Engine control MAZDA MX-5 1997 Factory User Guide

5. Reconnect all harness connectors. Road test vehicle. Retrieve DTC. If code P0715 is still present, replace
PCM. If code is no longer present, system is okay.
DTC P0725: ENGINE SPEED INPUT CIRCUIT MALFUNCTION
Condition
Engine speed input signal is not input to TCM. Possible causes are:
Crankshaft position sensor malfunction.
Damaged wiring or connectors between ECM and TCM.
ECM malfunction.
TCM malfunction.
Diagnosis & Repair Procedure
1. Ensure all connections are clean and tight. Repair as needed. Turn ignition on. Using voltmeter,
backprobe TCM harness connector. DO NOT disconnect connector.
2. Measure voltage between ground and terminal No. 1N (White wire) on TCM harness connector. Voltage
should be zero or 4.5-5.5 volts with engine stopped or 2-3 volts with engine idling. If voltage is within
specifications, go to step 7 . If voltage is not within specifications, go to next step.
3. Ignition off. Measure continuity between terminal No. 1N (White wire) on TCM harness connector and
terminal No. 4F (White wire) on ECM harness connector. If continuity is not present, repair wiring then
go to step 7 .
4. Using voltmeter, backprobe ECM harness connector. Measure voltage between ground and terminal No.
4H (Yellow/White wire). Voltage should be less than one volt with engine stopped or greater than one
volt with engine idling. If voltage is within specifications, go to step 7 . If voltage is not within
specifications, go to next step.
5. Inspect crankshaft position sensor. See appropriate SYSTEM & COMPONENT TESTS article in
ENGINE PERFORMANCE. Replace as needed. If sensor is okay, go to next step.
6. Turn ignition off. Using ohmmeter, backprobe TCM harness connector. DO NOT disconnect connector.
Measure resistance between terminals 1N (White wire) and 2P (Black/Light Green wire). If resistance is
7.2-8.0 ohms, go to next step. If resistance is not 7.2-8.0 ohms, replace TCM.
7. Reconnect all harness connectors. Road test vehicle. Retrieve DTC. If code P0725 is still present, replace
TCM. If code is no longer present, problem is intermittent.
DTC P0731: INCORRECT 1ST GEAR RATIO NOTE: If DTC P0335 is also present, repair it first and then proceed with this test. Go to
appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE and
perform test.
NOTE: If any following DTC is also present, repair it first and then proceed with this
test: DTC P0750
, P0755 , P0760 .

1997 Mazda MX-5 Miata
1997 AUTOMATIC TRANSMISSIONS NC4A-EL Electronic Controls
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1. Inspect ATF level and condition. Correct as needed. If fluid level and condition is okay, check line
pressure. See LINE PRESSURE TEST under TESTING in MAZDA NC4A-EL OVERHAUL article.
Follow repair recommendations if line pressure is not within specifications. If line pressure is okay, go to
next step.
2. Inspect lock-up solenoid. See SOLENOID VALVES
under COMPONENT TESTING. Repair as
needed. If solenoid valve is okay, go to next step.
3. Inspect lock-up control valve in valve body. If valve is okay, go to next step.
4. Using an EC-AT tester connected to TCM, ensure that engine speed and turbine speed during TCC lock-
up in 4th gear are the same. If speeds are different, replace torque converter. If speeds are the same, go to
next step.
5. Clear DTC. See CLEARING CODES
. Retrieve DTC. If DTC P0740 is still present, replace TCM. If
code is no longer present and symptom still exists, problem may be caused by intermittent TCC slippage.
Further investigation may be required. See MAZDA NC4A-EL OVERHAUL article.
DTC P0750: 1-2 SHIFT SOLENOID MALFUNCTION
Possible Causes:
Short or open circuit between TCM and solenoid.
TCM malfunction.
Shift solenoid malfunction.
Diagnosis & Repair Procedure
1. Ensure all connections are clean and tight. Repair as needed. Turn ignition on. Access TCM connectors.
Using voltmeter, backprobe harness connectors. DO NOT disconnect connectors. Go to next step.
2. Measure voltage between ground and terminal No. 2E (Blue/Yellow wire) on TCM connector. During
test drive, voltage should be less than one volt when solenoid is off and battery voltage when solenoid is
on. See SOLENOID OPERATION
table under TCM OUTPUT DEVICES. If voltage is within
specification, go to step 5 . If voltage is not within specification, go to next step.
3. Turn ignition off. Disconnect TCM harness connector. Measure resistance between ground and terminal
No. 2E. If resistance is 13-27 ohms at 68°F (20°C), go to step 5 . If resistance is not 13-27 ohms at 68°F
(20°C), go to next step.
4. Inspect 1-2 shift solenoid and related circuits. See SOLENOID VALVES
under COMPONENT
TESTING. Repair as needed. If solenoid valve and related circuits are okay, go to next step.
5. Clear DTC and road test vehicle. Retrieve DTC. If DTC P0750 is still present, replace TCM. If code is no
longer present, system is okay.
DTC P0755: 2-3 SHIFT SOLENOID MALFUNCTION
Possible Causes:
Short or open circuit between TCM and solenoid.
TCM malfunction.

