K120 / K121 (CVT): K120 CONTINUOUSLY VARIABLE TRANSAXLE SYSTEM: P07757F; Pressure Control Solenoid "B" Actuator Stuck Off; 2019 - 2025 MY Corolla Corolla Hatchback [06/2018

Last Modified: 07-31-2024	6.11:8.1.0	Doc ID: RM100000001D0XL
Model Year Start: 2019	Model: Corolla Hatchback	Prod Date Range: [06/2018 - ]
Title: K120 / K121 (CVT): K120 CONTINUOUSLY VARIABLE TRANSAXLE SYSTEM: P07757F; Pressure Control Solenoid "B" Actuator Stuck Off; 2019 - 2025 MY Corolla Corolla Hatchback [06/2018 - ]

DTC

P07757F

Pressure Control Solenoid "B" Actuator Stuck Off

DESCRIPTION

Using the current from the TCM, the shift solenoid valve SL2 controls the C2 clutch pressure in accordance with the requested shift mode.

When the TCM requests the shift mode to be changed to belt mode, the C2 clutch is engaged and the input torque is transmitted to the output shaft via the steel belt.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

MIL

Memory

Note

P07757F

Pressure Control Solenoid "B" Actuator Stuck Off

Any of the following conditions are met (2-trip detection logic):

When the TCM commands the C2 clutch to be engaged, the difference between the signals from the transmission revolution sensor (NSS) and (NOUT) is more than 300 rpm for 2 seconds or more.
When the TCM commands the C1 clutch to be engaged, the difference between the signals from the transmission revolution sensor (NT) and (NC1) is more than 200 rpm for 1 second or more.

Transmission valve body assembly (shift solenoid valve SL2)
Continuously variable transaxle assembly

Comes on

DTC stored

SAE Code:

P0776

DTC Detection Condition Patterns:

		Vehicle Condition
		Pattern 1	Pattern 2
Diagnostic Condition	TCM commands the C2 clutch to be engaged	○	-
Diagnostic Condition	TCM commands the C1 clutch to be engaged	-	○
Malfunction Condition	Difference between the signals from the transmission revolution sensor (NSS) and (NOUT) is more than 300 rpm	○	-
Malfunction Condition	Difference between the signals from the transmission revolution sensor (NT) and (NC1) is more than 200 rpm	-	○
Duration		2 seconds or more	1 second or more
Detection Logic		2-trip detection logic	2-trip detection logic

HINT:

This DTC is stored when any of the above detection patterns is met.

MONITOR DESCRIPTION

When the TCM requests the shift mode to be changed to belt mode, the shift solenoid valve SL2 is turned ON and the C2 clutch is engaged. As a result, the transmission revolution sensor (NSS) signal becomes equal to the transmission revolution sensor (NOUT) signal.
By comparing the signals indicating the secondary pulley revolution (speed) and output shaft revolution (speed), the TCM judges if the shift mode is belt mode or not.

When the TCM requests the shift mode to be changed to belt mode, if the difference between the transmission revolution sensor (NSS) and (NOUT) signals is more than 300 rpm, it determines the shift solenoid valve SL2 is malfunctioning, illuminates the MIL and stores this DTC.

Under normal conditions, when the TCM requests the shift mode to be changed to gear mode, line pressure is applied from the shift solenoid SL1 to engage the C1 clutch and gear mode is entered.

When the shift solenoid valve SL2 is stuck ON, if the TCM requests the shift mode to be changed to gear mode, line pressure is applied to the clutch apply control valve from the shift solenoid valve SL2 and in turn line pressure to the C1 clutch is blocked.

As a result, the C1 clutch cannot be engaged and the shift mode cannot be changed.

In this case, when the TCM requests the shift mode to be changed to gear mode, it detects that gear mode cannot be entered (the C1 clutch is not engaged and the difference between the transmission revolution sensor (NT) signal and transmission revolution sensor (NC1) signal exceeds the threshold) and determines that the shift solenoid valve SL2 is stuck ON, illuminates the MIL and stores a DTC.

