signal MITSUBISHI MONTERO 1991 Service Manual

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AN TI- L O CK B RAK E S A FE TY P R EC AU TIO NS

1991 M it s u bis h i M onte ro
GENERAL INFORMATION
Anti-Lock Brake Safety Precautions
* PLEASE READ THIS FIRST *
This article is intended for general information purposes
only. This information may not apply to all makes and models. If
vehicle is equipped with Anti-Lock Brake System (ABS), refer to
appropriate ANTI-LOCK BRAKE SYSTEM article in the BRAKES section for
description, operation, depressurizing, testing, system bleeding,
trouble shooting and servicing of specific system.
WARNING: Failure to depressurize ABS could lead to physical injury.
ANTI-LOCK BRAKE SAFETY PRECAUTIONS
WARNING: Failure to depressurize ABS could lead to physical injury.
* NEVER open a bleeder valve or loosen a hydraulic line
while ABS is pressurized.
* NEVER disconnect or reconnect any electrical connectors
while ignition is on. Damage to ABS control unit may result.
* DO NOT attempt to bleed hyudarulic system without first
referring to the appropriate ANTI-LOCK BRAKE SYSTEM article
in the BRAKES section.
* Only use specially designed brake hoses/lines on ABS equipped
vehicles.
* DO NOT tap on speed sensor components (sensor, sensor rings).
Sensor rings must be pressed into hubs, NOT hammered into
hubs. Striking these components can cause demagnetization or
a loss of polarization, affecting the accuracy of the speed
signal returning to the ABS control unit.
* DO NOT mix tire sizes. Increasing the width, as long as tires
remain close to the original diameter, is acceptable. Rolling
diameter must be identical for all 4 tires. Some
manufacturers recommend tires of the same brand, style and
type. Failure to follow this precaution may cause inaccurate
wheel speed readings.
* DO NOT contaminate speed sensor components with grease. Only
use recommended coating, when system calls for an
anti-corrosion coating.
* When speed sensor components have been removed, ALWAYS check
sensor-to-ring air gaps when applicable. These specifications
can be found in each appropriate article.
* ONLY use rocommended brake fluids. DO NOT use silicone brake
fluids in an ABS equipped vehicle.
* When instlling transmittion devices (CB's, telephones, etc.)
on ABS equipped vehicles, DO NOT locate the antenna near the
ABS control unit (or any control unit).
* Disconnect all on-board computers, when using electric
welding equipment.
* DO NOT expose the ABS control unit to prolonged periods of
high heat (185
F/85C for 2 hours is generally considered a
maximum limit).

and make an informed decision about how to proceed.
BRAKES
SERVICE PROCEDURES REQUIRED & SUGGESTED FOR PROPER
VEHICLE OPERATION
Some states may have specifications that differ from OEM.
Check your local/state regulations. Where state or local laws are
stricter, they take precedence over these guidelines.
ACCELEROMETERS (G SENSOR OR LATERAL)
ACCELEROMETER INSPECTION








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Condition Code Procedure
Broken .................. A ............ Require replacement.
Connector loose ......... A .. Require repair or replacement.
Loose ................... B .. Require repair or replacement.
Missing ................. C ............ Require replacement.
Out of position ......... B ....... Require re-positioning to
vehicle manufacturer's
specifications.
Output signal incorrect . B ............ Require replacement.









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ACCUMULATORS
ACCUMULATOR INSPECTION








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Condition Code Procedure
Leaking ................. B ............ Require replacement.
Missing ................. C ............ Require replacement.
Pre-charge incorrect .... B ............ Require replacement.









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ANCHOR PINS
See BACKING PLATES .
ANTI-LOCK BRAKE SYSTEMS
NOTE: Anti-lock brakes are an integral part of the brake system. It
is essential that the anti-lock brakes function properly when
brake service is performed.
Anti-lock brake systems are commonly referred to as "ABS" and
will be referred to as "ABS" throughout these guidelines. Some ABS
components also function as part of a traction control system (TCS).
WARNING: When diagnosing and servicing high pressure components,
observe safety procedures and equipment requirements
established by the vehicle manufacturer to reduce the
possibility of serious personal injury.
NOTE: Intermittent electrical conditions are often caused by a loss
of ground, poor connection, or water intrusion into the
wiring harness.