1997 Mazda MX-5 Miata
1997 AUTOMATIC TRANSMISSIONS NC4A-EL Electronic Controls
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1. Ensure all connections are clean and tight. Repair as needed. Ensure that TP sensor is adjusted correctly.
See appropriate ON-VEHICLE ADJUSTMENTS article in ENGINE PERFORMANCE. Turn ignition
on. Access TCM connectors. Using voltmeter, backprobe harness connectors. DO NOT disconnect
connectors. Go to next step.
2. Measure voltage between ground and terminal No. 2T (Red/Black wire) on TCM harness connector. With
throttle closed, voltage should be .1-1.1 volts. With wide open throttle, voltage should be 3.1-4.4 volts. If
voltage is within specification, go to step 5 . If voltage is not within specification, go to next step.
3. Measure voltage between ground and terminal No. 2A (Light Green/White wire) on TCM harness
connector. With ignition on, voltage should be 4.5-5.5 volts. With ignition off, voltage should be zero
volts. If voltage is within specification, go to step 5 . If voltage is not within specification, go to next step.
4. Inspect circuits between TP sensor and TCM. See appropriate wiring diagram under WIRING
DIAGRAMS . Repair as needed. If circuits are okay between sensor and TCM, go to next step.
5. Clear codes, and road test vehicle. Retrieve DTC. If DTC P1790 is still present, replace TCM. If code is
no longer present, system is okay.
DTC P1795: IDLE SWITCH OPEN OR SHORT
Condition
Closed throttle position switch is ON and TP sensor position is closed. Possible causes are:
Damaged wiring or connectors between closed throttle position switch and TCM.
Closed throttle position switch malfunction.
TCM malfunction.
Diagnosis & Repair Procedure
1. Ensure all connections are clean and tight. Repair as needed. Turn ignition on. Access TCM connectors.
Using voltmeter, backprobe harness connectors. DO NOT disconnect connectors. Go to next step.
2. Measure voltage between ground and terminal No. 1O (Red wire) on TCM harness connector. With
throttle closed, battery voltage should be present. With wide open throttle, voltage should be zero volts. If
voltage is within specification, go to step 5 . If voltage is not within specification, go to next step.
3. Inspect circuits between closed throttle position switch and TCM. See appropriate wiring diagram under
WIRING DIAGRAMS
. Repair as needed. If circuits are okay between sensor and TCM, go to next
step.
4. Disconnect battery negative cable. Disconnect closed throttle position switch connector. Check for
continuity between closed throttle position switch terminals. If continuity exists, go to next step. If
continuity does not exist, replace or adjust throttle position sensor.
5. Clear codes, and road test vehicle. Retrieve DTC. If DTC P1795 is still present, replace TCM. If code is
no longer present, problem is intermittent. Further investigation is required.
COMPONENT TESTING
NOTE: For connector terminal identification, see COMPONENT CONNECTOR

