NO.9 ABNORMAL SHIFTING [SJ6A-EL]
2016 – MX-5 – Transmission/Transaxle
NO.9 ABNORMAL SHIFTING [SJ6A-EL]
Advice
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When inspecting for incorrect shifting, it is important to determine if there is a malfunction in the electric system or AT.
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If a tire of a different diameter from the standard tire is installed, the TCM determines that the driving mode is the AAS mode, and may change to a different shift timing from the normal timing.
Determining malfunction in electrical system
1. If an error signal is sent to the solenoid simultaneously with the incorrect shifting after monitoring output signals (drive signal for each solenoid), there is a malfunction in the electrical system.
2. Monitor the input signals (signal from each sensor) and determine the input signal which is the cause of the output signal error (drive signal for each solenoid).
The input/output signal can be monitored quickly using the M-MDS. In addition, an instant change in extremely small voltage in the mV unit or ms unit can be monitored using an oscilloscope.
3. An electrical malfunction may occur due to temperature or vibration. For example, even if the system is normal while the engine is cool, a malfunction may occur after warming up the engine or while the vehicle is driven. In this case:
a. Have a solid understanding of the malfunction occurrence mode based on the repair order form.
b. Repeat the malfunction occurrence mode by performing the above procedures 1 and 2, and determine the malfunctioning location while monitoring the electrical signal.
Determining malfunction in mechanical system
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If incorrect shifting is performed regardless of the drive signal (ON—OFF) for each solenoid, there is a malfunction in the mechanical system or AT.
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If clutch slippage occurs, you can smell burnt ATF and it will appear dark and dirty, or the stall speed will increase.
Possible malfunction
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Throttle position sensor, accelerator pedal position sensor malfunction
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The output voltages from the throttle position sensor and accelerator pedal position sensor are important for shift changes. Therefore, shifting may not occur even when the accelerator pedal is depressed if this sensor does not output the correct voltage corresponding to the throttle opening angle and accelerator opening angle.
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Incorrect shifting is indicated if the throttle position sensor output voltage changes automatically even though the accelerator opening angle is maintained.
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AT internal malfunction
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If the signal cycle from the turbine sensor changes due to an AT internal malfunction even if the vehicle speed is maintained, it may cause incorrect shifting.
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Input signal system malfunction (improper characteristics)
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Accelerator pedal position signal
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Throttle position signal
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Engine speed signal
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Engine coolant temperature signal
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Engine torque signal
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Turbine sensor
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Sensor ground
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Speed sensor
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ATF temperature sensor
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Output system solenoid valve malfunction (stuck)
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Pressure control solenoid
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Body ground
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Held in 4th, 5th gear (fail-safe operation)
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Input/output signal system malfunction
The symptom is incorrect shifting because the gear is held in 4th, 5th gear as a fail-safe. In this case, a DTC is stored.
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Poor ground in TCM
If the TCM operation stops due to a poor ground in the TCM, the gear is mechanically held in 4th gear. In this case, a DTC is not stored.
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TCM malfunction
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Clutch slippage, burning (C1 clutch, C2 clutch, C3 clutch, B1 brake, B2 brake, or B3 brake)
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Line pressure is low
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Control valve body system malfunction (operation malfunction, stuck, or oil passage clogging)
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Accumulator system malfunction (operation malfunction, stuck, or oil passage clogging)
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Wheel speed signal error
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Tire malfunction (tire of different diameter from standard tire installed, air pressure other than standard)
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ABS wheel-speed sensor system malfunction (error signal)
Diagnostic procedure
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STEP |
INSPECTION |
ACTION |
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1 |
INSPECT SELECTOR LEVER OPERATION
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Yes |
Go to the next step. |
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No |
Inspect the selector lever and repair or replace the malfunctioning location. (See SELECTOR LEVER INSPECTION.) (See AUTOMATIC TRANSMISSION REMOVAL/INSTALLATION [SJ6A-EL].) |
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2 |
VERIFY DTCs
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Yes |
Perform the applicable DTC troubleshooting. |
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No |
Go to the next step. |
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3 |
INSPECT TIRES
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Yes |
Go to the next step. |
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No |
Replace with a specified tire or adjust the air pressure of each specified tire. |
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4 |
INSPECT WHEEL SPEED SIGNAL
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Yes |
Go to the next step. |
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No |
Inspect the malfunctioning ABS wheel-speed sensor related parts. |
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5 |
INSPECT ATF
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Yes |
Go to the next step. |
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No |
If the ATF amount is insufficient:
If the ATF is extremely dark, dirty or giving off a burnt odor:
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6 |
INSPECT STALL SPEED
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Yes |
Go to the next step. |
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No |
Repair or replace the malfunctioning location. |
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7 |
DETERMINE IF MALFUNCTION CAUSE IS ELECTRICAL SYSTEM OR MECHANICAL SYSTEM
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Yes |
There is an electrical system malfunction. Go to the next step. |
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No |
There is a mechanical system malfunction. Inspect the following items and repair or replace the malfunctioning location.
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8 |
INSPECT ENGINE CONTROL SYSTEM SIGNAL
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Yes |
Go to the next step. |
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No |
Inspect the sensor and wiring harness related to the malfunctioning item, and repair or replace any malfunctioning locations. |
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9 |
INSPECT ATF TEMPERATURE SENSOR
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Yes |
Go to the next step. |
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No |
Inspect the ATF temperature sensor and repair or replace the malfunctioning location. (See TRANSMISSION FLUID TEMPERATURE (TFT) SENSOR INSPECTION [SJ6A-EL].) |
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10 |
INSPECT POWER SUPPLY AND GROUND IN TCM
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Yes |
The following malfunction can be considered because the conventional inspection result is normal.
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No |
Inspect the power supply wiring harness and ground wiring harness (tightening bolt to body) and repair or replace it. |
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