vehicles. The ECU monitors coolant temperature, throttle
position, vehicle speed, and engine speed to control the shift light.
The ECU calculates what gear position the vehicle should be in and
uses this information to turn on the light. The light indicates the
best shift point to the driver for maximum fuel economy.
The light is tested when the ignition switch is turned on.
When the engine is started, the light should go out. A transmission-
mounted switch prevents the light from illuminating when the
transmission is shifted into high gear. The ECU turns the light off if
the shift to the next higher gear is not performed within 3-5 seconds
after light comes on.
DIAGNOSIS & TESTING
PRELIMINARY CHECKS
Before assuming that the ECU is faulty, the following systems
and components must be in good condition and operating properly:
* Air filter.
* All support systems and wiring.
* Battery connections and specific gravity.
* Compression pressure.
* Electrical and vacuum connections to components, sensors and
switches.
* Emission control devices.
* Ignition system.
* All vacuum and fuel line (hose) connections.
FUEL SYSTEM TEST
Fuel Pressure
1) Remove cap from pressure test port on fuel rail and
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COMPONENT TESTING
Throttle Position Sensor
See THROTTLE POSITION SENSOR DIAGNOSTICS chart near the end
of this article. See Fig. 8.
Coolant Temperature Sensor (CTS) &
Manifold Air Temperature (MAT) Sensor
1) Disconnect the electrical connector from the sensor. Using
a high impedance, digital volt/ohmmeter, measure the resistance of the
sensor. If measured resistance is not as specified, replace sensor.
See the CTS & MAT SENSOR TEMPERATURE-TO-RESISTANCE VALUE table.
2) Test electrical harness resistance of both sensors by
testing between ECU harness connector "D-3" and sensor connector. Also
test between sensor connector and ECU harness connector "C-10" ("C-8"
on MAT sensor). Repair wire if open circuit is detected. Repair MAT
sensor wiring harness if resistance is greater than one ohm.
CTS & MAT SENSOR TEMPERATURE-TO-RESISTANCE VALUE
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F(C) Ohms
212 (100) .................................. 185
160 (71) ................................... 450
100 (38) .................................. 1600
70 (21) ................................... 3400
40 (4) .................................... 7500
20 (-7) ................................. 13,500
0 (-18) ................................. 25,000
-40 (-40) .............................. 100,700
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Manifold Absolute Pressure (MAP) Sensor
NOTE: Terminal identification letters are stamped on MAP sensor
body.
1) Disconnect electrical connector from sensor. With ignition
on and engine stopped, measure voltage output of sensor terminal "B".
See Fig. 4 . Ensure wiring harness is okay by also measuring voltage at
ECU terminal "C-t". Output voltage should be 4-6 volts at both points.
Repair or replace wiring harness as required.
2) With ignition on and engine stopped, measure supply
voltage of sensor terminal "C". See Fig. 4. Ensure wiring harness is
okay by also measuring voltage at ECU terminal "C-14". Supply voltage
should be 4.4-5.5 volts at both points. Repair or replace wiring
harness as required.
3) Using an ohmmeter, measure ground circuit resistance at
sensor terminal "A" and ECU connector terminal "D-3". Ensure wiring
harness is okay by also measuring resistance between ECU terminal "D-
3" and "B-11". If ohmmeter indicates an open circuit, check for
defective sensor ground connection at right side of cylinder block.
4) If ground connection is okay, replace ECU. If ECU terminal
"D-3" has short to 12-volts, repair wire before replacing ECU. Repair
or replace wiring harness as required.
Page 84 of 1378
ELECTRONIC CONTROL UNIT (ECU)
Removal & Installation
Information not available from manufacturer.
COOLANT TEMPERATURE SENSOR (CTS)
Removal & Installation
Drain cooling system. Remove air cleaner assembly. Disconnect
electrical connector and remove sensor from block. To install, reverse
removal procedure. Refill cooling system.
