1988 JEEP CHEROKEE heating

Standards as part of the inspection process and for communicating
their findings to their customers.
The Motorist Assurance Program continues to work
cooperatively and proactively with government agencies and consumer
groups toward solutions that both benefit the customer and are
mutually acceptable to both regulators and industry. We maintain the
belief that industry must retain control over how we conduct our
business, and we must be viewed as part of the solution and not part
of the problem. Meetings with state and other government officials
(and their representatives), concerned with auto repair and/or
consumer protection, are conducted. Feedback from these sessions is
brought back to the association, and the program adjusted as needed.
To assure auto repair customers recourse if they were not
satisfied with a repair transaction, the Motorist Assurance Program
offers mediation and arbitration through MAP/BBB-CARE and other non-
profit organizations. MAP conducted pilot programs in twelve states
before announcing the program nationally in October, 1998. During the
pilots, participating repair shops demonstrated their adherence to the
Pledge and Standards and agreed to follow the UICS in communicating
the results of their inspection to their customers. To put some
"teeth" in the program, an accreditation requirement for shops was
initiated. The requirements are stringent, and a self-policing method
has been incorporated which includes the "mystery shopping" of
outlets.
We welcome you to join us as we continue our outreach... with
your support, both the automotive repair industry and your customers
will reap the benefits. Please visit MAP at our Internet site www.
motorist.org or contact us at:
1444 I Street, NW Suite 700
Washington, DC 20005
Phone (202) 712-9042 Fax (202) 216-9646
January 1999
MAP UNIFORM INSPECTION GENERAL GUIDELINES
OVERVIEW OF SERVICE REQUIREMENTS AND SUGGESTIONS
It is MAP policy that all exhaust, brake, steering,
suspension, wheel alignment, drive-line, engine performance and
maintenance, and heating, ventilation and air conditioning, and
electrical services be offered and performed under the standards and
procedures specified in these sections.
Before any service is performed on a vehicle, an inspection
of the appropriate system must be performed. The results of this
inspection must be explained to the customer and documented on an
inspection form. The condition of the vehicle and its components will
indicate what services/part replacements may be "Required" or
"Suggested". In addition, suggestions may be made to satisfy the
requests expressed by the customer.
When a component is suggested or required to be repaired or
replaced, the decision to repair or replace must be made in the
customer's best interest, and at his or her choice given the options
available.
This section lists the various parts and conditions that
indicate a required or suggested service or part replacement.
Although this list is extensive, it is not fully inclusive. In
addition to this list, a technician may make a suggestion. However,
any suggestions must be based on substantial and informed experience,
or the vehicle manufacturer's recommended service interval and must be
documented.
Some conditions indicate that service or part replacement is

loose .................. A ... Require repair or replacement
of injection tube or
replacement of catalytic
converter.
Air injection tube
restricted ............. A ... Require repair or replacement
of injection tube or
replacement of catalytic
converter.
Air injection tube
threads damaged ........ A ... Require repair or replacement
of injection tube or
replacement of catalytic
converter.
Air injection tube
threads stripped
(threads missing) ...... A ... Require repair or replacement
of injection tube or
replacement of catalytic
converter.
Body cracked ............ B .. Require repair or replacement.
Converter empty ......... A .. Require repair or replacement.
Converter fill plug
missing ................ C .. Require repair or replacement.
Converter missing ....... C ............ Require replacement.
Exhaust gases leaking ... A .. Require repair or replacement.
Flanges leaking ......... A ... Require repair or replacement
of flanges.
Inlet pipes cracked ..... B .. Require repair or replacement.
Internal rattle (except
pellet-type) ........... 2 .......... (1) Further inspection
required.
Mounting brackets that
are part of converter
broken ................. A .. Require repair or replacement.
Obvious overheating ..... .. ......... ( 2) Require testing of
converter.
Outlet pipes cracked .... B .. Require repair or replacement.
Pieces of catalyst
material found
downstream ............. 1 ............ Suggest replacement.
Plugged ................. A ........ ( 3) Require replacement.
Testing has determined
that existing converter
has been lead-poisoned,
contaminated, or failed
testing ................ A .. Require repair or replacement.
( 1) - If the converter is breaking up, suggest converter
replacement. If an object has fallen into the converter,
remove the object.
( 2) - Overheating is caused by something other than the
converter. Further diagnosis is required to determine
the cause of the overheating.
( 3) - Determine cause and correct to ensure that new converter
will not become plugged.









