P0781
A761E AUTOMATIC TRANSMISSION: AUTOMATIC TRANSMISSION SYSTEM: P0781: 1-2 Shift (1-2 Shift Valve)
DTC P0781 - 1-2 Shift (1-2 Shift Valve)
DESCRIPTION
The 1-2 shift valve performs shifting to 1st gear and other gears.
HINT:
- Gear positions in the event of a solenoid valve mechanical problem:
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.
HINT: 1st*: Under engine braking, downshifting to 1st or 2nd gear is prohibited.
MONITOR DESCRIPTION
This DTC indicates that the 1-2 shift valve in the valve body is locked in the direction the spring is compressed.
The ECM commands gear shifts by turning the shift solenoid valves "ON/OFF" and switching oil pressure to the valves in the valve body.
The ECM calculates the "actual" transmission gear by comparing the signals from the input speed sensor (NT) and the output speed sensor (SP2). The ECM can detect many mechanical problems in the shift solenoids, valve body, and the transmission clutches, brakes, and gears. If the ECM detects that the actual gear position and the commanded gear position are different, it will illuminate the MIL and store the DTC.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
All
Condition (A)
Condition (B)
Condition (C)
Condition (D)
TYPICAL MALFUNCTION THRESHOLDS
- Both of the following conditions are met: Condition (A), and Condition (B), (C) or (D)
Condition (A)
Condition (B)
Condition (C)
Condition (D)
INSPECTION PROCEDURE
PROCEDURE
1. CHECK OTHER DTCS OUTPUT (IN ADDITION TO DTC P0781)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
(e) Read the DTCs using the Techstream.
Result:
HINT: If any other codes besides P0781 are output, perform troubleshooting for those DTCs first.
B -- GO TO DTC CHART
A -- Continue to next step.
2. PERFORM ACTIVE TEST USING TECHSTREAM (RUNNING TEST)
HINT: Using the Techstream to perform Active Tests allows relays, VSVs, actuators and other items to be operated without removing any parts. This non-intrusive functional inspection can be very useful because intermittent operation may be discovered before parts or wiring is disturbed. Performing Active Tests early in troubleshooting is one way to save diagnostic time. Data List information can be displayed while performing Active Tests.
(a) Warm up the engine.
(b) Turn the ignition switch OFF.
(c) Connect the Techstream to the DLC3.
(d) Turn the ignition switch to ON.
(e) Turn the Techstream on.
(f) Enter the following menus: Powertrain / Engine and ECT / Active Test.
(g) Perform the Active Test using the Techstream.
HINT: While driving, the shift position can be forcibly changed with the Techstream.
Comparing the shift position commanded by the Active Test with the actual shift position enables you to confirm the problem Fail-Safe Chart.
Engine and ECT
HINT:
- This test can be conducted when the vehicle speed is 50 km/h (31 mph) or less.
- The 4th -> 5th and 5th -> 6th up-shifts must be performed with the accelerator pedal released.
- The 6th -> 5th and 5th -> 4th down-shifts 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 display on the Techstream.
- Gear positions in the event of a solenoid valve mechanical problem:
N*: Neutral
OK:
Gear position changes in accordance with the Techstream command.
NG -- REPAIR OR REPLACE TRANSMISSION VALVE BODY ASSEMBLY
OK -- Continue to next step.
3. PERFORM ACTIVE TEST USING TECHSTREAM (SHIFT SOLENOID VALVE SLT)
NOTICE:
- Perform the test at the normal operating ATF temperature: 50 to 80°C (122 to 176°F).
- Be careful to prevent SST's hose from interfering with the exhaust pipe.
- Perform the test with the A/C OFF.
HINT: Using the Techstream to perform Active Tests allows relays, VSVs, actuators and other items to be operated without removing any parts. This non-intrusive functional inspection can be very useful because intermittent operation may be discovered before parts or wiring is disturbed. Performing Active Tests early in troubleshooting is one way to save diagnostic time. Data List information can be displayed while performing Active Tests.
(a) Remove the test plug on the transmission case center right side and connect SST.
SST: 09992-00095
09992-00231
09992-00271
(b) Connect the Techstream to the DLC3.
(c) Start the engine and warm it up.
(d) Measure the line pressure with SST.
(e) Turn the Techstream on.
(f) Enter the following menus: Powertrain / Engine and ECT / Active Test.
(g) According to the display on the Techstream, perform the Active Test.
(h) Measure the line pressure with SST.
Engine and ECT
HINT:
- *: Control the Line Pressure Up in the Active Test is performed to check the line pressure change by connecting SST to the automatic transmission, which is used in the Hydraulic Test Hydraulic Test.
- The pressure values in the Active Test and Hydraulic Test are different from each other.
- Normally, the line pressure detected in the Active Test is approximately half of the value detected in the Hydraulic Test's stall test.
OK:
The line pressure changes as specified when performing the Active Test.
NG -- REPLACE SHIFT SOLENOID VALVE SLT
OK -- Continue to next step.
4. CLEAR THE DTC AND PERFORM THE RUNNING TEST
(a) Clear the DTC, and check for DTCs again after conducting the "MONITOR DRIVE PATTERN FOR ECT TEST" Monitors, Trips, Drive Cycles and Readiness Codes.
OK:
No DTC code is output
NG -- REPAIR OR REPLACE TRANSMISSION VALVE BODY ASSEMBLY
OK -- END