Dtc P0751 Shift Solenoid A Performance (Shift Solenoid Valve S1)

Lexus IS250 IS220d GSE20 ALE20 - A960E AUTOMATIC TRANSMISSION

SYSTEM DESCRIPTION

MONITOR DESCRIPTION

INSPECTION PROCEDURE

CHECK OTHER DTCS OUTPUT (IN ADDITION TO DTC P0751)

PERFORM ACTIVE TEST BY INTELLIGENT TESTER (SHIFT SOLENOID VALVE SLT)

INSPECT SHIFT SOLENOID VALVE S1

INSPECT TRANSMISSION VALVE BODY ASSEMBLY

DTC P0751 Shift Solenoid "A" Performance (Shift Solenoid Valve S1)

SYSTEM DESCRIPTION

The ECM uses signals from the output shaft speed sensor and input speed sensor to detect the actual gear position (1st, 2nd, 3rd, 4th, 5th or 6th gear).


Then the ECM compares the actual gear with the shift schedule in the ECM memory to detect mechanical problems of the shift solenoid valves, valve body or automatic transmission (clutch, brake or gear, etc.).

DTC No.DTC Detection ConditionTrouble Area
P0751
S1 stuck ON malfunction*1:
The ECM determines there is a malfunction when the following conditions are both met. (2-trip detection logic)
When the ECM directs the gearshift to switch to 1st gear, the actual gear is shifted to 2nd.
When the ECM directs the gearshift to switch to 5th gear, the actual gear is also shifted to 5th.
Shift solenoid valve S1 remains open
Valve body is blocked
Automatic transmission (clutch, brake or gear, etc.)
↑
S1 stuck OFF malfunction*2:
The ECM determines there is a malfunction when the following conditions are both met.(2-trip detection logic)
When the ECM directs the gearshift to switch to 2nd gear, the actual gear is shifted to 1st.
When the ECM directs the gearshift to switch to 5th gear, the actual gear is also shifted to 5th.
Shift solenoid valve S1 remains closed
Shift solenoid valve SLT remains open or closed
Valve body is blocked
No. 2 brake malfunction (Driving is difficult.)
Automatic transmission (clutch, brake or gear, etc.)
  • HINT:
Gear positions in the event of a solenoid valve mechanical problem:
ECM command gearshift1st2nd3rd4th5th6th
*1: Actual gear position under S1 stuck ON malfunction2nd2nd↑↑↑↑
*2: Actual gear position under S1 stuck OFF malfunction1st1st↑↑↑N*
N*: Neutral
Gear position during fail-safe operation:
If any malfunction is detected, the ECM changes into the fail-safe mode to shift into the gear positions as shown in the table below.
Gear position under normal conditions1st2nd3rd4th5th6th
*1: Actual gear position under fail safe mode when S1 stuck ON malfunction2nd2nd↑↑↑↑
*2: Actual gear position under fail safe mode when S1 stuck OFF malfunction1st*3 1st*3 ↑3rd3rd3rd
*3: Under engine braking downshifting to 1st or 2nd gear is prohibited.

MONITOR DESCRIPTION

This DTC indicates "stuck ON malfunction" or "stuck OFF malfunction" of the shift solenoid valve S1.


The ECM commands gear shifts by turning the shift solenoid valves "ON/OFF". When the gear position commanded by the ECM and the actual gear position are not the same, the ECM illuminates the MIL and stores the DTC.


INSPECTION PROCEDURE

ACTIVE TEST
  • HINT:
  • Performing the intelligent tester Active Test allows relay, Vacuum Switching Valve (VSV), actuator and other items to be operated without removing any parts. Performing the Active Test early in troubleshooting is one way to shorten labor time.
  • The Data List can be displayed during the Active Test.

Warm up the engine.

Turn the engine switch off.

Connect the intelligent tester to the DLC3.

Turn the engine switch on (IG) position.

Turn on the tester.

Select the item "Enter / Powertrain / ECT / Active Test".

Follow the instructions on the tester and read the Active Test.

