NO.9 ABNORMAL SHIFTING [SJ6A-EL]

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Advice

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:

(1)  Have a solid understanding of the malfunction occurrence mode based on the repair order form.

(2)  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

•  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.

•  If clutch slippage occurs, you can smell burnt ATF and it will appear dark and dirty, or the stall speed will increase.

Possible malfunction

―  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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―  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.

―  Accelerator pedal position signal

―  Throttle position signal

―  Engine speed signal

―  Engine coolant temperature signal

―  Engine torque signal

―  Turbine sensor

―  Sensor ground

―  Speed sensor

―  ATF temperature sensor

―  Pressure control solenoid

―  Body ground

―  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.

―  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.

―  TCM malfunction

―  Tire malfunction (tire of different diameter from standard tire installed, air pressure other than standard)

―  ABS wheel-speed sensor system malfunction (error signal)

Diagnostic procedure