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1997 AUTOMATIC TRANSMISSIONS NC4A-EL Electronic Controls
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GENERAL INFORMATION
Computer Relearn Procedures
COMPUTER RELEARN PROCEDURES
Vehicles equipped with engine or transmission computers may require a relearn procedure after vehicle battery
is disconnected. Many vehicle computers memorize and store vehicle operation patterns for optimum
driveability and performance. When vehicle battery is disconnected, this memory is lost. The computer will use
default data until new data from each key start is stored. As computer memorizes vehicle operation for each
new key start, driveability is restored. Vehicle computers may memorize vehicles operation patterns for 40 of
more key starts.
Customers often complain of driveability problems during relearn stage because vehicle acts differently then
before being serviced. Depending on type and make of vehicle and how it is equipped, the following complaints
(driveability problems) may exist:
Harsh Or Poor Shift Quality
Rough Or Unstable Idle
Hesitation Or Stumble
Rich Or Lean Running
Poor Fuel Mileage
These symptoms and complaints should disappear after a number of drive cycles have been memorized. To
reduce the possibility of complaints, after any service which requires battery power to be disconnected, vehicle
should be road tested.
GENERIC COMPUTER RELEARN PROCEDURES
Some manufacturers identify a specific relearn procedure which will help establish suitable driveability during
relearn stage. These procedures are especially important if vehicle is equipped with and electronically
controlled automatic transmission or transaxle. Always complete procedure before returning vehicle to
customer. The following general procedures are to be used if driveability problems are encountered after power
loss or battery has been disconnected. These procedures may provide an aid in eliminating these problems.
Automatic Transmission
Set parking brake, start engine in "P" or "N" position. Warm-up vehicle to normal operating temperature
or until cooling fan cycles.
Allow vehicle to idle for one minute in "N" position. Select "D" and allow engine to idle for one minute.
Accelerate at normal throttle position (20-50%) until vehicle shifts into top gear.
Cruise at light to medium throttle.
Decelerate to a stop, allowing vehicle to downshift, and use brakes normally.
Process may be repeated as necessary.

1997 Mazda MX-5 Miata
GENERAL INFORMATION Computer Relearn Procedures

1997 Mazda MX-5 Miata
GENERAL INFORMATION Computer Relearn Procedures
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Fig. 5: Exploded View Of Rear Axle Shaft (MPV)
Courtesy of MAZDA MOTORS CORP.
DIFFERENTIAL ASSEMBLY
Removal (Front MPV 4WD)
1. Raise and support vehicle. Remove engine skid plate. See Fig. 6 . Drain front differential fluid. Remove
tie rod ends and lower control arms. Remove front axle shafts. See AXLE SHAFTS
- FRONT article.
2. Mark drive shaft and differential carrier flanges for reassembly reference, and remove drive shaft from
differential carrier. See Fig. 6
. Disconnect Automatic Free Wheel (AFW) vacuum hoses and electrical
connector.
3. Place floor jack under differential assembly. Remove differential-to-chassis mounting bolts and AFW
extension housing mounting nuts. Remove differential and AFW extension housing from vehicle.
Remove AFW assembly from left side of differential housing. Pull drive coupler from carrier. Remove
differential carrier-to-housing bolts. Remove differential carrier.
Installation
To install, reverse removal procedure. Apply sealant to carrier mating flange. Align marks made during
removal. Refill differential with lubricant. Tighten all nuts and bolts to specification. See TORQUE
SPECIFICATIONS.

1997 Mazda MX-5 Miata
1997-98 DRIVE AXLES Differentials & Drive Axles - MPV & MX-5 Miata
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1997 MAZDA
MX-5 Miata
BUZZERS, RELAYS & TIMERS
BUZZERS, RELAYS & TIMERS
CIRCUIT PROTECTION DEVICES
CIRCUIT PROTECTION DEVICES
CONTROL UNITS
CONTROL UNITS
ComponentComponent Location
A/C RelayIn right front of engine compartment, near radiator. See Fig. 1 .
Condenser Fan RelayIn right front of engine compartment, near radiator. See Fig. 1 .
Cooling Fan RelayIn main fuse/relay block.
Flasher UnitBehind left side of dash. See Fig. 2 .
Fuel Pump RelayUnder left side of dash. See Fig. 2 .
Headlamp RelayOn left rear corner of front inner fender panel. See Fig. 1 .
Horn RelayOn left rear corner of front inner fender panel. See Fig. 1 .
INT RelayIntegral with windshield wiper & washer switch.
Main RelayIn left rear corner of engine compartment, in main fuse/relay block.
Power Antenna RelayIn right rear of vehicle, attached to power antenna.
Rear Window Defogger
RelayIn center rear of trunk compartment. See Fig. 3 .
Retractable Headlamp RelayBehind left side of dash.
TNS RelayIn left rear corner of engine compartment, on inner fender panel. See Fig.
1 .
Warning UnitBehind left side of dash. See Fig. 2 .
ComponentComponent Location
Fuse Block (Front)Behind left side of dash. See Fig. 2 .
Fuse Block (Rear)On right rear side of luggage compartment. See Fig. 3 .
Main Fuse BlockOn right rear corner of engine compartment, near firewall. See Fig. 1 .
ComponentComponent Location
ABS Control ModuleBehind passenger's seat. See Fig. 3 .
ABS Control UnitIn right rear corner of engine compartment.
Cruise Control ModuleUnder left side of dash above fuse block. See Fig. 2 .
Daytime Running Lamp (DRL) Control ModuleOn bracket, behind left side of dash. See Fig. 2 .
Engine Control Module (ECM)Behind passenger's seat. See Fig. 3 .