SL2 Stuck ON Detection Condition:

*A	TCM commands C1 clutch engagement when shift solenoid valve SL2 normal	*B	TCM commands C1 clutch engagement when shift solenoid valve SL2 stuck ON
*1	Shift Solenoid Valve SL1	*2	Shift Solenoid Valve SL2
*3	Clutch Apply Control Valve	*4	C1 Clutch
*a	Shift solenoid valve SL2 stuck ON	-	-
	Oil Pressure Flow		Valve Movement

MONITOR STRATEGY

Related DTCs	P0776: Pressure control solenoid "B" (Shift solenoid valve SL2)/Functional check
Required sensors/Components	Crankshaft position sensor Transmission revolution sensor (NT) Transmission revolution sensor (NC1) Transmission revolution sensor (NSS) Transmission revolution sensor (NOUT) CVT fluid temperature sensor Engine coolant temperature sensor Oil pressure sensor Shift solenoid valve SL1 Shift solenoid valve SL2 Shift solenoid valve SLP Shift solenoid valve SLS
Frequency of operation	Continuous
Duration	OFF malfunction (A): 2 sec. OFF malfunction (B): - OFF malfunction (C): 1 sec. ON malfunction (A): 1 sec. ON malfunction (B): 2 sec. ON malfunction (C): 1 sec.
MIL operation	2 driving cycles
Sequence of operation	None

TYPICAL ENABLING CONDITIONS

All

ETC system

(Electronic throttle control system)

Not system down

(MIL illuminated by following codes: P0121, P0122, P0123, P0222, P0223, P0604, P0606, P0607, P060D, P060E, P0657, P0658, P1607, P16B0, P2102, P2103, P2111, P2112, P2119, P2135)

KCS sensor circuit

(Knock sensor)

Not circuit malfunction

(MIL illuminated by following codes: P0327, P0328)

ECT sensor circuit

(Engine coolant temperature sensor)

Not circuit malfunction

(MIL illuminated by following codes: P0117, P0118)

IAT sensor circuit

(Intake air temperature sensor)

Not circuit malfunction

(MIL illuminated by following codes: P0112, P0113)

Crankshaft position sensor "A" circuit

(Crankshaft position sensor)

Not circuit malfunction

(MIL illuminated by following codes: P0335, P0337, P0338)

CAN communication between ECM and TCM

Not system down

(MIL illuminated by following codes: U0100, U0101)

Low voltage flag

OFF

Pressure control solenoid "J" circuit

(Shift solenoid valve SLP)

Not circuit malfunction

(MIL illuminated by following codes: P2826, P2827)

Pressure control solenoid "K" circuit

(Shift solenoid valve SLS)

Not circuit malfunction

(MIL illuminated by following codes: P282F, P2830)

Pressure control solenoid "A" circuit

(Shift solenoid valve SL1)

Not circuit malfunction

(MIL illuminated by following codes: P0962, P0963)

Pressure control solenoid "B" circuit

(Shift solenoid valve SL2)

Not circuit malfunction

(MIL illuminated by following codes: P0966, P0967)

Turbine speed sensor "A" circuit

(Transmission revolution sensor (NT))

Not circuit malfunction

(MIL illuminated by following codes: P0717, P07BF, P07C0)

Intermediate shaft speed sensor "C" circuit

(Transmission revolution sensor (NSS))

Not circuit malfunction

(MIL illuminated by following codes: P07C9, P07CA, P2751)

Gear shift position circuit

Not circuit malfunction

(MIL illuminated by following codes: P0916, P0917)

Output speed sensor circuit

(Transmission revolution sensor (NOUT))

Not circuit malfunction

(MIL illuminated by following codes: P0722, P077C, P077D)

Intermediate shaft speed sensor "B" circuit

(Transmission revolution sensor (NC1))

Not circuit malfunction

(MIL illuminated by following codes: P07C7, P07C8, P2747)

Engine

Starting

OFF malfunction (A)

Shift solenoid valve SLP	Operating shift control by TCM command
Engine speed	500 rpm or more
Secondary sheave speed	More than 0 rpm
Any of the following conditions are met: (a) or (b)	-
(a) Output speed	More than 0 rpm
(b) All of the following conditions are met	-
- Output speed	0 rpm
- Gear mode clutch speed	0 rpm
- Synchronizer	Engaged

