display 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
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electrical system overload.
BATTERY WARNING
WARNING: When battery is disconnected, vehicles equipped with
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 the COMPUTER RELEARN PROCEDURES article in GENERAL
INFORMATION section.
ELECTROSTATIC DISCHARGE SENSITIVE (ESD) PARTS
WARNING: Many solid state electrical components can be damaged by
static electricity (ESD). Some will display a warning label,
but many will not. Discharge personal static electricity by
touching a metal ground point on the vehicle prior to
servicing any ESD sensitive component.
HALOGEN BULBS
Halogen bulbs contain pressurized gas which may explode if
overheated. DO NOT touch glass portion of bulb with bare hands. Eye
protection should be worn when handling or working around halogen
bulbs.
RADIATOR CAP
CAUTION: Always disconnect the fan motor when working near the
radiator fan. The fan is temperature controlled and could
start at any time even when the ignition key is in the OFF
position. DO NOT loosen or remove radiator cap when cooling
system is hot.
Page 863 of 1378
![JEEP CHEROKEE 1988 Service User Guide with a warm engine. See the MANIFOLD AIR/FUEL TEMPERATURE (MAT) SENSOR\
RESISTANCE VALUES table below.
MANIFOLD AIR/FUEL TEMPERATURE (MAT)
SENSOR RESISTANCE VALUES
\](/img/16/57037/w960_57037-862.png "JEEP CHEROKEE 1988 Service User Guide with a warm engine. See the MANIFOLD AIR/FUEL TEMPERATURE (MAT) SENSOR\
RESISTANCE VALUES table below.
MANIFOLD AIR/FUEL TEMPERATURE (MAT)
SENSOR RESISTANCE VALUES
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with a warm engine. See the MANIFOLD AIR/FUEL TEMPERATURE (MAT) SENSOR\
RESISTANCE VALUES table below.
MANIFOLD AIR/FUEL TEMPERATURE (MAT)
SENSOR RESISTANCE VALUES
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Degrees F Degrees C Resistance (Ohms)
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-40 -40 100,700
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0 -18 25,000
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20 -7 13,500
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40 4 7,500
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70 20 3,400
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100 38 1,600
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160 70 450
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212 100 185
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3) If any resistance is not within the range as specified in
the table, replace the MAT sensor.
4) Test the resistance of the wire harness between the ECU
wire harness connector terminal "D-3" and the sensor connector
terminal "C-8".
5) Repair as necessary any circuits displaying a value
greater than one ohm.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR TEST
1) Inspect the MAP sensor vacuum hose connections at the
throttle body and the MAP sensor. See Fig. 15. Repair vacuum hose or
connections as necessary.
Fig. 15: Manifold Absolute Pressure (MAP) Sensor Connectors
Courtesy of Chrysler Motors.
2) With the ignition switch ON and engine OFF, test the MAP
sensor output voltage at the MAP sensor connector terminal "B". See
Page 864 of 1378
Fig. 15. With a hot idle condition, the voltage reading should drop to
between 0.5-1.5 volts.
3) Test ECU terminal "C-6" for the same voltage as described
in step 2) to verify the wiring harness. Repair as necessary.
4) Test the MAP sensor supply voltage at the sensor connector
terminal "C" with the ignition ON. Voltage reading should be between
4.5-5.5 volts. Check that the voltage reading at terminal "C-14" is
also 4.5-5.5 volts.
5) Repair or replace the wire harness as necessary.
6) Test the MAP sensor ground circuit at the sensor connector
terminal "A" and ECU connector terminal "D-3". Repair the wire harness
as necessary.
7) Using an ohmmeter, test the MAP sensor ground circuit at
the ECU connector between terminal "D-3" and terminal "B-ll". If an
open circuit is indicated, check for a defective sensor ground
connection. The MAP sensor ground is located on the right side of the
engine block.
8) If, after performing step 7), the ground connection is
verified to be good, check for a short to 12 volts at terminal "D-3".
If a short is found, repair the short and then replace the ECU.