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EXHAUST AND TAIL PIPES
NOTE: For pipes with resonators, also see MUFFLERS AND RESONATORS.
EXHAUST AND TAIL PIPE INSPECTION

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

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

Electric roller type fuel pump is located in fuel tank.
Integral check valve is used to maintain pressure in fuel delivery
system after pump stops running. Fuel pump operation is controlled by
ECU through a fuel pump relay.
IDLE SPEED ACTUATOR (ISA) MOTOR
ISA motor acts as movable idle stop to change throttle stop
angle. Both engine idle speed and deceleration throttle stop angle
are set by ISA. ECU controls ISA motor by providing appropriate
voltage outputs to produce idle speed or throttle stop angle required
for engine operating condition.
OXYGEN (O2) SENSOR
Oxygen sensor is equipped with a heating element that keeps
sensor at proper operating temperature at all times. Oxygen sensor is
located in exhaust pipe.
Maintaining proper sensor temperature at all times, system
enters "Closed Loop" operation sooner and remains in "Closed Loop"
during periods of extended idle. Electrical feed to oxygen sensor is
through ignition switch.
The ECU receives sensor voltage signal which varies with
oxygen content in exhaust gas. Signal is used by ECU as reference for
setting air/fuel mixture ratio. ECU varies voltage to injector both
to compensate for battery voltage fluctuations and to change duration
of injector opening for control of air/fuel mixture.
MANIFOLD AIR/FUEL TEMPERATURE (MAT) SENSOR
MAT sensor provides a signal to ECU that changes depending
upon temperature of air/fuel mixture in intake manifold. During high
temperature conditions, ECU will compensate for changes in density of
air.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
MAP sensor measures absolute pressure in intake manifold.
Both mixture density and ambient barometric pressure are supplied to
ECU by MAP sensor. Sensor is mounted in middle of firewall in engine
compartment. Sensor receives manifold pressure information through
vacuum line from throttle body. See Fig. 1.
Fig. 1: Manifold Absolute Pressure (MAP) Sensor
Courtesy of Chrysler Motors.
COOLANT TEMPERATURE SENSOR (CTS)

IDLE SPEED ACTUATOR (ISA) MOTOR
1) Adjust ISA motor plunger to establish initial position of
plunger only if motor has been removed or replaced. Remove air filter
elbow and start engine. Run engine until engine reaches normal
operating temperature. Turn A/C off (if equipped).
2) Connect tachometer leads to diagnostic connector D1,
attaching negative lead to terminal D1-3 and positive lead to
terminal D1-1. See Fig. 4. Turn ignition off. ISA motor plunger
should move to fully extended position.
3) When ISA motor plunger is fully extended, disconnect ISA
motor wiring connector and start engine. Engine speed should be
3300-3700 RPM. If incorrect, turn hex head screw at end of plunger to
provide engine speed of 3500 RPM.
4) Fully retract ISA motor by holding closed throttle (idle)\
switch plunger inward as throttle is opened. Closed throttle switch
plunger should not touch throttle lever in closed position. If
contact is made, check linkage and/or cable for binding or damage.
Repair as necessary.
5) Connect ISA motor wiring harness connector and turn
ignition off for 10 seconds. ISA motor should move to fully extended
position. Start engine. Engine speed should be 3500 RPM for short
period of time and then decrease to normal idle speed.
6) Turn ignition off. Disconnect tachometer. After final
adjustment of ISA motor, use thread penetrating sealant (Loctite 290)
on adjustment screw to prevent movement and maintain adjustment.
NOTE: If adjustment screw must be moved after thread sealant
hardens, loosen threads by heating screw with flameless heat
such as soldering gun. DO NOT use flame or torch type of
heat as damage to ISA motor will result.
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.
1) Replacement fuel pressure regulator must be adjusted to
establish correct pressure. Remove air filter elbow and hose. Connect
tachometer leads to diagnostic connector D1, attaching negative lead
to terminal D1-3 and positive lead to terminal D1-1. See Fig. 4.
Remove screw plug and install fuel pressure test fitting.
NOTE: Fuel pressure test fitting is not included with throttle
body. Fitting (8983 501 572) must be obtained separately.
2) Connect fuel pressure gauge to test fitting. Start engine
and increase speed to approximately 2000 RPM. Turn Torx head screw at
bottom of regulator to set correct pressure. Turning screw inward
increases pressure and turning screw outward decreases pressure. See
Fig. 3 .
3) All models require fuel pressure of 14.5 psi (1.0 kg/cm
).
Install lead sealing ball to cover regulator adjustment
screw after adjusting fuel pressure. Turn ignition off. Remove
measuring equipment and test fitting. Install original plug screw and
air filter assembly.

