1991 MAZDA MIATA lock

3. Reconnect negative battery cable. Measure voltage between Green/Red wire of back-up battery connector
and ground. See Fig. 8
or Fig. 9 . If voltage is zero volt, replace wire harness assembly.
4. If battery voltage is present, disconnect negative battery cable and diagnostic module Black and Gray
connectors. See Fig. 10
or Fig. 11 . Reconnect negative battery cable. Measure voltage between
White/Green wire of Gray diagnostic module connector and ground. If voltage is zero volt, replace wire
harness assembly.
5. If battery voltage is present, measure voltage between Green/Yellow wire of Gray diagnostic module
connector and ground. If voltage is zero volt, replace wire harness assembly. If battery voltage is present,
replace diagnostic module.
FUSE/RELAY LOCATION
Fuse/RelayLocation
Miata
Air Bag (15 Amps)In Fuse Block
Air Bag (10 Amps)In Main Fuse Block
Engine (15 Amps)In Fuse Block
INJ (30 Amps)In Main Fuse Block
RX7
Air Bag (15 Amps)In Fuse Block
Air Bag (30 Amps)In Main Fuse Block
Engine (30 Amps)In Main Fuse Block
Wiper (15 Amps)In Fuse Block

1991 Mazda MX-5 Miata
AIR BAG RESTRAINT SYSTEM MAZDA 1990-91 AIR BAGS
Microsoft
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Fig. 12: Checking Impact Sensor Resistance
Courtesy of MAZDA MOTORS CORP.
DIAGNOSTIC TEST NO. 4
Warning Light Flashes 10 Times
1. Disable air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM. Disconnect front
impact sensor connectors (center, left, and right), and measure resistance of each sensor. See Fig. 12
.
Resistance should be approximately 1.2 k/ohms. If resistance is not as specified, replace sensor and go to
step 5).
2. If resistance is about 1.2 k/ohms, reconnect all front impact sensor connectors. Disconnect diagnostic
module Black and Gray connectors. See Fig. 10
or Fig. 11 . Measure resistance between diagnostic
module Gray connector Brown/Green wire and ground. If resistance is 1.2 k/ohms, go to next step. If
resistance is not 1.2 k/ohms, replace wire harness.
3. Measure resistance between diagnostic module Gray connector Brown/Red wire and ground. If resistance
is 1.2 k/ohms, go to next step. If resistance is not 1.2 k/ohms, replace wire harness.
4. Measure resistance between diagnostic module Black connector Brown/Black wire and ground. If
resistance is 1.2 k/ohms, go to next step. If resistance is not 1.2 k/ohms, replace wire harness and go to
next step.
5. If disconnected, reconnect dia
gnostic module and clockspring connectors. Reconnect negative battery

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
Microsoft
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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
Microsoft
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Fig. 2: Locating ABS Components (RX7 Shown; Miata Similar)
Courtesy of MAZDA MOTORS CORP.
Fig. 3: Locating ABS Components (929)

Courtesy of MAZDA MOTORS CORP.
NOTE: For more information on brake system, see BRAKE SYSTEM article in the
BRAKES Section.

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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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
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