Fail Safe

Fail-Safe
The TCM has an electrical fail-safe mode. This mode makes it possible to operate even if there is a malfunction in a main electronic control input/output signal circuit.

In fail-safe mode, even if the select lever is "D" or "M" mode, the transmission is fixed in 2nd, 4th, or 5th (depending on the breakdown position), so the customer should feel "slipping" or "poor acceleration". When fail-safe mode is triggered, when the ignition switch is switched "ON", the A/T CHECK indicator lamp flashes for about 8 seconds. (Refer to "TCM SELF-DIAGNOSTIC PROCEDURE (NO TOOLS)").

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 transmission 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. Also, the A/T CHECK indicator lamp flashes for about 8 seconds once, then is cleared. Therefore, the customer's vehicle has returned to normal, so handle according to the "diagnostics flow".

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

Vehicle Speed Sensor
^ Signals are input from two systems - from vehicle speed sensor A/T (revolution sensor) installed on the transmission and from combination meter so normal driving is possible even if there is a malfunction in one of the systems. And if vehicle speed sensor A/T (revolution sensor) has unusual cases, 5th gear 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.

PNP 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), and the position is fixed to the "D" range to make driving possible.

PNP Relay
^ The PNP relay is switched "OFF". (Starter starting is disabled.)

A/T Interlock
^ If there is an A/T interlock judgment malfunction, the transmission is fixed in 2nd gear, 4th gear, or 5th gear to make driving possible.

NOTE: When the vehicle is driven fixed in 2nd gear or 5th gear, a turbine revolution sensor malfunction is displayed, but this is not a turbine revolution sensor malfunction.

^ When the coupling pattern is detected, the fail-safe action corresponding to the pattern is executed.





A/T INTERLOCK COUPLING PATTERN TABLE

A/T 1st Engine Braking
^ When there is an A/T first gear 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 (electrical or functional) malfunction occurs, in order to make driving possible, if the solenoid is "ON", the transmission is held in 2nd gear; if the solenoid is "OFF", the transmission is held in 4th gear. (engine brake is not applied in 1st and 2nd gear.)

Input Clutch Solenoid
^ If a (electrical or functional) malfunction occurs with the solenoid either "ON" or "OFF", the transmission is held in 4th gear to make driving possible.

Direct Clutch Solenoid
^ If a (electrical or functional) malfunction occurs with the solenoid either "ON" or "OFF", the transmission is held in 4th near to make driving possible.

Front Brake Clutch Solenoid
^ If a (electrical or functional) malfunction occurs with the solenoid "ON", in order to make driving possible, the A/T is held in 5th gear; if the solenoid is OFF, 4th gear.

High and Low Reverse Clutch Solenoid
^ If a (electrical or functional) malfunction occurs with the solenoid either "ON" or "OFF", the transmission is held in 4th gear to make driving possible.

Turbine Revolution Sensor 1 or 2
^ The control is the same as if there were no turbine revolution sensors, 5th gear and manual mode are prohibited.