1991 MAZDA MIATA relay

DIAGNOSTIC TEST NO. 1
Warning Light Remains On
Disable air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM. Ensure diagnostic module
connectors are properly connected. If connector is okay, replace diagnostic module.
DIAGNOSTIC TEST NO. 2
Warning Light Flashes 3 Times
1. Measure battery voltage. If voltage is less than 9 volts, charge battery. If battery voltage is okay, check
fuses/relays in order given in FUSE/RELAY LOCATION table. See Fig. 6
or Fig. 7 .
2. If fuses and relays are okay, disable air bag system. See DISABLING & ACTIVATING AIR BAG
SYSTEM. Ensure back-up battery connector is properly connected. If connection is okay, disconnect
back-up battery connector.
Circuit (See DIAGNOSTIC TEST
NO. 2)
3Flashes 5 TimesFaulty Front Impact Sensor (See
DIAGNOSTIC TEST NO. 3)
4Flashes 10 TimesFaulty Diagnostic Module (System
Down-Fused Burned) (See
DIAGNOSTIC TEST NO. 4)
5Flashes 4 TimesFaulty Rear safing Sensor (See
DIAGNOSTIC TEST NO. 5)
6Flashes 6 TimesFaulty Air Bag Module
Poor Connection Of Clockspring
Connector (See DIAGNOSTIC
TEST NO. 6)
7 (1) Flashes 7 TimesPoor Wiring Harness Ground (See
DIAGNOSTIC TEST NO. 8)
8Flashes 8 TimesPoor Ground Of Front Impact
Sensor (See DIAGNOSTIC TEST
NO. 8)
9Flashes 9 TimesOpen Circuit Between Diagnostic
Module and Front Impact Sensor
(See DIAGNOSTIC TEST NO. 3)
10Flashes 2 TimesPoor Ground Of All Front Impact
Sensors (See DIAGNOSTIC TSET
NO. 7)
(1)Code 7 Does not apply to 1990 Miata

1991 Mazda MX-5 Miata
AIR BAG RESTRAINT SYSTEM MAZDA 1990-91 AIR BAGS
Microsoft
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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
Sunday, July 05, 2009 2:11:16 PMPage 12 © 2005 Mitchell Repair Information Company, LLC.

Fig. 6: Identifying Fuses & Relays (Miata)
Courtesy of MAZDA MOTORS CORP.

1991 Mazda MX-5 Miata
AIR BAG RESTRAINT SYSTEM MAZDA 1990-91 AIR BAGS
Microsoft
Sunday, July 05, 2009 2:11:16 PMPage 13 © 2005 Mitchell Repair Information Company, LLC.

Fig. 7: Identifying Fuses & Relays (RX7)
Courtesy of MAZDA MOTORS CORP.

1991 Mazda MX-5 Miata
AIR BAG RESTRAINT SYSTEM MAZDA 1990-91 AIR BAGS
Microsoft
Sunday, July 05, 2009 2:11:16 PMPage 14 © 2005 Mitchell Repair Information Company, LLC.

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
Sunday, July 05, 2009 2:17:31 PMPage 1 © 2005 Mitchell Repair Information Company, LLC.
Microsoft
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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
Microsoft
Sunday, July 05, 2009 2:17:31 PMPage 8 © 2005 Mitchell Repair Information Company, LLC.

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
Microsoft
Sunday, July 05, 2009 2:17:31 PMPage 9 © 2005 Mitchell Repair Information Company, LLC.

1. Disconnect hydraulic unit 12-pin connector. Using a DVOM, measure resistance between Green/Black
and Yellow/Red wires, Green/White and Yellow/Red wires and Yellow and Yellow/Red wires.
Resistance should be 1-1.2 ohms in each measurement.
2. If resistance if not as specified, replace hydraulic unit. If resistance is as specified, check wiring harness
between ABS control unit and hydraulic unit.
HYDRAULIC UNIT
Only serviceable parts of hydraulic unit are motor relay and valve relay. If other parts of unit malfunction,
replace hydraulic unit assembly.
MOTOR RELAY
Continuity Tests
1. Disconnect negative battery cable. Remove motor relay from hydraulic unit. Ensure continuity exists
between terminals "B" and "C" of motor relay. See Fig. 11
. Connect 12 volts to terminal "C", and ground
terminal "B". Ensure continuity exists between terminals "A" and "D".
2. Replace relay if continuity is not as specified. If continuity is as specified, check wiring harness between
motor relay and ABS control unit fuse (60 amps).
Fig. 11: Identifying Motor & Valve Relay Terminals

Courtesy of MAZDA MOTORS CORP.
PUMP MOTOR
Continuity Test (Miata)

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 12 © 2005 Mitchell Repair Information Company, LLC.