Toyota Tundra Service Manual: Fail-safe Chart

FAIL-SAFE CHART

1. Fail-safe

This function minimizes the loss of ECT functions when a malfunction occurs in a sensor or solenoid.

2. Fail-safe control list

Malfunctioning Part

Function

DTC P0717:

Input Speed Sensor NT

During an input speed sensor malfunction, shift control is performed using the output speed sensor SP2 signal.

During an input speed sensor malfunction, up-shift to 5th and 6th, AI-SHIFT and flex lock-up clutch control are prohibited.

DTC P0722:

Output Speed Sensor SP2

During an output speed sensor malfunction, shift control is performed using the input speed sensor NT signal.

During an output speed sensor malfunction, up-shift to 5th and 6th, AI-SHIFT and flex lock-up clutch control are prohibited.

DTC P0712, P0713:

ATF Temperature Sensor

During an ATF temperature sensor malfunction, up-shift to 5th and 6th, and flex lock-up clutch control are prohibited.

Shift Solenoid Valve S1, S2, S3, S4 and SR

The current to the malfunctioning solenoid valve is cut off and control is performed by operating the other normal solenoid valves.

Shift control is performed depending on the failed solenoid as described in the table below.

DTC P0748, P0778:

Shift Solenoid Valve SL1 and SL2

During a solenoid valve SL1 or SL2 malfunction, up-shift to 5th and 6th, and flex lock-up clutch control are prohibited.

DTC P2714, P2716:

Shift Solenoid Valve SLT

During a solenoid valve SLT malfunction, the current to the solenoid valve is stopped. This stops optimal line pressure control and shift shock increases. However, shifting is performed using normal clutch pressure control.

DTC P2757, P2759:

Shift Solenoid Valve SLU

During a solenoid valve SLU malfunction, the current to the solenoid valve is stopped. This stops lock-up control and flex lock-up control, and fuel economy decreases.

Shift Solenoid Valve Normal Operation Chart

Shift Lever Position

Gear

Shift Solenoid S1

Shift Solenoid S2

Shift Solenoid S3

Shift Solenoid S4

Shift Solenoid SR

Shift Solenoid SL1

Shift Solenoid SL2

D, S6

1st

OFF

ON

ON

OFF

ON

OFF

ON

2nd

ON

ON

ON

OFF

ON

OFF

ON

3rd

ON

OFF

ON

OFF

ON

OFF

ON

4th

ON

OFF

OFF

OFF

ON

OFF

ON

5th

ON

OFF

OFF

ON

OFF

ON

OFF

6th

ON

ON

OFF

ON

OFF

ON

OFF

S5

1st

OFF

ON

ON

OFF

ON

OFF

ON

2nd

ON

ON

ON

OFF

ON

OFF

ON

3rd

ON

OFF

ON

OFF

ON

OFF

ON

4th

ON

OFF

OFF

OFF

ON

OFF

ON

5th

ON

OFF

OFF

ON

OFF

ON

OFF

S4

1st

OFF

ON

ON

OFF

ON

OFF

ON

2nd

ON

ON

ON

OFF

ON

OFF

ON

3rd

ON

OFF

ON

OFF

ON

OFF

ON

4th

ON

OFF

OFF

OFF

ON

OFF

ON

S3

1st

OFF

ON

ON

OFF

ON

OFF

ON

2nd

ON

ON

ON

OFF

ON

OFF

ON

3rd (E/B)

ON

OFF

ON

OFF

ON

OFF

OFF

S2

1st

OFF

ON

ON

OFF

ON

OFF

ON

2nd (E/B)

ON

ON

ON

ON

ON

OFF

OFF

S1

1st (E/B)

OFF

ON

ON

OFF

ON

OFF

OFF

(a) Fail-safe operation for electronically malfunctioning shift solenoid valve (S1, S2, S3, S4 and SR).

(1) Fail-safe function

If any of the shift solenoid valve circuits has an open or short failure, the ECM turns the other shift solenoids ON and OFF in order to shift into the gear positions shown in the table below. Also, the ECM stops sending current to the open or short-circuited solenoid.

Even if starting the engine again in the fail-safe mode, the gear position remains in the same position.

HINT:

  • *: Actual gear shift (gear position) under fail-safe operation.
  • X: OFF (the ECM stops sending current to the malfunctioning solenoid valve).
  • Electrical malfunction: Condition is shown to the left of the "→".
  • Fail-safe mode: Condition is shown to the right of the "→".
  • E/B: Engine brake
Shift Solenoid Valve S1 Electrical Malfunction (P0973, P0974)