1997 Mazda MX-5 Miata
1997 MAZDA MX-5 Miata

1997 Mazda MX-5 Miata
1997 MAZDA MX-5 Miata
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MOTORS
MOTORS
SENDING UNITS & SENSORS
SENDING UNITS & SENSORS
Key Interlock UnitBehind left side of dash. See Fig. 2 .
SAS UnitBehind center of dash. See Fig. 2 .
Transmission Control Module (TCM)Under left side of dash, near fuse block. See Fig. 2 .
ComponentComponent Location
Blower MotorUnder right side of dash. See Fig. 2 .
Condenser Fan MotorIn front of engine compartment.
Cooling Fan MotorIn front of engine compartment.
Cruise Control ActuatorOn left side of engine compartment.
Fuel PumpIn fuel tank.
Power Antenna MotorIn right front of trunk.
Retractable Headlamp ActuatorsBehind respective headlamp.
Shift Lock ActuatorUnder center console, on base of gear selector.
Windshield Washer MotorOn bottom of washer fluid reservoir.
Windshield Wiper MotorOn right side of firewall.
ComponentComponent Location
ABS Wheel Speed Sensor (Left Front)On back of left front wheel spindle assembly. See Fig. 1 .
ABS Wheel Speed Sensor (Left Rear)On back of left rear wheel hub assembly. See Fig. 3 .
ABS Wheel Speed Sensor (Right Front)On back of right front wheel spindle assembly. See Fig. 1 .
ABS Wheel Speed Sensor (Right Rear)On back of right rear wheel hub assembly. See Fig. 3 .
Brake Fluid Level SensorIn brake fluid reservoir. See Fig. 1 .
Camshaft Position SensorIn center rear of engine compartment. See Fig. 1 .
Crankshaft Position SensorOn front of engine.
EGR Boost SensorOn right side of engine compartment.
EGR Valve Position SensorOn right side center, rear of engine compartment.
EGR Valve Position SensorOn right side center, rear of engine compartment. See Fig. 1 .
Engine Coolant Temperature SensorOn rear of engine. See Fig. 1 .
Fuel Gauge Sender UnitIn fuel tank.
Heated Oxygen Sensor (Front)In rear of engine compartment. See Fig. 1 .
Heated Oxygen Sensor (Rear)On underside of vehicle, on exhaust pipe.
Input/Turbine Speed SensorOn left side of transmission.
Mass Air Flow SensorOn top of air filter housing. See Fig. 1 .
Throttle Position (TP) SensorOn side of throttle body. See Fig. 1 .
Transmission Fluid Temperature SensorOn left side of transmission.