  • HINT:
  • While driving, the shift position can be forcibly changed with the intelligent tester.
  • Comparing the shift position commanded by the ACTIVE TEST with the actual shift position enables you to confirm the problem .
ItemTest DetailsDiagnostic Note
Control Shift Position [Test Details]
Operate the shift solenoid valve and set each shift position by yourself.
[Vehicle Condition]
IDL: ON (4th, 5th and 6th)
Less than 50 km/h (31 mph)
[Others]
Press "→" button: Shift up
Press "←" button: Shift down
 Possible to check the operation of the shift solenoid valves.
  • HINT:
This test can be conducted when the vehicle speed is 50 km/h (31 mph) or less.
The 4th to 5th and 5th to 6th up-shiftings must be performed with the accelerator pedal released.
The 6th to 5th and 5th to 4th down-shiftings must be performed with the accelerator pedal released.
Do not operate the accelerator pedal for at least 2 seconds after shifting and do not shift successively.
The shift position commanded by the ECM is shown in the DATA LIST (Shift Status) display on the intelligent tester.
The shift solenoid valve S1 is turned on/off normally when the shift lever is in the D position:
ECM command gearshift1st2nd3rd4th5th6th
Shift solenoid valve S1OFFONONONONON
1.CHECK OTHER DTCS OUTPUT (IN ADDITION TO DTC P0751)

Connect the intelligent tester to the DLC3.

Turn the engine switch on (IG) position.

Turn on the tester.

Select the item "Powertrain / ECT / DTC / Current or Pending".

Read the DTCs using the intelligent tester.

  • Result:
  • Display (DTC output)Proceed to
    Only "P0751" is outputA
    "P0751" and other DTCsB
  • HINT:
  • If any other codes besides "P0751" are output, perform troubleshooting for those DTCs first.
B
GO TO DTC CHART
A
2.PERFORM ACTIVE TEST BY INTELLIGENT TESTER (SHIFT SOLENOID VALVE SLT)
  • NOTICE:
Perform the test at the normal operating ATF (Automatic Transmission Fluid) temperature: 50 to 80°C (122 to 176°F)
Be careful to prevent SST hose from interfering with the exhaust pipe.
This check must be conducted after checking and adjusting engine.
Perform under condition that A/C is OFF.
  • HINT:
  • Performing the intelligent tester Active Test allows relay, Vacuum Switching Valve (VSV), actuator and other items to be operated without removing any parts. Performing the Active Test early in troubleshooting is one way to shorten labor time.
  • The Data List can be displayed during the Active Test.

Turn the engine switch off.

Lift the vehicle up.

Dtc P0751 Shift Solenoid A Performance (Shift Solenoid Valve S1). A960E AUTOMATIC TRANSMISSION. Lexus IS250 IS220d GSE20 ALE20

Remove the test plug on the transmission case center right side and connect SST.

  • SST
  • 09992-00095(09992-00231,09992-00271)

Lower the vehicle.

Fully apply the parking brake and chock the 4 wheels.

Connect the intelligent tester to the DLC3.

Start the engine.

Warm up the ATF (Automatic Transmission Fluid).

Measure the line pressure when the engine is idling.

Turn on the intelligent tester.

Select the item "Enter / Powertrain / ECT / Active Test".

Follow the instructions on the tester and perform the Active Test.

Measure the line pressure with SST.

ItemTest Details
Activate the Solenoid (SLT)*[Test Details]
Operate the shift solenoid SLT and raise the line pressure.
[Vehicle Condition]
Vehicle Stopped.
IDL: ON
  • HINT:
  • OFF: Line pressure up (When the active test of "Activate the Solenoid (SLT)" is performed, the ECM commands the SLT solenoid to turn off).
  • ON: No action (normal operation)

*: "Activate the Solenoid (SLT)" in the ACTIVE TEST is performed to check the line pressure changes by connecting the SST to the automatic transmission, which is used in the HYDRAULIC TEST as well.

  • HINT:
  • The pressure values in ACTIVE TEST and HYDRAULIC TEST are different from each other.
  • OK:
  • The line pressure changes as specified when performing the ACTIVE TEST.
NG
REPLACE SHIFT SOLENOID VALVE SLT
OK
3.INSPECT SHIFT SOLENOID VALVE S1
Dtc P0751 Shift Solenoid A Performance (Shift Solenoid Valve S1). A960E AUTOMATIC TRANSMISSION. Lexus IS250 IS220d GSE20 ALE20

Remove the shift solenoid valve S1.

Measure the resistance according to the value(s) in the table below.

  • Standard resistance:
  • Tester ConnectionSpecified Condition
    20°C (68°F)
    Solenoid Connector (S1) - Solenoid Body (S1)11 to 15 Ω

Connect the positive (+) lead to the terminal of the solenoid connector, and the negative (-) lead to the solenoid body.

  • OK:
  • The solenoid makes an operating sound.
NG
REPLACE SHIFT SOLENOID VALVE S1
OK
4.INSPECT TRANSMISSION VALVE BODY ASSEMBLY
  • OK:
  • There are no foreign objects on each valve.
NG
REPLACE TRANSMISSION VALVE BODY ASSEMBLY
OK
REPLACE AUTOMATIC TRANSMISSION ASSEMBLY