Shift MAZDA MIATA 1997 Factory Repair Manual

1997 AUTOMATIC TRANSMISSIONS
NC4A-EL Electronic Controls
APPLICATION
TRANSMISSION APPLICATION
DESCRIPTION
The NC4A-EL series is a 4-speed electronically controlled automatic transmission. Five solenoids attached to
valve body control shift changes. Solenoids are controlled by the Transmission Control Module (TCM).
The TCM receives information from various input devices. The TCM uses this information to control following
solenoids:
Shift solenoids for transmission shifting.
Torque Converter Clutch (TCC) solenoid for torque converter clutch lock-up.
3-2 control solenoid for downshift timing control.
A HOLD switch is mounted on the shift lever. HOLD function may be activated in "D", "S" or "L" gears by
pressing HOLD button. In "L" and "S" positions, vehicle is held in selected gear and no upshift or downshift
takes place. This function is used for driving up steep inclines or for engine braking assistance when descending
steep grades. If activated in "D" position a 1-2 and 2-3 upshift is permitted when starting from a stop, but after
the 2-3 upshift the vehicle is locked in "D" until it comes to a complete stop. The 1-2 and 2-3 upshift pattern is
changed to a "short shift" specification. This function is used for starting off or driving on slippery surfaces.
Pushin
g HOLD button again deactivates system.
VehicleTransmission Model
MiataNC4A-EL
CAUTION: Vehicle is equipped with Supplemental Restraint System (SRS). When
servicing vehicle, use care to avoid accidental air bag deployment. SRS-
related components are located in steering column, center console and
instrument panel. DO NOT use electrical test equipment on these circuits.
If necessary, deactivate SRS before servicing components. See AIR BAG
DEACTIVATION PROCEDURES article in GENERAL INFORMATION.
CAUTION: Disconnecting battery on models equipped with anti-theft radio require
canceling of anti-theft operation. See appropriate AUTOMATIC
TRANSMISSION SERVICING article in TRANSMISSION SERVICING. Refer
to vehicle owner's manual to identify radio type.
NOTE: Torque Converter Clutch (TCC) solenoid is also known as lock-up solenoid,
TCC lock-up or 4th gear solenoid.

1997 Mazda MX-5 Miata
1997 AUTOMATIC TRANSMISSIONS NC4A-EL Electronic Controls

1997 Mazda MX-5 Miata
1997 AUTOMATIC TRANSMISSIONS NC4A-EL Electronic Controls
Microsoft
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OPERATION
TCM
TCM receives information from various input devices and uses this information to control solenoids on
transmission valve body for transmission shifting and torque converter clutch engagement.
TCM automatically switches from NORMAL mode to POWER mode corresponding to driving condition in
"D" range. Upshifts and downshifts are performed at a higher speed in POWER mode than in NORMAL mode.
TCM contains a self-diagnostic system, which will store Diagnostic Trouble Codes (DTC) if a failure or
problem exists in electronic control system. DTC can be retrieved to determine problem area. See SELF-
DIAGNOSTIC SYSTEM . TCM is located under left side of instrument panel, above fuse block.
TCM INPUT DEVICES & SIGNALS
4th Gear Inhibit Signal
Signal is input to TCM when cruise control is on. Signal detects when difference between target speed and
actual speed exceeds specification.
HOLD Switch
HOLD switch delivers input to TCM to indicate gears preferred by operator. Switch is located on shift lever
handle. HOLD switch is canceled when ignition switch is turned off.
Input/Turbine Speed Sensor
Sensor is a magnetic pick-up type pulse generator that monitors input shaft speed. AC waveform is input to
TCM by output speed sensor. Sensor is located on front of transmission, back of converter housing.
Throttle Position (TP) Sensor
TP sensor delivers an input signal to TCM indicating throttle valve position (opening). TP sensor is located on
side of throttle body.
Transmission Range Switch
Transmission range switch delivers an input signal to TCM indicating shift lever position. Switch is located on
side of transmission.
Transmission Fluid Temperature (TFT) Sensor
TFT sensor is threaded into cooler line banjo mounting on side of transmission case. Sensor sends signal to
TCM indicating fluid temperature.
Vehicle Speed Sensor

