sensor JEEP CHEROKEE 1988 Service Owner's Manual
[x] Cancel search | Manufacturer: JEEP, Model Year: 1988, Model line: CHEROKEE, Model: JEEP CHEROKEE 1988Pages: 1378, PDF Size: 19.9 MB
Page 77 of 1378
![JEEP CHEROKEE 1988 Service Owners Manual 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 Owners Manual 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
Page 79 of 1378
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 80 of 1378
Fig. 4: MAP Sensor Terminal Identification
Oxygen Sensor
Oxygen sensor must be tested with System Tester (M.S. 1700).
Oxygen Sensor Heating Element
Disconnect electrical connector from oxygen sensor. Using an
ohmmeter, measure resistance between connector terminals "A" and "B"
(marked on connector). See Fig. 5. If resistance is not 5-7 ohms,
replace sensor.
Page 81 of 1378
Fig. 5: Testing Oxygen Sensor Heating
Element Resistance
Knock Sensor
Knock sensor must be tested with System Tester (M.S. 1700).
Speed Sensor
Disconnect speed sensor electrical connector from the sensor.
Using an ohmmeter, measure resistance between connector terminals "A"
and "B" (marked on connector). If reading is not 125-275 ohms with
engine at normal operating temperature, replace speed sensor.
"Synch Pulse" (Stator)
1) Using an analog voltmeter, insert positive probe into Blue
wire at distributor connector. Insert negative probe into Gray wire
with tracer at distributor connector.
NOTE: Do not remove connector from distributor. Insert voltmeter
leads from rear of connector. Do not puncture wire.
2) With voltmeter set on "15-Volt A/C" scale, turn ignition
on. Voltmeter should indicate 5 volts. If voltage is indicated, go to
step 4). If no voltage is indicated, check voltmeter leads for good
connection and go to next step.
3) If there is still no voltage reading, turn ignition off
and remove ECU. Reconnect harness and turn ignition off and remove
ECU. Reconnect harness and turn ignition on. Check for voltage between
ECU pin "C-16" and good ground. If voltage still does not register,
test system with System Tester (M.S. 1700).
4) If 5 volts was detected, check for continuity at the
following points:
* Between Blue wire at distributor connector and terminal "C-16"
at ECU.
* Between Gray wire with tracer at distributor connector and
terminal "C-5" at ECU.
* Between Black wire at distributor connector and good ground.
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 85 of 1378
Fig. 8: Throttle Position Sensor Diagnostics
Page 90 of 1378
![JEEP CHEROKEE 1988 Service Owners Manual AB BREVIA TIO NS
1988 J e ep C hero ke e
GENERAL INFORMATION
COMMONLY USED ABBREVIATION
"A" ABBREVIATION TABLE
"A" ABBREVIATION TABLE \](/img/16/57037/w960_57037-89.png "JEEP CHEROKEE 1988 Service Owners Manual 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
Page 91 of 1378
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ABBREVIATION DEFINITION](/img/16/57037/w960_57037-90.png "JEEP CHEROKEE 1988 Service Owners Manual \
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ABBREVIATION DEFINITION")
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ABBREVIATION DEFINITION
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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
"C" ABBREVIATION TABLE \
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ABBREVIATION DEFINITION
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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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"D" ABBREVIATION TABLE
"D" ABBREVIATION TABLE \
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"D" Drive
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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ABBREVIATION DEFINITION
Page 93 of 1378
![JEEP CHEROKEE 1988 Service Owners Manual \
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EAC Electric Assist Choke")
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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" ABBREVIATION TABLE
"F" ABBREVIATION TABLE \
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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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ABBREVIATION DEFINITION