Fail-safe Function

The fail-safe control function ensures minimum level of driveability even if a fault should occur in the vehicle speed sensors, throttle 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.

  If both the front and rear vehicle speed sensors become faulty, the vehicle is made to operate only in the 3rd speed.

• Throttle position sensor

  If the throttle position sensor becomes faulty, control will be maintained by assuming that the throttle opening 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 > N (P) > R > 3 > 2 > 1 >

• Shift solenoid 1 and 2

  If a fault occurs in either of solenoids 1 and 2, both the solenoids are de-energized, and the gear is held in the 3rd. If both the solenoids should fail, the TCM invariably selects and keeps the 3rd gear.

• Line pressure duty solenoid

  If the line pressure duty solenoid 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 fails, the solenoid is de-energized and the lockup clutch is disengaged.

• Transfer duty solenoid

  When the transfer duty solenoid becomes faulty, it is de-energized. This causes maximum oil pressure to be applied to the transfer clutch so that the power is always transmitted to the rear axle (direct-coupled AWD condition).

• 2-4 brake duty solenoid

  If a fault occurs in the 2-4 brake duty solenoid, the solenoid is de-energized and the usable gears are limited to the 1st and 3rd.

• Low-clutch timing solenoid

  If a fault occurs in the low clutch timing solenoid, the solenoid is de-energized and the usable gears are limited to the 1st and 3rd.

• 2-4 brake timing solenoid

  If a fault occurs in the 2-4 brake timing solenoid, the solenoid is de-energized and the usable gears are limited to the 1st and 3rd.

• Torque converter turbine speed sensor

  If a fault occurs in the torque converter turbine speed sensor, the usable gears are limited to the 3rd.