ignition MAZDA MIATA 1991 Factory Service Manual

AIR BAG RESTRAINT SYSTEM
MAZDA 1990-91 AIR BAGS
DESCRIPTION & OPERATION
The air bag restraint system, when used in conjunction with seat belt, provides increased protection for the
driver in a collision. The air bag restraint system consists of the following: AIR BAG warning light, air bag
module, clockspring connector, diagnostic module, crash sensors, back-up battery, and wiring harnesses.
The air bag is designed to deploy when rear safing sensor and at least one front impact sensor close in a
collision, and ignition switch is in the ON position. The back-up battery supplies current for the ignitor if the
vehicle battery or fuses fail during a collision. The diagnostic module monitors the air bag system for failures. I
f
any failures are detected by the module, the driver is warned of such failure(s) through the activation or flashing
of the AIR BAG warning light.
SERVICE PRECAUTIONS
Disable air bag system before servicing any air bag system or steering column component. See
DISABLING & ACTIVATING AIR BAG
SYSTEM
Wait about 10 MINUTES after disabling air bag system before servicing. Air bag system voltage is
maintained for about 10 MINUTES after system is disabled. Failure to wait 10 MINUTES before
servicing system may cause accidental air bag deployment and possible personal injury.
On Miata, obtain radio code number from customer and deactivate radio anti-theft function before
disconnecting battery.
Because of the critical system operating requirements, DO NOT service any air bag system component.
Corrections are made by replacement only.
DO NOT use an ohmmeter to check resistance of air bag module, as it may cause air bag deployment.
When carrying a live (undeployed) module, ensure trim cover is pointed away from your body. This
minimizes chance of injure in the event ofaccidental air bag deployment.
When placing a live air bag module on any surface, always face trim cover upward to reduce motion of
module if it is accidentally deployed.
If an open circuit is present, replace entire wiring harness. DO NOT attempt wire repair.
Impact sensors must always be installed with arrow marks facing front of vehicle. Also, check sensors for
cracks, defects or rust before installation. Replace impact sensor(s) if required.
Air bag system clockspring MUST be aligned in the neutral position, since its rotation ability is limited.
DO NOT turn steerin
g wheel or column after removal of steering gear. WARNING:To avoid injury from accidental air bag deployment, read and carefully
follow all WARNINGS and SERVICE PRECAUTIONS.
NOTE: The following precautions should be observed when working with air bag
systems.

1991 Mazda MX-5 Miata
AIR BAG RESTRAINT SYSTEM MAZDA 1990-91 AIR BAGS

1991 Mazda MX-5 Miata
AIR BAG RESTRAINT SYSTEM MAZDA 1990-91 AIR BAGS
Microsoft
Sunday, July 05, 2009 2:11:16 PMPage 1 © 2005 Mitchell Repair Information Company, LLC.
Microsoft
Sunday, July 05, 2009 2:11:26 PMPage 1 © 2005 Mitchell Repair Information Company, LLC.

A double-lock mechanism is used on clockspring connectors. DO NOT use excessive force when
disconnecting connectors, as damage to connector may occur.
DISABLING & ACTIVATING AIR BAG SYSTEM
AIR BAG SYSTEM
DISABLING SYSTEM
On Miata, obtain radio code number from customer, and deactivate audio anti-theft function. On all models,
turn ignition switch off. Disconnect and shield negative battery cable. Remove knee protector. Disconnect
Orange and Blue clockspring connectors at base of steering column. See Fig. 1
.
ACTIVATING SYSTEM
Reconnect battery and clockspring connectors. Turn ignition switch to RUN position. Check AIR BAG
indicator li
ght to ensure system is operating properly. See SYSTEM OPERATION CHECK. WARNING:Wait about 10 MINUTES after disabling air bag system before servicing.
Air bag system voltage is maintained for about 10 MINUTES after system
is disabled. Failure to wait 10 MINUTES before servicing system may
cause accidental air bag deployment and possible personal injury.

1991 Mazda MX-5 Miata
AIR BAG RESTRAINT SYSTEM MAZDA 1990-91 AIR BAGS
Microsoft
Sunday, July 05, 2009 2:11:16 PMPage 2 © 2005 Mitchell Repair Information Company, LLC.