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1997 AUTOMATIC TRANSMISSIONS NC4A-EL Electronic Controls
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Sensor is a cable driven pulse generator that is part of speedometer. Pulse signals are sent to TCM.
TCM OUTPUT DEVICES
HOLD Indicator Light
Receives signal from TCM to indicate switch position.
Inhibitor Signal
When shift selector lever is moved from Park or Neutral to another gear, signal is sent from TCM to ECM to
regulate fuel injection volume for shift shock prevention.
Shift Solenoids & 3-2 Control Solenoid
The TCM controls transmission shifting by delivering an output signal to operate proper solenoid. 3-2 control
solenoid affects downshift timing. See SOLENOID OPERATION
table. Hydraulic pressure is retained when
solenoid is off and drained when solenoid is on. Solenoids are located on transmission valve body. See Fig. 1
.
SOLENOID OPERATION
TCC Solenoid Valve
Solenoid valve is ON/OFF type controlled by TCM. Solenoid regulates pilot pressure to applied to lock-up
control plug. Hydraulic pressure is retained when solenoid is on and drained when solenoid is off. Solenoid is
located on side of case. See Fig. 1
.
Shift Lever Position1-2 Shift Solenoid2-3 Shift Solenoid
3-4 Shift
Solenoid
"D" (Drive)
1st GearOnOnOn
2nd GearOffOnOn
3rd GearOffOffOn
4th GearOffOffOff
"2" (Second)
1st GearOnOnOn
2nd GearOffOnOn
"L" (Low)
1st GearOnOnOn
"R" (Reverse)OffOffOn
"N" or "P"OnOnOn

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1997 AUTOMATIC TRANSMISSIONS NC4A-EL Electronic Controls
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Fig. 1: Locating Solenoid Valves
Courtesy of MAZDA MOTORS CORP.
SELF-DIAGNOSTIC SYSTEM
SYSTEM DIAGNOSIS
TCM monitors transmission operation and contains a self-diagnostic system which stores a Diagnostic Trouble
Code (DTC) if an electronic control system failure or component malfunction exists. If a problem exists in any
of the solenoids or speed sensors and DTC is set, TCM will deliver a signal to blink the HOLD indicator light
on instrument panel to warn the driver. DTC may be set if a failure exists and can be retrieved for transmission
diagnosis.
RETRIEVING TROUBLE CODES
NOTE: Before testing transmission, ensure fluid level is correct. Ensure engine starts
with shift lever in Park and Neutral to ensure proper adjustment of transmission
range switch. Transmission Control Module (TCM) must first be checked for
stored codes. See RETRIEVING TROUBLE CODES
.
NOTE: Before retrieving DTC, ensure proper battery voltage exists for self-diagnostic
system operation. If any DTC are present other than those listed below, see

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1997 AUTOMATIC TRANSMISSIONS NC4A-EL Electronic Controls
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CLEARING CODES
To clear DTC stored in TCM, use scan tool. See scan tool instruction manual. Road test vehicle.
COMPONENT LOCATION
COMPONENT LOCATION
COMPONENT CONNECTOR IDENTIFICATION
P0706 Transmission Range Sensor Range/Performance
P0710 (2) TFT Sensor Malfunction
P0711 (2) TFT Sensor Range/Performance
P0715 Input/Turbine Speed Sensor
P0725 Engine Speed Input Circuit Malfunction
P0731 Incorrect 1st Gear Ratio
P0732 Incorrect 2nd Gear Ratio
P0733 Incorrect 3rd Gear Ratio
P0734 Incorrect 4th Gear Ratio
P0740 TCC System Malfunction
P0750 1-2 Shift Solenoid
P0755 2-3 Shift Solenoid
P0760 3-4 Shift Solenoid
P1720 Vehicle Speed Sensor
P1743 Lock-Up Solenoid Valve
P1765 3-2 Timing Control Solenoid Valve
P1790 Throttle Position Sensor
P1795 Idle Switch
(1)Check listed component for probable cause. Check wiring and connection of specified component.
(2)Transmission Fluid Temperature.
DescriptionLocation
Engine Control ModuleBehind Passenger Seat
Input/Turbine Speed SensorMounted To 4th Gear Case
Shift SolenoidsSee Fig. 1
TCC Lock-Up SolenoidSee Fig. 1
Transmission Control UnitAbove Fuse Box
3-2 Control ValveSee Fig. 1
TFT SensorMounted In-Line To Cooler Line
Vehicle Speed SensorMounted In Speedometer

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1997 AUTOMATIC TRANSMISSIONS NC4A-EL Electronic Controls
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Condition
TCM outputs solenoid pattern of 1st gear when gear ratio is other than 1st gear. Possible causes are:
Low ATF level.
Low line pressure.
Control valve stuck.
Solenoid valve malfunction.
TCM malfunction.
Diagnosis & Repair Procedure
1. Ensure ATF level and condition is okay. Check line pressure and stall speed. See LINE PRESSURE
TEST and STALL SPEED under TESTING in MAZDA NC4A-EL OVERHAUL article. Repair any
components as necessary. If malfunction is not present, go to next step.
2. Inspect 1-2, 2-3 and 3-4 shift solenoid valves. See SOLENOID VALVES
under COMPONENT
TESTING. Repair as needed. If solenoid valves are okay, go to next step.
3. Inspect valve body. Ensure all valves operate smoothly. Repair as needed. If valve body is okay, go to
next step.
4. Clear DTC and retest. See CLEARING CODES
. If code P0731 is still present, replace TCM. If code is
no longer present and symptom still exists, problem may be caused by intermittent clutch slippage.
Further investigation may be required. See MAZDA NC4A-EL OVERHAUL article.
DTC P0732: INCORRECT 2ND GEAR RATIO
Condition
TCM outputs solenoid pattern of 2nd gear when gear ratio is other than 2nd gear. Possible causes are:
Low ATF level.
Direct clutch slippage.
One-way clutch slippage.
Faulty band servo.
Low line pressure.
Control valve stuck.
Solenoid valve malfunction.
TCM malfunction.
Diagnosis & Repair Procedure
NOTE: If any following DTC is also present, repair it first and then proceed with this
test: DTC P0750
, P0755 , P0760 .