KNOCK SENSOR TEST
1) Connect Diagnostic Tester M.S. 1700 to the vehicle.
2) Go to "State Display" mode.
3) Start the engine and let idle.
4) Observe knock sensor value.
5) Using the tip of a screwdriver, lightly tap the cylinder
block near the sensor while observing the knock sensor value.
6) The knock sensor value should increase when the cylinder
block is tapped.
7) If the knock sensor value does not increase while tapping
on the cylinder block near the knock sensor, check for proper
connections to the knock sensor. If connections are good, replace
the knock sensor. Refer to REMOVAL & INSTALLATION in this article.
ENGINE SPEED SENSOR TEST
1) Disconnect the engine speed sensor connector from the
ignition control module.
2) place an ohmmeter between terminals "A" and "B" (marked on\
the connector). On a hot engine, the resistance reading should be
between 125-275 ohms.
3) Replace sensor if readings are not within specification.
Fig. 16: View of Engine Speed Sensor Connectors (At Sensor)
Courtesy of Chrysler Motors.
Page 865 of 1378
SPARK PLUG CHECK
Faulty or fouled plugs may perform well at idle speed, but at
higher engine speeds, they frequently fail. Faulty plug can exhibit
the following symptoms:
* Poor fuel economy.
* Power loss.
* Decreased engine speed.
* Hard starting.
* Generally poor performance.
Spark plugs also malfunction due to carbon fouling,
excessive electrode air gap, or broken insulators.
SYNC PULSE SIGNAL GENERATOR (STATOR) TEST
NOTE: For this test, an analog voltmeter MUST be used.
1) Insert the positive (+) lead of the voltmeter into the
Blue wire at the distributor connector.
2) Insert the negative (-) voltmeter lead into the Gray/Whit\
e
wire at the distributor connector.
CAUTION: DO NOT remove the distributor connector from distributor.
Insert the voltmeter leads into the backside of the
distributor connector to make contact with the terminals.
3) Set the voltmeter to the 15-Volt D/C scale. Turn ignition
key to "ON".
4) The voltmeter should display approximately 5.0 volts.
5) If no voltage displays, check that the voltmeter leads are
making good contact. If there is still no voltage, go to next step.
6) Remove the ECU and check for voltage at pin "C-16" and
ground with harness connected. If there in still no voltage, proceed
to the next step.
7) Connect Diagnostic Tester M.S. 1700 to the vehicle. Using
the diagnostic tester, perform vehicle test. If voltage is present, go
to the next step.
8) Check for continuity between the Blue wire at the
distributor connector and pin C-16 at the ECU.
9) If there in no continuity, repair harness as necessary.
10) Check for continuity between the Gray/White wire at the
distributor connector and pin C-5 at the ECU.
11) If there is no continuity, repair harness as necessary.
12) Check for continuity between the Black wire at the
distributor connector and ground.
13) If there is no continuity, repair harness as necessary.
14) While observing the voltmeter, crank the engine; the
voltmeter needle should fluctuate back and forth while the engine in
cranking. A fluctuation verifies that the stator in the distributor is
operating properly.
15) If there is no pulse sync, replace the stator. Refer to
REMOVAL & INSTALLATION below in this article.
REMOVAL & INSTALLATION
COOLANT TEMPERATURE SENSOR (CTS)
Removal
1) Drain the cooling system.
Page 916 of 1378
ELECTROSTATIC DISCHARGE SENSITIVE (ESD) PARTS
WARNING: Many solid state electrical components can be damaged by
static electricity (ESD). Some will display a warning label,
but many will not. Discharge personal static electricity by
touching a metal ground point on the vehicle prior to
servicing any ESD sensitive component.
ENGINE OIL
CAUTION: Never use non-detergent or straight mineral oil.
CAUTION: Do not use reclaimed fluid, mineral oil, fluid that was
stored in old or open containers, or fluid inferior to AMC
Standard AM 4101. Be sure to handle the fluid in clean
containers that will not introduce even a slight amount of
foreign liquids or particles. Such contamination of fluid
could lead to hydraulic system failure.