OXYGEN (O2) SENSOR
Removal & Installation
Raise and support vehicle. Disconnect electrical connector
from sensor. Remove sensor from exhaust manifold. Install and tighten
sensor to 35 ft. lbs. (47 N.m). Reconnect electrical connector. Lower
vehicle.
THROTTLE POSITION SENSOR (TPS)
Removal
Disconnect electrical connector from TPS. Bend lock tabs away
from retaining screws and remove screws. Remove TPS.
Installation
With throttle valve in normal closed position, install TPS.
Install TPS retaining screws. Perform OUTPUT CHECK.
NOTE: Throttle position sensor is nonadjustable. Only output
voltage can be monitored.
Output Check (Manual Transmission Only)
1) Connect negative lead of digital voltmeter to terminal "B"
and positive lead to terminal "A" of TPS connector. Do not disconnect
electrical connector. Insert leads through back of connector. It may
be necessary to remove throttle body from vehicle to gain access to
connector.
2) Turn ignition on, engine off. With throttle closed and
resting against idle stop, input voltage should be about 5 volts. Move
positive lead from terminal "B" to terminal "C" and read voltage
output. Output voltage should be about 0.8 volt with throttle closed
and resting against idle stop.
3) If voltage is not as specified, loosen lower retaining
screw and pivot sensor for large adjustments. Loosen upper retaining
screw and pivot sensor for small adjustments. Adjust sensor so output
voltage reading equals 16 percent of input voltage. If voltage
specifications cannot be obtained, replace sensor. Remove voltmeter.
Tighten screws and bend retaining tabs into position.
ALL OTHER SENSORS, SOLENOIDS & SWITCHES
Removal & Installation
Removal of sensors, switches, and solenoids is accomplished
by disconnecting the electrical and/or vacuum connectors and removing
or detaching the component. To install, reverse removal procedure.
TESTING
NOTE: Refer to Figs. 8-10 for Testing information.
Page 90 of 1378
![JEEP CHEROKEE 1988 Service User Guide AB BREVIA TIO NS
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GENERAL INFORMATION
COMMONLY USED ABBREVIATION
"A" ABBREVIATION TABLE
"A" ABBREVIATION TABLE \](/img/16/57037/w960_57037-89.png "JEEP CHEROKEE 1988 Service User Guide AB BREVIA TIO NS
1988 J e ep C hero ke e
GENERAL INFORMATION
COMMONLY USED ABBREVIATION
\"A\" ABBREVIATION TABLE
\"A\" ABBREVIATION TABLE \")
AB BREVIA TIO NS
1988 J e ep C hero ke e
GENERAL INFORMATION
COMMONLY USED ABBREVIATION
"A" ABBREVIATION TABLE
"A" ABBREVIATION TABLE \
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ABBREVIATION DEFINITION
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A Amperes
A/C Air Conditioning
A/T Automatic Transmission/Transaxle
AAP Auxiliary Accelerator Pump
AB Air Bleed
ABCV Air Bleed Control Valve
ABDC After Bottom Dead Center
ABRS Air Bag Restraint System
ABS Anti-Lock Brake System
AC Alternating Current
ACC A/C Clutch Compressor
ACCS A/C Cycling Switch
ACCUM Accumulator
ACCY Accessory
ACT Air Charge Temperature Sensor
ACV Thermactor Air Control Valve
ADJ Adjust or Adjustable
ADV Advance
AFS Airflow Sensor
AI Air Injection
AIR or A.I.R. Air Injection Reactor
AIS Air Injection System
ALCL Assembly Line Communications Link
ALDL Assembly Line Diagnostic Link
ARC Automatic Ride Control
ASCD Automatic Speed Control Device
ASCS Air Suction Control Solenoid
ASD Auto Shutdown
ASDM Air Bag System Diagnostic Module
ASV Air Suction Valve
ATC Automatic Temperature Control
ATDC After Top Dead Center
ATF Automatic Transmission Fluid
ATS Air Temperature Sensor
AXOD Automatic Transaxle Overdrive
Abs. Absolute
Accy. Accessory
Alt. Alternator or Altitude
Amp. Ampere
Assy. Assembly
Auto. Automatic
Aux. Auxiliary
Avg. Average
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"B" ABBREVIATION TABLE
"B" ABBREVIATION TABLE
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B/P Backpressure
BAC By-Pass Air Control
BAP Barometric Absolute Pressure Sensor
BARO Barometric
BBDC Before Bottom Dead Center
BCM Body Control Module
BDC Bottom Dead Center
BHP Brake Horsepower
BLK Black
BLU Blue
BMAP Barometric & Manifold Absolute Pressure Sensor
BOO Brake On-Off Switch
BP Barometric Pressure sensor
BPS Barometric Pressure Sensor
BPT Backpressure Transducer
BRN Brown
BTDC Before Top Dead Center
BTU British Thermal Unit
BVSV Bimetallic Vacuum Switching Valve
Baro. Barometric
Batt. Battery
Bbl. Barrel (Example: 4-Bbl.)