OFF malfunction (B)

Shift solenoid valve SLP	Operating shift control by TCM command
Engine speed	500 rpm or more
Synchronizer	Engaged
Turbine torque	40 Nm (408 kgfcm, 30 ft.*lbf) or more
Accelerator pedal release flag	OFF

OFF malfunction (C)

Engine speed	500 rpm or more
Shift position	"D" or "B"
Secondary sheave torque	40 Nm (408 kgfcm, 30 ft.*lbf) or more
Accelerator pedal release flag	OFF
Output speed	More than 80 rpm

ON malfunction (A)

Shift solenoid valve SLP	Operating shift control by TCM command
Engine speed	500 rpm or more
Synchronizer	Engaged
Turbine speed	More than 0 rpm
Any of the following conditions are met: (a) or (b)	-
(a) Gear mode clutch speed	More than 0 rpm
(b) All of the following conditions are met	-
- Gear mode clutch speed	0 rpm
- Output speed	0 rpm

ON malfunction (B)

Engine speed	550 rpm or more
Transmission fluid temperature	-10°C (14°F) or more
Time after following condition is met	0.5 sec. or more
- Variation of the accelerator pedal angle (within 32.768 msec.)	Less than 0.5%
Shift solenoid valve SLS	Operating clamping pressure control by TCM command
ECT	60°C (140°F) or more
Spark advance from MAX. retard timing by KCS control	0 °CA or more
Gear and belt mode clutch	Either engagement or disengagement

ON malfunction (C)

Shift solenoid valve SLP	Operating shift control by TCM command
Engine speed	500 rpm or more
Secondary sheave torque	40 Nm (408 kgfcm, 30 ft.*lbf) or more
Accelerator pedal release flag	OFF

TYPICAL MALFUNCTION THRESHOLDS

OFF malfunction

Any of the following conditions are met: OFF malfunction (A) and (B) or (A) and (C)

OFF malfunction (A)

TCM indicate belt mode clutch	Engagement
Secondary sheave speed - Output speed	More than 300 rpm

OFF malfunction (B) (after OFF malfunction (A) is met)

TCM indicate gear mode clutch	Engagement
Turbine Speed - Gear mode clutch speed	Less than 25 rpm

OFF malfunction (C) (after OFF malfunction (A) is met)

Shift solenoid valve SLP	Operating belt mode clutch control by TCM command
Secondary sheave speed - Output speed	Less than 25 rpm

ON malfunction

All of the following conditions are met: ON malfunction (A), (B) and (C)

ON malfunction (A)

TCM indicate gear mode clutch	Engagement
Turbine speed - Gear mode clutch speed	More than 200 rpm

ON malfunction (B) (after ON malfunction (A) is met)

Target clamping pressure	1.4 MPa (14.3 kgf/cm², 203 psi) or more
Actual clamping pressure - Target clamping pressure	Less than 0.5 MPa (5.1 kgf/cm², 73 psi)

ON malfunction (C) (after ON malfunction (A) and (B) are met)

TCM indicate belt mode clutch	Engagement
Secondary sheave speed - Output speed	Less than 25 rpm

CONFIRMATION DRIVING PATTERN

CAUTION:

When performing the confirmation driving pattern, obey all speed limits and traffic laws.

HINT:

After repairs have been completed, clear the DTCs and then check that the vehicle has returned to normal by performing the following All Readiness check procedure.
When clearing the permanent DTCs, refer to the Clear Permanent DTC procedure.
Click here

Connect the Techstream to the DLC3.
Turn the engine switch on (IG) and turn the Techstream on.
Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
Turn the engine switch off and wait for 2 minutes or more.
Turn the engine switch on (IG) and turn the Techstream on.
Start the engine.
Perform the D Position Shift Test inspection in Road Test. [*1]
Click here

HINT:

[*1]: Normal judgment procedure.