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1. Ensure ATF level and condition is okay. Check line pressure and stall speed. See LINE PRESSURE
TEST and STALL SPEED under TESTING in MAZDA NC4A-EL OVERHAUL article. Repair any
components as necessary. If malfunction is not present, go to next step.
2. Inspect 1-2, 2-3 and 3-4 shift solenoid valves. See SOLENOID VALVES
under COMPONENT
TESTING. Repair as needed. If solenoid valves are okay, go to next step.
3. Inspect valve body. Ensure all valves operate smoothly. Repair as needed. If valve body is okay, go to
next step.
4. Clear DTC and retest. See CLEARING CODES
. If code P0732 is still present, replace PCM. If code is
no longer present and symptom still exists, problem may be caused by intermittent clutch slippage.
Further investigation may be required. See MAZDA NC4A-EL OVERHAUL article.
DTC P0733: INCORRECT 3RD GEAR RATIO
Condition
TCM outputs solenoid pattern of 3rd gear when gear ratio is other than 3rd gear. Possible causes are:
Low ATF level.
Direct clutch slippage.
One-way clutch slippage.
Front clutch slippage.
Low line pressure.
Control valve stuck.
Solenoid valve malfunction.
TCM malfunction.
Diagnosis & Repair Procedure
1. Ensure ATF level and condition is okay. Check line pressure and stall speed. See LINE PRESSURE
TEST and STALL SPEED under TESTING in MAZDA NC4A-EL OVERHAUL article. Repair any
components as necessary. If malfunction is not present, go to next step.
2. Inspect 1-2, 2-3 and 3-4 shift solenoid valves. See SOLENOID VALVES
under COMPONENT
TESTING. Repair as needed. If solenoid valves are okay, go to next step.
3. Inspect valve body. Ensure all valves operate smoothly. Repair as needed. If valve body is okay, go to
next step.
4. Clear DTC and retest. See CLEARING CODES
. If DTC P0733 is still present, replace PCM. If code is
no longer present and symptom still exists, problem may be caused by intermittent clutch slippage.
Further investigation may be required. See MAZDA NC4A-EL OVERHAUL article.
DTC P0734: INCORRECT 4TH GEAR RATIO 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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Condition
TCM outputs solenoid pattern of 3rd gear when gear ratio is other than 3rd gear. Possible causes are:
Low ATF level.
Band servo slippage.
Front clutch slippage.
Low line pressure.
Control valve stuck.
Solenoid valve malfunction.
TCM malfunction.
Diagnosis & Repair Procedure
1. Ensure ATF level and condition is okay. Check line pressure and stall speed. See LINE PRESSURE
TEST and STALL SPEED under TESTING in MAZDA NC4A-EL OVERHAUL article. Repair any
components as necessary. If malfunction is not present, go to next step.
2. Inspect 1-2, 2-3 and 3-4 shift solenoid valves. See SOLENOID VALVES
under COMPONENT
TESTING. Repair as needed. If solenoid valves are okay, go to next step.
3. Inspect valve body. Ensure all valves operate smoothly. Repair as needed. If valve body is okay, go to
next step.
4. Clear DTC and retest. See CLEARING CODES
. If DTC P0734 is still present, replace PCM. If code is
no longer present and symptom still exists, problem may be caused by intermittent clutch slippage.
Further investigation may be required. See MAZDA NC4A-EL OVERHAUL article.
DTC P0740: TORQUE CONVERTER CLUTCH MALFUNCTION
Condition
TCM outputs TCC signal, but TCC does not operate. Possible causes are:
Low ATF level.
Low line pressure.
Torque converter slippage.
Control valve stuck.
Lock-up solenoid valve malfunction.
TCM malfunction.
Diagnosis & Repair Procedure
NOTE: If any following DTC is also present, repair it first and then proceed with this
test: DTC P0750
, P0755 , P0760 .

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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.

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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. 2G (Orange 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. 2G. 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 2-3 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 trouble codes and road test vehicle. Retrieve DTC. If DTC P0755 is still present, replace TCM. If
code is no longer present, system is okay.
DTC P0760: 3-4 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. 2I (Blue 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 3-4 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 codes and road test vehicle. Retrieve DTC. If DTC P0760 is still present, replace TCM. If code is
no longer present, problem is intermittent. Further investigation may be necessary.
DTC P1720: VEHICLE SPEED SENSOR SIGNAL MISSING

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