Removal
1. Before proceeding, follow air bag service precautions. See SERVICE PRECAUTIONS. Disable air bag
system. See DISABLING & ACTIVATING AIR BAG SYSTEM.
2. Clockspring connector assembly is located under steering wheel, in steering column. See Fig. 4
or Fig. 5.
Remove air bag module. See AIR BAG MODULE. Remove steering wheel nut and remove steering
wheel with steering wheel puller. Remove column covers. Remove screws. Remove clockspring
connector and combination switch as an assembly.
DIAGNOSTIC MODULE & BACK-UP BATTERY
Removal & Installation
1. Before proceeding, follow air bag service precautions. See SERVICE PRECAUTIONS. Disable air bag
system. See DISABLING & ACTIVATING AIR BAG SYSTEM.
2. Diagnostic module and back-up battery is located under left side of instrument panel. See Fig. 4
or Fig.
5 . Disconnect diagnostic module and back-up battery connectors. Remove nuts. Remove diagnostic
module and back-up battery as an assembly. To install, reverse removal procedure. After diagnostic
module and back-up battery are installed, reactivate air bag system. See DISABLING & ACTIVATING
AIR BAG SYSTEM. Check AIR BAG indicator light to ensure system is functioning properly. See
SYSTEM OPERATION CHECK.
SYSTEM OPERATION CHECK
Turn ignition switch to the ON or START position. AIR BAG warning light in instrument cluster should
illuminate for approximately 6 seconds then go out. This indicates that the air bag system is functioning
properly. If any of the following conditions exists, air bag system is malfunctioning and needs repair.
AIR BAG warning light does not illuminate as described.
AIR BAG warning light stays on for more than 6 seconds.
AIR BAG warning light illuminates while driving.
If air bag system components are replaced for any reason, air bag system must be checked for proper function
after repair. Turn ignition on. AIR BAG warning light should illuminate for approximately 6 seconds then go
out. If AIR BAG warning light does not illuminate as described, air bag system is malfunctioning and needs
repair. If warning light functions as described, check horn operation. If horn does not sound, remove air bag
module and check air bag module and horn switch connections. Always follow service precautions and
deactivate air bag system before performing repairs. See DISABLING & ACTIVATING AIR BAG
SYSTEM .
WIRE REPAIR
DO NOT repair air bag system wiring. If air bag harness connectors are faulty, replace faulty wiring harness.
TORQUE SPECIFICATIONS

1991 Mazda MX-5 Miata
AIR BAG RESTRAINT SYSTEM MAZDA 1990-91 AIR BAGS
Microsoft
Sunday, July 05, 2009 2:11:16 PMPage 9 © 2005 Mitchell Repair Information Company, LLC.

cable. Turn ignition switch to ON position and check warning light operation. If warning light flashes 10
times, replace diagnostic module.
DIAGNOSTIC TEST NO. 5
Warning Light Flashes 4 Times
1. Disable air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM. Disconnect diagnostic
module Black and Gray connectors. See Fig. 10
or Fig. 11 . Check continuity between Black connector
Green/White wire terminals. If continuity is not present, replace wire harness.
2. If continuity is present, check continuity between Black connector Green wire and ground (1990 Miata),
or between Gray connector Red/Black wire terminal and ground (all others). If continuity is not present,
go to step 4). If continuity is present, check continuity between Black connector Green wire terminal and
Gray connector Green/Black wire terminal. If continuity is present, go to step 4) (1990 Miata), or step 5)
(all others).
3. If continuity is not present, disconnect rear safing sensor connectors. Check continuity between sensor
terminals "B" and "E". See Fig. 13
. If continuity is present, replace wire harness. If continuity is not
present, replace rear safing sensor.
4. Check rear safing sensor installation; repair as necessary. If installation is okay, disconnect rear safing
sensor connectors. Check continuity between sensor terminal "A" and ground. If continuity is not present,
replace rear safing sensor. If continuity is present, replace wire harness.
5. Disconnect diagnostic connector. Check continuity between Black connector Green/White wire and
ground. If continuity is present, replace wire harness. If continuity is not present, repeat step 4).

1991 Mazda MX-5 Miata
AIR BAG RESTRAINT SYSTEM MAZDA 1990-91 AIR BAGS
Microsoft
Sunday, July 05, 2009 2:11:16 PMPage 20 © 2005 Mitchell Repair Information Company, LLC.

OPERATION
Under normal driving conditions, the anti-lock brake system functions as a standard brake system. When
vehicle speed reaches 3.8 MPH, the ABS system will diagnose pump motor by briefly operating motor. Pump
motor operation may be heard inside vehicle.
The Electronic Control Unit (ECU) controls ABS by detecting speed sensor signals and activating solenoid
valve in hydraulic unit. Control unit also controls pump motor and self-diagnostic function. If a problem in the
ABS system is detected, ABS system functions as a conventional brake system. The ANTI-LOCK brake
warning light will also come on.
With detection of wheel lock-up, short pedal pulsations, occurring in rapid succession, will be felt in brake
pedal and steering wheel. Vehicle body may also vibrate slightly. These conditions are normal. Pedal pulsation
will continue until there is no longer a need for anti-lock function or until vehicle is stopped.
ANTI-LOCK BRAKE SAFETY PRECAUTIONS
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 hydraulic system without first referring to the appropriate article.
Only use specially designed brake hoses/lines on ABS-equipped vehicles.
DO NOT tap on speed sensor components (sensor, sensor rings). Speed rings must be pressed, 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 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 recommended brake fluids. DO NOT use silicone brake fluids in an ABS-equipped vehicle.
When installing transmitting 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. CAUTION: See ANTI-LOCK BRAKE SAFETY PRECAUTIONS below.
WARNING:Refer to appropriate Anti-Lock Brakes (ABS) article for description,
operation, depressurizing, testing, system bleeding, trouble shooting and
system service. Failure to depressurize ABS could lead to physical injury.