ENGINE OIL FILTER (GASOLINE)
CAUTION: Verify that proper Oil Filter is being used. Filters with
metric threads (M20 x 1.5) must be used with some engines.
Other engines use SAE type (3/4" x 16) threads, and must
use an oil filter with these threads. Possible engine damage
can occur with improper oil filter.
ENGINE OIL FILTER (TURBO DIESEL ONLY)
CAUTION: The engine oil filter has METRIC threads. Use of a filter
with improper threads can result in oil leakage and
possible engine damage. Look for thread size symbol M20x1.5
on filter.
FUEL SYSTEM SERVICE
WARNING: DO NOT bleed fuel lines on hot engine, as high exhaust
temperatures could cause fire. Use care when bleeding fuel
lines, as fuel is under extreme pressure and could penetrate
skin, causing personal injury. Wear safety goggles and
protective clothing when bleeding fuel lines.
WARNING: Relieve fuel system pressure prior to servicing any fuel
system component.
HALOGEN BULBS
Halogen bulbs contain pressurized gas which may explode if
overheated. DO NOT touch glass portion of bulb with bare hands. Eye
protection should be worn when handling or working around halogen
bulbs.
RADIATOR CAP
CAUTION: Always disconnect the fan motor when working near the
radiator fan. The fan is temperature controlled and could
start at any time even when the ignition key is in the OFF
position. DO NOT loosen or remove radiator cap when cooling
system is hot.
STARTING FLUID USE (TURBO DIESEL)
Page 921 of 1378
MAIN TE N AN CE R EM IN DER L IG HT R ESET P R O CED URES
1988 J e ep C hero ke e
1988-92 MAINTENANCE
Chrysler Motors Maintenance Reminder Lights
Jeep; Cherokee, Comanche, Wagoneer (1988-90), Wrangler
EMISSION MAINTENANCE INDICATOR LIGHT (1988-90)
Vehicles are equipped with an emission maintenance indicator
light on instrument cluster. This light will come on one time at 82,
500 miles to alert driver that emission service is required. At this
time, oxygen sensor and PCV valve must be replaced and all other
emission components should be inspected and serviced or replaced as
necessary.
Indicator timer is located under dash, near accelerator pedal
or to right of steering column. Timer cannot be reset. To turn off
light, timer must be replaced or disconnected. Since timer and sensor
are interdependent, if timer should fail prematurely, oxygen sensor
should be replaced at same time to preserve correct replacement
interval.
To replace timer on Cherokee, Comanche and Wagoneer models,
remove cruise control module (if equipped). Remove timer mounting
screws. Disconnect electrical connector. On Wrangler models, remove
timer mounting screws. Disconnect electrical connector. On all models,
install remaining components.
EMISSION MAINTENANCE INDICATOR LIGHT (1991-92)
Vehicles are equipped with an emission maintenance indicator
light on instrument cluster. This light will come on one time at 82,
500 miles to alert driver that emission service is required. At this
time, oxygen sensor must be replaced and all other emission components
should be inspected and serviced or replaced as necessary. Chrysler's
Diagnostic Readout Box (DRB-II) tester is required to reset the
emission maintenance indicator light.
Reset Procedure
Using DRB-II tester, access SELECT SYSTEMS. Select
appropriate engine. Select with or without A/C. Select FUEL &
IGNITION. Select ADJUSTMENTS. Select RESET EMR LIGHT. Reset EMR light.
When DRB-II is finished resetting light, DRB-II display will read EMR
LIGHT IS RESET.
Page 1269 of 1378
axle backlash. If backlash is one inch or less, drive axle is not the
source of clunk noise.
Bearing Whine
Bearing whine is a high-pitched sound similar to a whistle.
It is usually caused by malfunctioning pinion bearings. Pinion
bearings operate at drive shaft speed. Roller wheel bearings may whine
in a similar manner if they run completely dry of lubricant. Bearing
noise will occur at all driving speeds. This distinguishes it from
gear whine, which usually comes and goes as speed changes.