Shift Lever Position

Gear*

Shift Solenoid S1

Shift Solenoid S2

Shift Solenoid S3

Shift Solenoid S4

Shift Solenoid SR

Shift Solenoid SL1

Shift Solenoid SL2

D, S6

1st

X

ON

ON

OFF

ON

OFF

ON

1st → 4th

X

ON → OFF

ON → OFF

OFF

ON

OFF

ON

3rd → 4th

X

OFF

ON → OFF

OFF

ON

OFF

ON

4th

X

OFF

OFF

OFF

ON

OFF

ON

5th

X

OFF

OFF

ON

OFF

ON

OFF

N → 5th

X

ON → OFF

OFF

ON

OFF

ON

OFF

S5

1st

X

ON

ON

OFF

ON

OFF

ON

1st → 4th

X

ON → OFF

ON → OFF

OFF

ON

OFF

ON

3rd → 4th

X

OFF

ON → OFF

OFF

ON

OFF

ON

4th

X

OFF

OFF

OFF

ON

OFF

ON

5th

X

OFF

OFF

ON

OFF

ON

OFF

S4

1st

X

ON

ON

OFF

ON

OFF

ON

1st → 4th

X

ON → OFF

ON → OFF

OFF

ON

OFF

ON

3rd → 4th

X

OFF

ON → OFF

OFF

ON

OFF

ON

4th

X

OFF

OFF

OFF

ON

OFF

ON

S3

1st

X

ON

ON

OFF

ON

OFF

ON

1st → 4th

X

ON → OFF

ON → OFF

OFF

ON

OFF

ON

3rd (E/B) → 4th

X

OFF

ON → OFF

OFF

ON

OFF

OFF → ON

S2

1st

X

ON

ON

OFF

ON

OFF

ON

2nd (E/B) → 4th

X

ON → OFF

ON → OFF

ON → OFF

ON

OFF

OFF → ON

S1

1st (E/B)

X

ON

ON

OFF

ON

OFF

OFF

Shift Solenoid Valve S2 Electrical Malfunction (P0976, P0977)

Shift Lever Position

Gear*

Shift Solenoid S1

Shift Solenoid S2

Shift Solenoid S3

Shift Solenoid S4

Shift Solenoid SR

Shift Solenoid SL1

Shift Solenoid SL2

D, S6

3rd

OFF → ON

X

ON

OFF

ON

OFF

ON

3rd

ON

X

ON

OFF

ON

OFF

ON

3rd

ON

X

ON

OFF

ON

OFF

ON

4th

ON

X

OFF

OFF

ON

OFF

ON

5th

ON

X

OFF

ON

OFF

ON

OFF

5th

ON

X

OFF

ON

OFF

ON

OFF

S5

3rd

OFF → ON

X

ON

OFF

ON

OFF

ON

3rd

ON

X

ON

OFF

ON

OFF

ON

3rd

ON

X

ON

OFF

ON

OFF

ON

4th

ON

X

OFF

OFF

ON

OFF

ON

5th

ON

X

OFF

ON

OFF

ON

OFF

S4

3rd

OFF → ON

X

ON

OFF

ON

OFF

ON

3rd

ON

X

ON

OFF

ON

OFF

ON

3rd

ON

X

ON

OFF

ON

OFF

ON

4th

ON

X

OFF

OFF

ON

OFF

ON

S3

3rd → 3rd (E/B)

OFF → ON

X

ON

OFF

ON

OFF

ON → OFF

3rd → 3rd (E/B)

ON

X

ON

OFF

ON

OFF

ON → OFF

3rd (E/B)

ON

X

ON

OFF

ON

OFF

OFF

S2

3rd → 3rd (E/B)

OFF → ON

X

ON

OFF

ON

ON → OFF

ON → OFF

3rd (E/B)

ON

X

ON

ON → OFF

ON

OFF

OFF

S1

3rd (E/B)

OFF → ON

X

ON

OFF

ON

OFF

OFF

Shift Solenoid Valve S3 Electrical Malfunction (P0979, P0980)

Shift Lever Position

Gear*

Shift Solenoid S1

Shift Solenoid S2

Shift Solenoid S3

Shift Solenoid S4

Shift Solenoid SR

Shift Solenoid SL1

Shift Solenoid SL2

D, S6

3rd → 4th

OFF

ON

X

OFF

ON

OFF

ON

4th

ON

ON → OFF

X

OFF

ON

OFF

ON

4th

ON

OFF

X

OFF

ON

OFF

ON

4th

ON

OFF

X

OFF

ON

OFF

ON

5th

ON

OFF

X

ON

OFF

ON

OFF

6th

ON

ON

X

ON

OFF

ON

OFF

S5

3rd

OFF

ON

X

OFF

ON

OFF

ON

4th

ON

ON → OFF

X

OFF

ON

OFF

ON

4th

ON

OFF

X

OFF

ON

OFF

ON

4th

ON

OFF

X

OFF

ON

OFF

ON

5th

ON

OFF

X

ON

OFF

ON

OFF

S4

3rd

OFF

ON

X

OFF

ON

OFF

ON

4th

ON

ON → OFF

X

OFF

ON

OFF

ON

4th

ON

OFF

X

OFF

ON

OFF

ON

4th

ON

OFF

X

OFF

ON

OFF

ON

S3

3rd

OFF

ON

X

OFF

ON

OFF

ON

4th

ON

ON → OFF

X

OFF

ON

OFF

ON

4th

ON

OFF

X

OFF

ON

OFF

OFF → ON

S2

3rd

OFF

ON

X

OFF

ON

OFF

ON

6th → 4th

ON

ON → OFF

X

ON → OFF

ON

OFF

OFF → ON

S1

1st

OFF

ON

X

OFF

ON

OFF

OFF

Shift Solenoid Valve S4 Electrical Malfunction (P0982, P0983)