Blst. Ballast
Blwr. Blower
Brkr. Breaker
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"C" ABBREVIATION TABLE
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C Celsius (Degrees)
C(3) I Computer Controlled Coil Ignition
C(4) Computer Controlled Catalytic Converter
CANP Canister Purge solenoid
CARB California Air Resources Board
CAT Catalytic Converter
CB Circuit Breaker
CBD Closed Bowl Distributor
CBVV Carburetor Bowl Vent Valve
cc Cubic Centimeter
CCC Computer Command Control
CCD Computer Controlled Dwell
CCM Central Control Module
CCO Converter Clutch Override
CCOT Cycling Clutch Orifice Tube
CCW Counterclockwise
CDI Capacitor Discharge Ignition
CEC Computerized Engine Control
CFI Central Fuel Injection
CID Cubic Inch Displacement
CID Cylinder Identification sensor
CIS Continuous Injection System
CIS-E Continuous Injection System-Electronic
CKT Circuit
CLR Clear
CNG Compressed Natural Gas
Page 92 of 1378
CO Carbon Monoxide
CO2 Carbon Dioxide
CONV Convertible
CP Canister Purge
CPA Connector Position Assurance
CPS Crank Position Sensor
CTS Coolant Temperature Sensor
CV Check Valve or Constant Velocity
CVC Constant Vacuum Control
CW Clockwise
CYL or Cyl. Cylinder
Calif. California
Carb. Carburetor
Chrg. Charging
Circ. Circuit
Cntrl. Control
Comp. Compressor or Compartment
Conn. Connector
Cont. Continued
Conv. Convertible or Converter
Cu. In. Cubic Inch
Cyl. Cylinder
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DBC Dual Bed Catalyst
DC Direct Current or Discharge
DDD Dual Diaphragm Distributor
DERM Diagnostic Energy Reserve Module
DFI Digital Fuel Injection
DIC Driver Information Center
DIS Direct Ignition System
DIS Distributorless Ignition System
DIST Distribution
DISTR Distributor
DK BLU Dark Blue
DK GRN Dark Green
DME Digital Motor Electronics (Motronic System)
DOHC Double Overhead Cam
DOT Department of Transportation
DP Dashpot
DRB-II Diagnostic Readout Box
DVOM Digital Volt/Ohm Meter (see VOM)
Def. Defogger or Defroster
Def. Defrost
Defog. Defogger
Diag. Diagnostic
Dist. Distributor or Distribution
Dr. Door
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"E" ABBREVIATION TABLE
"E" ABBREVIATION TABLE \
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EAC Electric Assist Choke
EACV Electric Air Control Valve
EBCM Electronic Brake Control Module
ECA Electronic Control Assembly
ECAT Electronically Controlled Automatic Transaxle
ECM Electronic Control Module
ECT Engine Coolant Temperature Sensor
ECU Electronic Control Unit or Engine Control Unit
EDF Electric Drive Fan relay assembly
EDIS Electronic Distributorless Ignition System
EEC Electronic Engine Control
EECS Evaporative Emission Control System
EEPROM Electronically Erasable PROM
EFE Early Fuel Evaporation
EFI Electronic Fuel Injection
EGO Exhaust Gas Oxygen sensor (see HEGO)
EGR Exhaust Gas Recirculation system
EGRC EGR Control solenoid or system
EGRV EGR Vent solenoid or system
EMR Emission Maintenance Reminder Module
ESA Electronic Spark Advance
ESC Electronic Spark Control
EST Electronic Spark Timing