1991 Mazda MX-5 Miata
ANTI-LOCK BRAKE SYSTEM 1988-91 BRAKES Mazda Anti-Lock Brake System
Microsoft
Sunday, July 05, 2009 2:17:31 PMPage 3 © 2005 Mitchell Repair Information Company, LLC.

DO NOT expose the ABS control unit to prolonged periods of high heat (185°F/85°C for 2 hours is
generally considered a maximum limit).
BLEEDING BRAKE SYSTEM
For ABS hydraulic unit bleeding, see HYDRAULIC UNIT under REMOVAL & INSTALLATION.
BRAKE LINE BLEEDING SEQUENCE
(1)
DIAGNOSIS
ABS system can only be diagnosed using ABS Tester (0000-42-0010). See Fig. 13 . An Adapter Harness
(49N0-66-001) is also required to test Miata ABS system. ABS tester cannot diagnose ABS control unit. If a
malfunction is detected in ABS and all other components in brake system are okay, replace ABS control unit.
If ABS tester is unavailable, test each component of ABS. See test procedures under TESTING. If all ABS
components test okay, replace control unit with a known good unit, and retest system for correct operation.
PRE-DIAGNOSIS INSPECTION
Perform a visual inspection of ABS components that could cause anti-lock problem. Visual inspection may help
identify cause of simple problem.
DIAGNOSTIC PROCEDURE WITH ABS TESTER
ABS tester uses one display window and 2 switches for reading information from unit. Become thoroughly
familiar with ABS tester displays and operation before proceeding. See Fig. 13
. To diagnose ABS system, go
to TESTING SEQUENCE charts under DIAGNOSING ABS SYSTEM. When diagnosing ABS system,
complete tests in order given under TESTING SEQUENCE. If ABS tester does not operate, check fuses,
ignition switch and ignition circuit.
TESTING
NOTE: See BRAKE BLEEDING article in the BRAKES Section.
ApplicationSequence
Miata & 929Longest Line First
RX7RR, LR, RF, LF
(1)If rear caliper has not been disassembled, open upper bleed valve only.
NOTE: Before testing ABS components, ensure battery and charging system are
functioning properly. To prevent damage to ABS control unit connector, use
very thin pins when probing connector.

1991 Mazda MX-5 Miata
ANTI-LOCK BRAKE SYSTEM 1988-91 BRAKES Mazda Anti-Lock Brake System
Microsoft
Sunday, July 05, 2009 2:17:31 PMPage 4 © 2005 Mitchell Repair Information Company, LLC.

Disconnect 2-pin connector at hydraulic unit. Check continuity at hydraulic control between Red/Yellow wire
terminal and ground. If continuity is not present, replace hydraulic control unit. If continuity is present, pump is
okay. Check wiring between hydraulic control and ABS control unit.
Continuity Test (RX7 & 929)
1. Disconnect 12-pin hydraulic unit connector. Using a DVOM, check continuity between Black wire and
ground. If there is continuity, check continuity between Black wire terminal at hydraulic unit connector
and Green wire terminal at 2-pin hydraulic unit connector.
2. If continuity exists, connect hydraulic unit connectors. If continuity is not present, replace wiring harness
between control unit and body ground.
3. Disconnect ABS control unit connector. Check continuity between Green wire of ABS control unit
harness connector and ground. If continuity is present, check for poor connection of ABS control unit
connector or faulty ABS control unit. If continuity is not present, repair open circuit.
VALVE RELAY
Continuity Tests
1. Disconnect negative battery cable. Remove valve relay from hydraulic unit. Using a DVOM, check
continuity between relay terminals "C" and "E" and between terminals "B" and "D". See Fig. 11
.
2. Ensure continuity exists. Connect 12 volts to terminal "B", and ground terminal "D". Check continuity
between terminals "A" and "E". Ensure continuity exists. If continuity is not as specified, replace valve
relay.
WHEEL SPEED SENSORS
Sensor Resistance Test
Disconnect speed sensor connector. Using a DVOM, measure resistance between sensor terminals. Resistance
should be 800-1200 ohms. If resistance is not as specified, replace speed sensor.
Harness Continuity & Voltage Tests
1. With ignition off and speed sensors connected, disconnect ABS control unit connector. Using a DVOM,
check continuity between indicated terminals of ABS control unit harness connector. See WHEEL
SPEED SENSOR TESTS TABLE.
2. If reading on DVOM is not 800-1200 ohms, check wiring harness between wheel speed sensor and ABS
control unit. If DVOM reading is 800-1200 ohms, check voltage between indicated terminals in WHEEL
SPEED SENSOR TESTS TABLE.
3. Turn ignition on. Rotate appropriate wheel one revolution per second by hand to check voltage. If DVOM
does not indicate 50-60 millivolts, replace wheel speed sensor.
WHEEL SPEED SENSOR TESTS
Test Between Control Unit