1997 Mazda MX-5 Miata
1997 MAZDA MX-5 Miata
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SOLENOIDS & SOLENOID VALVES
SOLENOIDS & SOLENOID VALVES
SWITCHES
SWITCHES
MISCELLANEOUS
MISCELLANEOUS
Vehicle Speed Sensor (VSS)On speedometer assembly.
Water Temperature Sender UnitOn center of engine. See Fig. 1 .
Washer Fluid Level SensorOn washer fluid reservoir. See Fig. 1 .
ComponentComponent Location
AT Interlock SolenoidIn steering column, near ignition switch. See Fig. 2 .
EC-AT Solenoid ValveOn left side of transmission.
EGR Solenoid Valve (Vacuum)On right side of engine compartment. See Fig. 1 .
EGR Solenoid Valve (Vent)On right side of engine compartment. See Fig. 1 .
Fourth Gear Solenoid ValveOn left side of transmission.
Idle Air Control ValveOn right side, front of engine compartment. See Fig. 1 .
PRC Solenoid ValveOn right side, front of engine. See Fig. 1 .
Purge Solenoid ValveOn right strut tower. See Fig. 1 .
ComponentComponent Location
Back-Up Lamp Switch (M/T)On right side of transmission. See Fig. 1 .
Brake SwitchOn bracket, above brake pedal. See Fig. 2 .
Buckle SwitchOn driver side seat belt buckle. See Fig. 3 .
Clutch Switch (M/T)On bracket, above clutch pedal. See Fig. 2 .
Hold SwitchUnder right side of center console.
Key Reminder SwitchIn steering column, near ignition switch.
Neutral Switch (M/T)On right side of transmission. See Fig. 1 .
Oil Pressure SwitchOn right side of engine. See Fig. 1 .
"P" Range SwitchUnder center console, on base of gear selector.
Parking Brake SwitchOn base of parking brake lever. See Fig. 4 .
Power Steering Pressure SwitchOn power steering pump assembly.
Refrigerant Pressure SwitchIn front of engine compartment, near radiator support. See Fig. 1 .
Starter Interlock Switch (M/T)On bracket, above clutch pedal. See Fig. 2 .
ThermoswitchUnder right side of dash.
Transmission Range SwitchOn left side of transmission.
ComponentComponent Location

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1997 MAZDA MX-5 Miata
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Fig. 2: Removing & Installing Drive Train Components (Miata)
Courtesy of MAZDA MOTORS CORP.
3. Remove all cooling system hoses and A/T oil cooler hoses at radiator (if equipped). Remove radiator and
cooling fans as an assembly. Remove all drive belts. DO NOT disconnect power steering hoses or A/C
compressor hoses. Unbolt power steering pump and A/C compressor from engine, and wire aside.
4. Remove air cleaner assembly. See Fig. 3
. Remove throttle cable. Note locations and disconnect all
necessary electrical connectors, ground wires, vacuum hoses, fuel hoses, coolant hoses and control cables
for engine removal. Plug all fuel hoses to prevent leakage. Remove engine mount nuts and remove
en
gine.

1997 Mazda MX-5 Miata
1997-98 ENGINES 1.8L 4-Cylinder
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Fig. 5: Removing Engine Components (Protege)
Courtesy of MAZDA MOTORS CORP.
2. Lower vehicle. Remove air cleaner assembly. Remove battery/carrier assembly. Remove throttle cable
and air intake duct across radiator (if equipped).
3. Remove all drive belts. DO NOT disconnect power steering hoses or A/C compressor hoses. Unbolt
power steering pump and A/C compressor from engine, and wire aside.
4. Note locations and disconnect all necessary electrical connectors, ground wires, vacuum hoses, fuel
hoses, coolant hoses and control cables for engine removal.
5. Plug all fuel hoses to avoid leakage. Attach engine support bar or engine hoist to secure engine. Raise
vehicle. Disconnect exhaust manifold down pipe and exhaust brackets from engine. On A/T models,
remove shift control cable.
6. On M/T models, remove shift control linkage and extension bar. Remove clutch release cylinder and fluid
line bracket from transaxle housing, leaving fluid line connected to cylinder. Secure cylinder away from
transaxle.
7. On all models, remove transmission wiring harness connectors and speedometer cable. Remove axle shaft
nuts from hubs. Disconnect stabilizer bar from lower control arms. Separate lower ball joints and steering
tie-rod ends from steering knuckles.
8. Pry axle shafts out of transaxle. Remove and discard circlip from axle shafts. For further information on
axle shafts, see appropriate article in DRIVE AXLES.
9. Remove transaxle mount nuts from crossmember and loosen crossmember bolts. See Fig. 6
. Lower
vehicle and attach engine hoist for engine removal. Remove engine front mount and transaxle top mount
from inner fender panels. Remove transaxle crossmember. Remove engine and transaxle assembly from
top of vehicle.
10. To install, reverse removal procedure. Tighten bolts and nuts to specifications. See TORQUE
SPECIFICATIONS . Fill all fluids to correct level. Prime fuel system before attempting to start engine.
See FUEL PRESSURE RELEASE & PRIMING
. Bleed cooling system. See COOLING SYSTEM
BLEEDING.

1997 Mazda MX-5 Miata
1997-98 ENGINES 1.8L 4-Cylinder
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