ETR Emergency Tensioning Retractor
EVAP Fuel Evaporative System
EVIC Electronic Vehicle Information Center
EVO Electronic Variable Orifice
EVP EGR Valve Position Sensor
EVR EGR Valve Regulator
EVRV Electronic Vacuum Regulator Valve
Elect. Electronic
Eng. Engine
Evap. Evaporative
Exc. Except
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F Fahrenheit (Degrees)
F/B Fuse Block
FBC Feedback Carburetor
FI Fuel Injector or Fuel Injection
FICD Fast Idle Control Device
FIPL Fuel Injector Pump Lever
FP Fuel Pump
FPM Fuel Pump Monitor
FPR-VSV Fuel Pressure Regulator Vacuum Switching Valve
FWD Front Wheel Drive
Fed. Federal
Ft. Lbs. Foot Pounds
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"G" ABBREVIATION TABLE
"G" ABBREVIATION TABLE \
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Ign. Ignition
In. Inches
Inj. Injector
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J/B Junction Block
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k/ohms 1000 ohms (kilo as in k/ohms)
kg Kilograms (weight)
kg/cm Kilograms Per Square Centimeter
KAM Keep Alive Memory
KAPWR Keep Alive Power
KM/H Kilometers Per Hour
KOEO Key On Engine Off
KOER Key On Engine Running
KS Knock Sensor
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"L" ABBREVIATION TABLE
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L Liter(s)
L/D Light Duty
LCD Liquid Crystal Display
LED Light Emitting Diode
LH Left Hand
LOS Limited Operation Strategy
LT BLU Light Blue
LT GRN Light Green
LUS Lock-Up Solenoid
Lbs. Pounds
Lt(s). Light(s)
Lugg. Luggage
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"M" ABBREVIATION TABLE
"M" ABBREVIATION TABLE \
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mA Milliamps
mV Millivolts
mfd. Microfarads
Page 97 of 1378
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"P" ABBREVIATION TABLE
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"P" Park
P/C Printed Circuit
P/N Park/Neutral
P/S Power Steering
PAV Pulse Air Valve
PC-SOL Purge Control Solenoid
PCM Powertrain Control Module
PCS Purge Control Solenoid
PCSDM Passenger Compartment Sensor/Diagnostic Module
PCV Positive Crankcase Ventilation
PFE Pressure Feedback EGR sensor or circuit
PFI Port Fuel Injection (see MA SEFI)
PGM-CARB Programmed Carburetor
PGM-FI Programmed Fuel Injection
PIP Profile Ignition Pickup
PNK Pink
PPL Purple
PRNDL Park Reverse Neutral Drive Low
PROM Programmable Read-Only Memory
psi Pounds Per Square Inch
PSPS Power Steering Pressure Switch
PTC Positive Temperature Coefficient
PTO Power Take-Off
PWR GND Power Ground circuit
Pkg. Package
Press. Pressure
Prog. Programmed or Programmable
Pts. Pints
Pwr. Power
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"Q" ABBREVIATION TABLE
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"R" ABBREVIATION TABLE
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RABS Rear Anti-Lock Brake System
RAC Remote Accessory Control
RAM Random Access Memory
RAP Retained Accessory Power
RECIRC Recirculation
RED Red
RH Right Hand
ROM Read Only Memory
RPM Revolutions Per Minute