REFILLING
To prevent air from being trapped in engine block, engine
should be running when refilling cooling system. After system is full,
continue running engine until thermostat is open, then recheck fill
level. Do not overfill system.
TESTING
THERMOSTAT
1) Visually inspect thermostat for corrosion and proper
sealing of valve and seat. If okay, suspend thermostat and thermometer
in a 50/50 mixture of coolant and water. See Fig. 1. Do not allow
thermostat or thermometer to touch bottom of container. Heat water
until thermostat just begins to open.
2) Read temperature on thermometer. This is the initial
opening temperature and should be within specification. Continue
heating water until thermostat is fully open and note temperature.
This is the fully opened temperature. If either reading is not to
specification, replace thermostat.
Fig. 1: Testing Thermostat in Anti-Freeze/Water Solution
PRESSURE TESTING
A pressure tester is used to check both radiator cap and

computers may lose memory data. When battery power is
restored, driveability problems may exist on some vehicles.
These vehicles may require a relearn procedure. See COMPUTER
RELEARN PROCEDURES article in GENERAL INFORMATION section.
REPLACING BLOWN FUSES
Before replacing a blown fuse, remove ignition key, turn off
all lights and accessories to avoid damaging the electrical system. Be
sure to use fuse with the correct indicated amperage rating. The use
of an incorrect amperage rating fuse may result in a dangerous
electrical system overload.
BRAKE PAD WEAR INDICATOR
Indicator will cause a squealing or scraping noise, warning
that brake pads need replacement.
BRAKE WARNING LIGHT
CAUTION: If BRAKE warning light is on with parking brake disengaged
and engine running, there may be a problem in the hydraulic
brake system. Braking effort, brake pedal travel and
stopping distances may increase.
CATALYTIC CONVERTER
To prevent catalytic converter overheating, DO NOT allow
engine to idle for more than 20 minutes.
COMMAND-TRAC (4WD)
CAUTION: NEVER operate a Command-Trac vehicle in 4WD on dry,
hard-surfaced roads for a sustained period. Use 4L only
when needed for added pulling power. Operating vehicle in
4WD mode on such roads will cause stress and possible
damage to components, as well as make shifting difficult.
To reduce shifting effort, drive vehicle in Reverse for a
few feet, or drive off hard-surfaced road momentarily to
allow tire slippage.
FRONT AND REAR DIFFERENTIALS (4WD)
CAUTION: DO NOT use water, steam, kerosene or gasoline for flushing
a differential. ONLY use a flushing oil.
TRAC-LOK DIFFERENTIALS (4WD)
CAUTION: DO NOT flush a rear axle Trac-Lok differential. Trac-Lok
differentials may be cleaned only by disassembling the
unit and wiping the components with clean, lint-free cloth.
CAUTION: NEVER attempt to engage Low range when vehicle is moving
faster than 2-3 MPH, as transfer case damage may result.
GASOLINE CONTAINING ALCOHOL
CAUTION: Exclusive use of gasohol is not recommended. Vehicle test
results have shown that significant fuel system corrosion
can result when gasohol is used exclusively.