Fail-Safe

TROUBLE DIAGNOSIS


Fail-Safe

The TCM has an electrical fail-safe mode. This mode makes it possible to operate even if there is an error in a main electronic control input/output signal circuit.
In fail-safe mode, even if the selector lever is "D" or "M" mode, the A/T is fixed in 2GR, 4GR and 5GR (depending on the breakdown position), so the customer should feel "slipping" or "poor acceleration".
Even when the electronic circuits are normal, under special conditions (for example, when slamming on the brake with the wheels spinning drastically and stopping the tire rotation), the A/T can go into fail-safe mode. If this happens, switch OFF the ignition switch for 10 seconds, then switch it ON again to return to the normal shift pattern. Therefore, the customer's vehicle has returned to normal, so handle according to the "WORK
FLOW" (Refer to How to Perform Trouble Diagnosis For Quick and Accurate Repair).

FAIL-SAFE FUNCTION
If any malfunction occurs in a sensor or solenoid, this function controls the A/T to mark driving possible.

Output Speed Sensor
Signals are input from two systems - from output speed sensor installed on the A/T and from unified meter and
A/C amp. so normal driving is possible even if there is a malfunction in one of the systems. And if output speed sensor has unusual cases, 5GR and manual mode are prohibited.

Accelerator Pedal Position Sensor
If there is a malfunction in one of the systems, the accelerator opening angle is controlled by ECM according to a pre-determined accelerator angle to make driving possible. And if there are malfunctions in tow systems, the engine speed is fixed by ECM to a pre-determined engine speed to make driving possible.

Throttle Position Sensor
If there is a malfunction in one of the systems, the accelerator opening angle is controlled by ECM according to a pre-determined accelerator angle to make driving possible. And if there are malfunctions in tow systems, the accelerator opening angle is controlled by the idle signal sent from the ECM which is based on input indicating either idle condition or off-idle condition (pre-determined accelerator opening) in order to make driving possible.

Transmission Range Switch
In the unlikely event that a malfunction signal enters the TCM, the position indicator is switched OFF, the starter relay is switched OFF (starter starting is disabled), the back-up lamp relay switched OFF (back-up lamp is OFF) and the position is fixed to the "D" position to make driving possible.

Starter Relay
The starter relay is switched OFF. (Starter starting is disabled.)

Interlock
- If there is an interlock judgment malfunction, the A/T is fixed in 2GR to make driving possible.

NOTE:
When the vehicle is driven fixed in 2GR, an input speed sensor malfunction is displayed, but this is not an input speed sensor malfunction.
- When the coupling pattern below is detected, the fail-safe action corresponding to the pattern is performed.

1st Engine Braking
When there is an 1st engine brake judgment malfunction, the low coast brake solenoid is switched OFF to avoid the engine brake operation.

Line Pressure Solenoid
The solenoid is switched OFF and the line pressure is set to the maximum hydraulic pressure to make driving possible.

Torque Converter Clutch Solenoid
The solenoid is switched OFF to release the lock-up.

Low Coast Brake Solenoid
When a malfunction (electrical or functional) occurs, in order to make driving possible. If the solenoid is ON, the A/T is held in 2GR. If the solenoid is OFF, the A/T is held in 4GR. (Engine brake is not applied in 1GR and
2GR.)

Input Clutch Solenoid
If a malfunction (electrical or functional) occurs with the solenoid either ON or OFF, the A/T is held in 4GR to make driving possible.

Direct Clutch Solenoid
If a malfunction (electrical or functional) occurs with the solenoid either ON or OFF, the A/T is held in 4GR to make driving possible.

Front Brake Solenoid
If a malfunction (electrical or functional) occurs with the solenoid ON, in order to make driving possible. The A/T is held in 5GR. If the solenoid is OFF, the A/T is 4GR.

High and Low Reverse Clutch Solenoid
If a (electrical or functional) malfunction occurs with the solenoid either ON or OFF, the A/T is held in 4GR to make driving possible.

Input Speed Sensor 1 or 2
The control is the same as if there were no input speed sensors, 5GR and manual mode are prohibited.