Connector melted ........ A ........ (1) Require replacement.
Connector missing ....... C ............ Require replacement.
Missing ................. C ............ Require replacement.
Out of adjustment ....... B ........... Require adjustment or
replacement.
Output signal incorrect . B ............ Require replacement.
Terminal burned, affecting
performance ............ A .............. ( 2) Require repair
or replacement.
Terminal burned, not
affecting performance .. 2 .. Suggest repair or replacement.
Terminal corroded,
affecting performance ... A .. Require repair or replacement.
Terminal corroded, not
affecting performance ... 2 .. Suggest repair or replacement.
Terminal loose, affecting
performance ............ B .. Require repair or replacement.
Terminal loose, not
affecting performance ... 1 .. Suggest repair or replacement.
Threads damaged ......... A .. Require repair or replacement.
Threads stripped (threads
missing) ............... A ............ Require replacement.
( 1) - Determine cause and correct prior to replacement of part.
( 2) - Determine cause and correct prior to repair or replacement
of part.









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BULB SOCKETS
BULB SOCKET INSPECTION








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Condition Code Procedure
Attaching hardware
broken ................. A ... Require repair or replacement
of hardware.
Attaching hardware
missing ................ C .......... Require replacement of
hardware.
Attaching hardware not
functioning ............ A ... Require repair or replacement
of hardware.
Broken .................. A .. Require repair or replacement.
Bulb seized in socket ... A .. Require repair or replacement.
Burned, affecting
performance ............ A .............. ( 1) Require repair
or replacement.
Burned, not affecting
performance ............ 2 .............. ( 1) Suggest repair
or replacement.
Connector broken ........ A .. Require repair or replacement.
Connector missing ....... C ............ Require replacement.
Connector (Weatherpack
type) leaking .......... A .. Require repair or replacement.
Connector melted ........ A .............. ( 2) Require repair
or replacement.
Corroded, affecting
performance ............ A .. Require repair or replacement.
Corroded, not affecting
performance ............ 2 .. Suggest repair or replacement.
Leaking ................. A .. Require repair or replacement.
Melted .................. A ........ ( 2) Require replacement.

of caliper.
Piston sticking ......... A ........... Require rebuilding or
replacement of caliper.
Slide mechanism
sticking ............... A ... Require repair or replacement
of slide mechanism.
(1) - Only required if the hydraulic system must be opened.
( 2) - Seized is defined as a bleeder screw that cannot be
removed after a practical attempt at removing. Only
required if the hydraulic system must be opened.









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CONTROLLERS
See ELECTRONIC CONTROLLERS .
DIGITAL RATIO AXLE CONTROLLERS AND BUFFERS (DRAC AND DRAB)
DIGITAL RATIO AXLE CONTROLLER AND BUFFER INSPECTION








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Condition Code Procedure
Connector broken ........ A .. Require repair or replacement.
Connector (Weatherpack
type) leaking .......... A .. Require repair or replacement.
Connector melted ........ A ........ ( 1) Require replacement.
Connector missing ....... C ............ Require replacement.
Missing ................. C ............ Require replacement.
Output signal incorrect . B .. Require repair or replacement.
Terminal burned, affecting
performance ............ A .............. ( 2) Require repair
or replacement.
Terminal burned, not
affecting performance .. 2 .. Suggest repair or replacement.
Terminal corroded,
affecting performance .. A .. Require repair or replacement.
Terminal corroded, not
affecting performance .. 2 .. Suggest repair or replacement.
Terminal loose, affecting
performance ............ B .. Require repair or replacement.
Terminal loose, not
affecting performance .. 1 .. Suggest repair or replacement.
( 1) - Determine cause and correct prior to replacement of part.
( 2) - Determine cause and correct prior to repair or
replacement of part.