Shift Lever Position

Gear*

Shift Solenoid S1

Shift Solenoid S2

Shift Solenoid S3

Shift Solenoid S4

Shift Solenoid SR

Shift Solenoid SL1

Shift Solenoid SL2

D, S6

1st

OFF

ON

ON

X

ON

OFF

ON

2nd

ON

ON

ON

X

ON

OFF

ON

3rd

ON

OFF

ON

X

ON

OFF

ON

4th

ON

OFF

OFF

X

ON

OFF

ON

4th

ON

OFF

OFF

X

OFF → ON

ON → OFF

OFF → ON

4th

ON

ON → OFF

OFF

X

OFF → ON

ON → OFF

OFF → ON

S5

1st

OFF

ON

ON

X

ON

OFF

ON

2nd

ON

ON

ON

X

ON

OFF

ON

3rd

ON

OFF

ON

X

ON

OFF

ON

4th

ON

OFF

OFF

X

ON

OFF

ON

4th

ON

OFF

OFF

X

OFF → ON

ON → OFF

OFF → ON

S4

1st

OFF

ON

ON

X

ON

OFF

ON

2nd

ON

ON

ON

X

ON

OFF

ON

3rd

ON

OFF

ON

X

ON

OFF

ON

4th

ON

OFF

OFF

X

ON

OFF

ON

S3

1st

OFF

ON

ON

X

ON

OFF

ON

2nd

ON

ON

ON

X

ON

OFF

ON

3rd (E/B)

ON

OFF

ON

X

ON

OFF

OFF

S2

1st

OFF

ON

ON

X

ON

OFF

ON

2nd (E/B)

ON

ON

ON

X

ON

OFF

OFF

S1

1st (E/B)

OFF

ON

ON

X

ON

OFF

OFF

Shift Solenoid Valve SR Electrical Malfunction (P0985, P0986)

Shift Lever Position

Gear*

Shift Solenoid S1

Shift Solenoid S2

Shift Solenoid S3

Shift Solenoid S4

Shift Solenoid SR

Shift Solenoid SL1

Shift Solenoid SL2

D, S6

1st

OFF

ON

ON

OFF

X

OFF

ON

2nd

ON

ON

ON

OFF

X

OFF

ON

3rd

ON

OFF

ON

OFF

X

OFF

ON

4th

ON

OFF

OFF

OFF

X

OFF

ON

5th

ON

OFF

OFF

ON

X

ON

OFF

6th

ON

ON

OFF

ON

X

ON

OFF

S5

1st

OFF

ON

ON

OFF

X

OFF

ON

2nd

ON

ON

ON

OFF

X

OFF

ON

3rd

ON

OFF

ON

OFF

X

OFF

ON

4th

ON

OFF

OFF

OFF

X

OFF

ON

5th

ON

OFF

OFF

ON

X

ON

OFF

S4

1st

OFF

ON

ON

OFF

X

OFF

ON

2nd

ON

ON

ON

OFF

X

OFF

ON

3rd

ON

OFF

ON

OFF

X

OFF

ON

4th

ON

OFF

OFF

OFF

X

OFF

ON

S3

1st

OFF

ON

ON

OFF

X

OFF

ON

2nd

ON

ON

ON

OFF

X

OFF

ON

3rd (E/B)

ON

OFF

ON

OFF

X

OFF

OFF

S2

1st

OFF

ON

ON

OFF

X

OFF

ON

2nd (E/B)

ON

ON

ON

ON

X

OFF

OFF

S1

1st (E/B)

OFF

ON

ON

OFF

X

OFF

OFF

(b) Fail-safe operation in the event of a mechanical system malfunction.

(1) Fail-safe function

The ECM controls the gear position as shown in the table below when malfunctions occur.

DTC

Condition

Gear*1

-

Normal

1st

2nd

3rd

4th

5th

6th

P0751

Shift solenoid valve S1:

Stuck OFF malfunction

1st*2

1st*2

3rd

3rd

3rd

3rd

P0761

Shift solenoid valve S3:

Stuck ON malfunction

1st

2nd

3rd

3rd

3rd

3rd

P0766

P0776

Shift solenoid valve S4, shift solenoid valve SL2 or valve body (brake control valve):

Malfunction

1st

2nd

3rd

3rd

3rd

3rd

P0781

Valve body (1-2 shift valve):

Malfunction

1st*2

1st*2

3rd

3rd

3rd

3rd

P0729

Valve body (sequence valve):

Malfunction

1st

2nd

3rd

3rd

3rd

3rd

HINT:

  • *1: Actual gear shift (gear position) under fail-safe operation.
  • *2: Under engine braking, downshifting to 1st or 2nd gear is prohibited.
    Dtc Check / Clear

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