Bearing Rumble
Bearing rumble sounds like marbles being tumbled. It is
usually caused by a malfunctioning wheel bearing. The lower pitch is
because the wheel bearing turns at only about 1/3 of drive shaft
speed.
Chatter On Turns
This is a condition where the entire front or rear of vehicle
vibrates when vehicle is moving. The vibration is plainly felt as well
as heard. Extra differential thrust washers installed during axle
repair can cause a condition of partial lock-up that creates this
chatter.
Axle Shaft Noise
Axle shaft noise is similar to gear noise and pinion bearing
whine. Axle shaft bearing noise will normally distinguish itself from
gear noise by occurring in all driving modes (Drive, cruise, coast and
float), and will persist with transmission in Neutral while vehicle is
moving at problem speed.
If vehicle displays this noise condition, remove suspect
axle shafts, replace wheel seals and install a new set of bearings.
Re-evaluate vehicle for noise before removing any internal components.
Vibration
Vibration is a high-frequency trembling, shaking or grinding
condition (felt or heard) that may be constant or variable in level
and can occur during the total operating speed range of the vehicle.
The types of vibrations that can be felt in the vehicle can
be divided into 3 main groups:
* Vibrations of various unbalanced rotating parts of the
vehicle.
* Resonance vibrations of the body and frame structures caused
by rotating of unbalanced parts.
* Tip-in moans of resonance vibrations from stressed engine or
exhaust system mounts or driveline flexing modes.
DRIVE AXLE - RWD TROUBLE SHOOTING
NOTE: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
problem symptoms. For model-specific Trouble Shooting,
refer to SUBJECT, DIAGNOSTIC, or TESTING articles available
in the section(s) you are accessing. For definitions
of listed noises or sounds, see DRIVE AXLE - NOISE DIAGNOSIS
under POWERTRAIN.
DRIVE AXLE (RWD) TROUBLE SHOOTING
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CONDITION POSSIBLE CAUSE CORRECTION
Page 1319 of 1378
full load. The Kent-Moore J-39021 is such a tool, though there are
others. The Kent-Moore costs around $240 at the time of this writing
and works on many different manufacturer's systems.
The second method is to use a lab scope. Remember, a lab
scope allows you to see the regular operation of a circuit in real
time. If an injector is having an short or intermittent short, the lab
scope will show it.
Checking Available Voltage At the Injector
Verifying a fuel injector has the proper voltage to operate
correctly is good diagnostic technique. Finding an open circuit on the
feed circuit like a broken wire or connector is an accurate check with
a DVOM. Unfortunately, finding an intermittent or excessive resistance
problem with a DVOM is unreliable.
Let's explore this drawback. Remember that a voltage drop due
to excessive resistance will only occur when a circuit is operating?
Since the injector circuit is only operating for a few milliseconds at
a time, a DVOM will only see a potential fault for a few milliseconds.
The remaining 90+% of the time the unloaded injector circuit will show
normal battery voltage.
Since DVOMs update their display roughly two to five times a
second, all measurements in between are averaged. Because a potential
voltage drop is visible for such a small amount of time, it gets
"averaged out", causing you to miss it.
Only a DVOM that has a "min-max" function that checks EVERY
MILLISECOND will catch this fault consistently (if used in that mode).\
The Fluke 87 among others has this capability.
A "min-max" DVOM with a lower frequency of checking (100
millisecond) can miss the fault because it will probably check when
the injector is not on. This is especially true with current
controlled driver circuits. The Fluke 88, among others fall into this
category.
Outside of using a Fluke 87 (or equivalent) in the 1 mS "min-\
max" mode, the only way to catch a voltage drop fault is with a lab
scope. You will be able to see a voltage drop as it happens.
One final note. It is important to be aware that an injector
circuit with a solenoid resistor will always show a voltage drop when
the circuit is energized. This is somewhat obvious and normal; it is a
designed-in voltage drop. What can be unexpected is what we already
covered--a voltage drop disappears when the circuit is unloaded. The
unloaded injector circuit will show normal battery voltage at the
injector. Remember this and do not get confused.