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DISABLE SWITCHES
See SWITCHES.
DRUMS
Determine the need to recondition based upon individual drum
conditions that follow. Friction material replacement does not require
drum reconditioning unless other justifications exist. DO NOT
recondition new drums unless they are being pressed or bolted onto an
existing hub. It is not necessary to replace drums in axle sets.
However, when replacing or reconditioning a drum due to the conditions
that follow, you may suggest reconditioning of the other drum on the

Seat Belt Warning Timer Behind left side of dash.
Sun Roof Control Relay In headliner, near dome light
bracket.
Turn Signal Flasher Relay Behind left side of dash.








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CIRCUIT PROTECTION DEVICES

CRUISE CONTROL VACUUM HOSES, TUBES AND RESERVOIRS
CRUISE CONTROL VACUUM HOSE, TUBE AND RESERVOIR INSPECTION








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Condition Code Procedure
Leaking ................. A .. Require repair or replacement.
Melted .................. A ............ Require replacement.
Missing ................. C ............ Require replacement.
Oil-soaked (spongy) ..... 1 ............ Suggest replacement.
Restricted .............. A .. Require repair or replacement.
Surface cracks (dry-
rotted) ................ 1 ............ Suggest replacement.









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CRUISE CONTROL VEHICLE SPEED SENSORS
CRUISE CONTROL VEHICLE SPEED SENSOR INSPECTION








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Condition Code Procedure
Air gap incorrect ....... B ....... ( 1) Require adjustment to
vehicle manufacturer's
specifications.
Attaching hardware
broken ................. A ... Require repair or replacement
of hardware.
Attaching hardware
missing ................ C .......... Require replacement of
hardware.
Attaching hardware not
functioning ............ A ... Require repair or replacement
of hardware.
Broken .................. A ............ Require replacement.
Housing cracked ......... A ............ Require replacement.
Internal resistance
does not meet
specifications ......... B ........ ( 2) Require replacement.
Lead routing incorrect .. B .. Require rerouting according to
vehicle manufacturer's
specifications.
Loose ................... B ....... ( 3) Require adjustment to
vehicle manufacturer's
specifications.
Missing ................. C ............ Require replacement.
Output signal incorrect . B ........... ( 2) Require repair or
replacement.
Surface contaminated .... 2 .. Suggest cleaning; identify and
correct source.
Tip bent ................ B ............ Require replacement.
Tip broken .............. B ............ Require replacement.
Tip missing ............. B ............ Require replacement.
Wire lead burned ........ A ............ Require replacement.
Wire lead conductors
exposed ................ B ............ Require replacement.
Wire lead corroded ...... A ............ Require replacement.
Wire lead open .......... A ............ Require replacement.
Wire lead shorted ....... A ............ Require replacement.
( 1) - If a sensor is not adjustable, further inspection is
required to identify and correct cause.
( 2) - Component failure may be caused by water intrusion into
the wiring harness. Always check insulation for damage

Single Diaphragm EGR Valve
This type uses a single diaphragm connected to the valve by a
shaft. Diaphragm is spring-loaded to keep valve closed in the absence
of vacuum. As throttle valves open and engine speed increases, vacuum
is applied to the EGR vacuum diaphragm, opening the EGR valve. This
vacuum signal comes from a ported vacuum source. Variations in the
vacuum signal control the amount of exhaust gas that is recirculated.
See Fig. 7 .
Verify EGR valve is present and not modified or purposely
damaged. Ensure thermal vacuum switches, pressure transducers, speed
switches, etc., (if applicable) are not by-passed or modified. Ensure
vacuum hose(s) to EGR valve is not plugged.
Fig. 7: Typical Single Diaphragm EGR Valve
Courtesy of General Motors Corp.
Dual Diaphragm EGR Valve
This type uses 2 diaphragms with different effective areas
and 2 vacuum sources. Although similar to the single diaphragm type,
the second diaphragm is added below the upper diaphragm and is rigidly
attached to the valve seat. See Fig. 8. These diaphragms form a vacuum
chamber which is connected to manifold vacuum.
During highway cruising when manifold vacuum is high in the
center chamber, manifold vacuum tends to pull the valve closed.
However, the vacuum signal applied to the top side of the upper
diaphragm overcomes the downward spring force and the manifold vacuum
pull, due to the diaphragm's larger piston. This regulates the amount
of EGR.
When manifold vacuum is low during acceleration, the higher
vacuum signal opens the valve, permitting more EGR. When manifold
vacuum is high during highway cruising, the valve is only partially
opened, reducing the amount of EGR.

