Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Fail-safe Function
The failsafe control function ensures minimum level of drivability even if a fault should occur in the vehicle speed sensors, accelerator pedal position sensor, inhibitor switch, or any of the solenoids.
- Front and rear vehicle speed sensors
A dual speed-sensing system is used. The speed signal is taken from the transmission (by the output shaft speed sensor). Even if one sensor system fails, the vehicle can be controlled normally with the other normally operating sensor system.
- Accelerator pedal position sensor
If the accelerator position sensor becomes faulty, control will be maintained by assuming that the accelerator pedal position is at a certain angle.
- Inhibitor switch
If the TCM receives different signals simultaneously from a faulty inhibitor switch, it selects a range in the following priority:
D > R > N > P
- Line pressure linear solenoid
If the line pressure linear solenoid system fails, the solenoid is de-energized and the line pressure is raised to the maximum to enable the vehicle to operate.
- Lockup duty solenoid
If the lockup duty solenoid system fails, the solenoid is de-energized and the lockup clutch is disengaged.
- Transfer duty solenoid
When the transfer duty solenoid system becomes faulty, it is de-energized. This causes oil pressure to the transfer clutch to be interrupted and no power is transmitted to the rear axle. (FWD state)
- 2-4 brake duty solenoid
If a fault occurs in the 2-4 brake duty solenoid system, the solenoid is de-energized and the gears are limited to the 2nd or 3rd.
- Low clutch duty solenoid
If a fault occurs in the low clutch duty solenoid system, the solenoid is de-energized and the gears are limited to the 3rd or 4th.
- High clutch duty solenoid
If a fault occurs in the high clutch duty solenoid system, the solenoid is de-energized and the gears are limited to the 2nd or 3rd.
- Torque converter turbine speed sensor
If a fault occurs in the torque converter turbine speed sensor, the gears are limited to the 3rd speed.
- Low & reverse duty solenoid
If a fault occurs in the low and reverse duty solenoid system, the solenoid is de-energized and the gears are limited to the 1st.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.