The normal judgment procedure is used to complete DTC judgment and also used when clearing permanent DTCs.
Stop the vehicle.
Enter the following menus: Powertrain / Transmission / Utility / All Readiness.
Input the DTC: P07757F.

Check the DTC judgment result.

Techstream Display	Description
NORMAL	DTC judgment completed System normal
ABNORMAL	DTC judgment completed System abnormal
INCOMPLETE	DTC judgment not completed Perform driving pattern after confirming DTC enabling conditions
N/A	Unable to perform DTC judgment Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit

HINT:

If the judgment result shows NORMAL, the system is normal.
If the judgment result shows ABNORMAL, the system has a malfunction.
If the judgment result shows INCOMPLETE or N/A, perform the normal judgment procedure again.

CAUTION / NOTICE / HINT

NOTICE:

Perform the universal trip to clear permanent DTCs.
Click here
Perform registration and/or initialization when parts related to the continuously variable transaxle system are replaced.
Click here
Check that no DTCs are stored after performing initialization.
Click here

HINT:

If any DTCs other than P07757F are output, perform troubleshooting for those DTCs first.

PROCEDURE

1.	CHECK DTC OUTPUT (IN ADDITION TO DTC P07757F)

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(d) Enter the following menus: Powertrain / Transmission / Trouble Codes.

Powertrain > Transmission > Trouble Codes

(e) Read the DTCs using the Techstream.

HINT:

If DTC P077512 or P077514 is output, perform troubleshooting for that DTC first.
If DTCs P077512 and P077514 are not output but DTC P281F00 is output, perform troubleshooting for DTC P281F00 first.

Result	Proceed to
Only DTC P07757F is output	A
DTC P07457F and P07757F are output	B
DTC P07757F and P077512 are output	C
DTC P07757F and P077514 are output	D
DTC P07757F and P281F00 are output	E
DTC P07757F and DTCs other than P07457F, P077512, P077514 and P281F00 are output	F

GO TO STEP 5

GO TO DTC CHART (DTC P077512)

GO TO DTC CHART (DTC P077514)

GO TO DTC CHART (DTC P281F00)

GO TO DTC CHART

2.	INSPECT TRANSMISSION VALVE BODY ASSEMBLY (SHIFT SOLENOID VALVE SL2)

(a) Disconnect the transmission wire connector from the shift solenoid valve SL2.

Click here

Transmission Valve Body Assembly

Shift Solenoid Valve SL2

Component without harness connected

(Shift Solenoid Valve SL2)

(b) Connect a positive (+) lead from the battery with a 21 W bulb to terminal 1 and a negative (-) lead to terminal 2 of the shift solenoid valve SL2 connector. Check that the valve moves and makes an operating sound.

OK:

Valve moves and makes an operating sound.

GO TO STEP 4

3.	REPLACE CONTINUOUSLY VARIABLE TRANSAXLE ASSEMBLY

(a) Replace the continuously variable transaxle assembly.

Click here

PERFORM REGISTRATION AND INITIALIZATION

for Registration: Click here

for Initialization: Click here

4.	REPLACE TRANSMISSION VALVE BODY ASSEMBLY

(a) Replace the transmission valve body assembly.

Click here

PERFORM REGISTRATION AND INITIALIZATION

for Registration: Click here

for Initialization: Click here

5.	INSPECT TRANSMISSION VALVE BODY ASSEMBLY (SHIFT SOLENOID VALVE SL1)

(a) Disconnect the transmission wire connector from the shift solenoid valve SL1.

Click here

Transmission Valve Body Assembly

Shift Solenoid Valve SL1

Component without harness connected

(Shift Solenoid Valve SL1)

(b) Connect a positive (+) lead from the battery with a 21 W bulb to terminal 1 and a negative (-) lead to terminal 2 of the shift solenoid valve SL1 connector. Check that the valve moves and makes an operating sound.

OK:

Valve moves and makes an operating sound.

GO TO STEP 2

6.	REPLACE TRANSMISSION VALVE BODY ASSEMBLY

(a) Replace the transmission valve body assembly.

Click here

PERFORM REGISTRATION AND INITIALIZATION

for Registration: Click here

for Initialization: Click here