Verify EGR valve is present and not modified or purposely
damaged. Ensure thermal vacuum switches, pressure transducers, speed
switches, etc., (if applicable) are not by-passed or modified. Ensure
vacuum hose(s) to EGR valve is not plugged.
Fig. 8: Typical Dual Diaphragm EGR Valve
Courtesy of General Motors Corp.
Positive Backpressure EGR (BP/EGR) Valve
This type uses both engine vacuum and exhaust backpressure to
control the amount of EGR. It provides more recirculation during heavy
engine loads than the single diaphragm EGR valve.
A small diaphragm-controlled valve inside EGR valve acts as a
pressure regulator. The control valve gets an exhaust backpressure
signal through the hollow valve shaft. This exhaust backpressure
exerts a force on bottom of control valve diaphragm. The diaphragm
plate contains 6 bleed holes to bleed air into the vacuum chamber when
backpressure valve is in open position. See Fig. 9.
Verify EGR valve is present and not modified or purposely
damaged. Ensure thermal vacuum switches, pressure transducers, speed

switches, etc., (if applicable) are not by-passed or modified. Ensure
vacuum hose(s) to EGR valve is not plugged.
Fig. 9: Typical Positive Backpressure EGR Valve
Courtesy of General Motors Corp.
Negative Backpressure EGR (BP/EGR) Valve
This type has the same function as the positive BP/EGR valve
except valve is designed to open with a negative exhaust backpressure.
The control valve spring in the transducer is placed on the bottom
side of the diaphragm. See Fig. 10.
When ported vacuum is applied to the main vacuum chamber,
partially opening the valve, the vacuum signal from the manifold side
(reduced by exhaust backpressure) is transmitted to the hollow stem of\
the valve. See Fig. 10. This enables the signal to act on the
diaphragm, providing a specific flow. Thus, the EGR flow is a constant
percentage of engine airflow.
Verify EGR valve is present and not modified or purposely
damaged. Ensure thermal vacuum switches, pressure transducers, speed
switches, etc., (if applicable) are not by-passed or modified. Ensure
vacuum hose(s) to EGR valve is not plugged.

remote vacuum regulator. The internal solenoid is normally open, which
causes the vacuum signal to be vented off to the atmosphere when EGR
is not controlled by the Electronic Control Module (ECM). The solenoid\
valve opens and closes the vacuum signal, controlling the amount of
vacuum applied to the diaphragm. See Fig. 12.
The electronic EGR valve contains a voltage regulator, which
converts ECM signal and regulates current to the solenoid. The ECM
controls EGR flow with a pulse width modulated signal based on
airflow, TPS and RPM. This system also contains a pintle position
sensor, which works similarly to a TPS sensor. As EGR flow is
increased, the sensor output increases.
Verify EGR valve is present and not modified or purposely
damaged. Ensure thermal vacuum switches, pressure transducers, speed
switches, etc., (if applicable) are not by-passed or modified. Ensure
electrical connector to EGR valve is not disconnected.
Fig. 12: Cutaway View Of Typical Integrated Electronic EGR Valve
Courtesy of General Motors Corp.
SPARK CONTROLS (SPK)