Checking Injector On-Time With Built-In Function
Several DVOMs have a feature that allows them to measure
injector on-time (mS pulse width). While they are accurate and fast to\
hookup, they have three limitations you should be aware of:
* They only work on voltage controlled injector drivers (e.g
"Saturated Switch"), NOT on current controlled injector
drivers (e.g. "Peak & Hold").
* A few unusual conditions can cause inaccurate readings.
* Varying engine speeds can result in inaccurate readings.
Regarding the first limitation, DVOMs need a well-defined
injector pulse in order to determine when the injector turns ON and
OFF. Voltage controlled drivers provide this because of their simple
switch-like operation. They completely close the circuit for the
entire duration of the pulse. This is easy for the DVOM to interpret.
The other type of driver, the current controlled type, start
off well by completely closing the circuit (until the injector pintle
opens), but then they throttle back the voltage/current for the
duration of the pulse. The DVOM understands the beginning of the pulse
Page 1320 of 1378
but it cannot figure out the throttling action. In other words, it
cannot distinguish the throttling from an open circuit (de-energized)
condition.
Yet current controlled injectors will still yield a
millisecond on-time reading on these DVOMs. You will find it is also
always the same, regardless of the operating conditions. This is
because it is only measuring the initial completely-closed circuit on-
time, which always takes the same amount of time (to lift the injector
pintle off its seat). So even though you get a reading, it is useless.
The second limitation is that a few erratic conditions can
cause inaccurate readings. This is because of a DVOM's slow display
rate; roughly two to five times a second. As we covered earlier,
measurements in between display updates get averaged. So conditions
like skipped injector pulses or intermittent long/short injector
pulses tend to get "averaged out", which will cause you to miss
important details.
The last limitation is that varying engine speeds can result
in inaccurate readings. This is caused by the quickly shifting
injector on-time as the engine load varies, or the RPM moves from a
state of acceleration to stabilization, or similar situations. It too
is caused by the averaging of all measurements in between DVOM display
periods. You can avoid this by checking on-time when there are no RPM
or load changes.
A lab scope allows you to overcome each one of these
limitations.
Checking Injector On-Time With Dwell Or Duty
If no tool is available to directly measure injector
millisecond on-time measurement, some techs use a simple DVOM dwell or
duty cycle functions as a replacement.
While this is an approach of last resort, it does provide
benefits. We will discuss the strengths and weaknesses in a moment,
but first we will look at how a duty cycle meter and dwell meter work.
How A Duty Cycle Meter and Dwell Meter Work
All readings are obtained by comparing how long something has
been OFF to how long it has been ON in a fixed time period. A dwell
meter and duty cycle meter actually come up with the same answers
using different scales. You can convert freely between them. See
RELATIONSHIP BETWEEN DWELL & DUTY CYCLE READINGS TABLE .
The DVOM display updates roughly one time a second, although
some DVOMs can be a little faster or slower. All measurements during
this update period are tallied inside the DVOM as ON time or OFF time,
and then the total ratio is displayed as either a percentage (duty
cycle) or degrees (dwell meter).
For example, let's say a DVOM had an update rate of exactly 1
second (1000 milliseconds). Let's also say that it has been
measuring/tallying an injector circuit that had been ON a total of 250
mS out of the 1000 mS. That is a ratio of one-quarter, which would be
displayed as 25% duty cycle or 15
dwell (six-cylinder scale). Note
that most duty cycle meters can reverse the readings by selecting the
positive or negative slope to trigger on. If this reading were
reversed, a duty cycle meter would display 75%.
Strengths of Dwell/Duty Meter
The obvious strength of a dwell/duty meter is that you can
compare injector on-time against a known-good reading. This is the
only practical way to use a dwell/duty meter, but requires you to have
known-good values to compare against.
Another strength is that you can roughly convert injector mS
on-time into dwell reading with some computations.
A final strength is that because the meter averages
everything together it does not miss anything (though this is also a