1991 Mazda MX-5 Miata
ANTI-LOCK BRAKE SYSTEM 1988-91 BRAKES Mazda Anti-Lock Brake System
Microsoft
Sunday, July 05, 2009 2:17:32 PMPage 13 © 2005 Mitchell Repair Information Company, LLC.

TEST 1. CONNECTION POWER UP
CONNECTION/POWER-UP
1. Locate ABS Control Unit.
2. Disconnect Control Unit Harness from Control Unit.
3. Connect ABS Tester Harness to Control Unit Harness Connector.
4. Turn Ignition Key to "ON" position.
TEST 2 ALTERNATOR TEST
ALTERNATOR TEST START ENGINE (ALTERNATOR TESTED BY RUNNING ENGINE)
Tester will rapidly display several messages during an Initial Segment Check.
Fig. 14: Test 2 Alternator Test

Courtesy of MAZDA MOTORS CORP.
TEST 3 ABS SYSTEM TEST

1991 Mazda MX-5 Miata
ANTI-LOCK BRAKE SYSTEM 1988-91 BRAKES Mazda Anti-Lock Brake System
Microsoft
Sunday, July 05, 2009 2:17:32 PMPage 17 © 2005 Mitchell Repair Information Company, LLC.

ABS SYSTEM TEST TURN IGNITION KEY ON (DO NOT RUN ENGINE
Tester will rapidly display several messages during an Initial Segment Check.
Fig. 15: Test 3 ABS System Test

Courtesy of MAZDA MOTORS CORP.
TEST 4 SYSTEM VOLTAGE TEST

1991 Mazda MX-5 Miata
ANTI-LOCK BRAKE SYSTEM 1988-91 BRAKES Mazda Anti-Lock Brake System
Microsoft
Sunday, July 05, 2009 2:17:32 PMPage 18 © 2005 Mitchell Repair Information Company, LLC.

CHARGING SYSTEM TROUBLE SHOOTING
TROUBLE SHOOTING PRECAUTIONS
Miata
Obtain code number and deactivate audio anti-theft system before disconnecting battery.
All Models
DO NOT reverse battery cable connections. Rectifier will be damaged.
DO NOT use high voltage type testers.
PROBLEM Possible CauseAction
NO START CONDITION
Dead BatteryCheck/Replace Battery
Bad Cable ConnectionsClean/Replace Cables
Ignition Switch/Circuit FaultCheck Switch/Circuit
CHARGING SYSTEM WARNING LIGHT STAYS ON
Loose/Worn Alternator BeltTighten/Replace Belt
Loose Alternator ConnectionsCheck/Repair
Connections
Warning Light WiringCheck/Repair Wiring
Faulty Stator/DiodesTest/Repair Alternator
Faulty Voltage RegulatorTest/Repair Regulator
WARNING LIGHT OFF WITH IGNITION SWITCH ON
Blown FuseCheck/Replace Fuse
Faulty AlternatorTest Alternator
Bad Warning Light BulbTest/Replace Bulb
WARNING LIGHT ON WITH IGNITION SWITCH OFF
Alternator Wiring ShortCheck/Repair Wiring
Faulty Rectifier BridgeTest/Repair Alternator
AMMETER INDICATES DISCHARGE
Loose/Worn Alternator BeltTighten/Replace Belt
Loose Alternator ConnectionsCheck/Repair
Connections
Faulty AmmeterTest/Replace Ammeter
NOISY Defective BatteryReplace Battery
Defective AlternatorTest/Repair Alternator
Defective RegulatorTest/Repair Regulator
NOTE: Observe the following precautions when trouble shooting or testing charging
system:

1991 Mazda MX-5 Miata
ALTERNATOR & REGULATOR 1990-92 ELECTRICAL Alternators & Regulators - Mitsubishi
Microsoft
Sunday, July 05, 2009 2:14:54 PMPage 3 © 2005 Mitchell Repair Information Company, LLC.