1991 MAZDA MIATA warning

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
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Fig. 13: Identifying Rear Safing Sensor Terminals
Courtesy of MAZDA MOTORS CORP.
DIAGNOSTIC TEST NO. 6
Warning Light Flashes 6 Times
1. Disconnect negative battery cable. Check connection of Orange/Blue clockspring connector; repair as
necessary.
2. If connection is okay, disconnect air bag module and clockspring connector. Check continuity, as shown
in illustration, for both terminals of Blue side of clockspring connector. See Fig. 14
. If continuity is not
present, replace Oran
ge/Blue clockspring connector.

1991 Mazda MX-5 Miata
AIR BAG RESTRAINT SYSTEM MAZDA 1990-91 AIR BAGS
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Fig. 14: Checking Resistance at Clockspring Terminal
Courtesy of MAZDA MOTORS CORP.
3. If continuity is present, disconnect diagnostic module Black and Gray connectors. See Fig. 10
or Fig. 11.
Check continuity between diagnostic module Black connector Green/White wire and clockspring
connector Red wire. Also check continuity between diagnostic module Black connector Green/Yellow
wire and clockspring connector Green/Yellow wire. If continuity is not present, replace wire harness
assembly.
4. If continuity is present, check continuity between diagnostic module Black connector Green/Yellow wire
and ground. If continuity is present, replace wire harness assembly. If continuity is not present, replace air
bag module.
DIAGNOSTIC TEST NO. 7
Warning Light Flashes 2 Or 8 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
Brown/Yellow wire and ground. If continuity is not present, go to step 4). If continuity is present, go to
next step.

1991 Mazda MX-5 Miata
AIR BAG RESTRAINT SYSTEM MAZDA 1990-91 AIR BAGS
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Warning Light Flashes 7 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 .
2. Check continuity between Black connector Black wire and ground. If continuity is present, replace
diagnostic module. If continuity is not present, replace wire harness.
WIRING DIAGRAMS
Fig. 16: Air Bag System Wiring Diagram (1990 Miata)
Courtesy of MAZDA MOTORS CORP.

1991 Mazda MX-5 Miata
AIR BAG RESTRAINT SYSTEM MAZDA 1990-91 AIR BAGS
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ANTI-LOCK BRAKE SYSTEM
1988-91 BRAKES Mazda Anti-Lock Brake System
DESCRIPTION
The Anti-Lock Brake System (ABS) control unit senses reductions in front and rear wheel speed, and modulates
hydraulic pressure to the brakes to prevent wheel lock-up. The ABS consists of a hydraulic unit, 4 wheel speed
sensors and sensor rotors, valve relay, motor relay, pump motor, and ABS control unit. An ANTI-LOCK
warning light is located on the instrument panel. See Fig. 1
thru Fig. 3 .
Fig. 1: Locating Motor Relay & Valve Relay

Courtesy of MAZDA MOTORS CORP.

1991 Mazda MX-5 Miata
ANTI-LOCK BRAKE SYSTEM 1988-91 BRAKES Mazda Anti-Lock Brake System

1991 Mazda MX-5 Miata
ANTI-LOCK BRAKE SYSTEM 1988-91 BRAKES Mazda Anti-Lock Brake System
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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
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Fig. 7: Locating JC-02 Connector
Courtesy of MAZDA MOTORS CORP.
ANTI-LOCK WARNING LIGHT
Operational Test (Miata)
1. Start engine, and observe ANTI-LOCK light. Light should illuminate for a few seconds. If light does not
illuminate as described, remove instrument cluster. Connect 12 volts to terminal 2k of instrument cluster.
See Fig. 8
. Using a jumper wire, connect terminal 1K of instrument cluster to ground. ANTI-LOCK light
should illuminate. If light does not illuminate, check bulb. If bulb is okay, check meter fuse and wiring
harness.
2. Install instrument cluster, and recheck warning light operation. If light still does not illuminate for a few
seconds, check wiring harness between ANTI-LOCK light and control unit and between ANTI-LOCK
light and hydraulic unit. Check operation of hydraulic unit valve relay.
Operational Test (RX7)

1991 Mazda MX-5 Miata
ANTI-LOCK BRAKE SYSTEM 1988-91 BRAKES Mazda Anti-Lock Brake System
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1. Start engine, and observe ANTI-LOCK light. Light should illuminate for a few seconds. If light does not
illuminate as described, remove clock and bezel assembly from dashboard. Slide warning and clock unit
from instrument panel. Connect terminal "E" to ground. See Fig. 9
. ANTI-LOCK light should illuminate.
If light does not illuminate, check bulb. If bulb is okay, check meter fuse and wiring harness.
2. Install instrument cluster, and recheck warning light operation. If light still does not illuminate for a few
seconds, check wiring harness between ANTI-LOCK light and control unit, and ANTI-LOCK light and
hydraulic unit. Check operation of hydraulic unit valve relay.
Operational Test (929)
1. Start engine, and observe ANTI-LOCK light. Light should illuminate for a few seconds. If light does not
illuminate as described, remove instrument cluster. Connect 12 volts to terminal "J" of instrument cluster
connector I-06. See Fig. 10
. Using a jumper wire, connect terminal "E" of instrument cluster connector I-
08 to negative ground. ANTI-LOCK light should illuminate. If light does not illuminate, check bulb. If
bulb is okay, check meter fuse and wiring harness.
2. Install instrument cluster, and recheck warning light operation. If light still does not illuminate for a few
seconds, check wiring harness between ANTI-LOCK light and control unit and between ANTI-LOCK
light and hydraulic unit. Check operation of hydraulic unit valve relay.
Fig. 8: Testing ANTI
-LOCK Warning Light (Miata)
Courtesy of MAZDA MOTORS CORP.

1991 Mazda MX-5 Miata
ANTI-LOCK BRAKE SYSTEM 1988-91 BRAKES Mazda Anti-Lock Brake System
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