DESCRIPTION The 1-2 shift
valve performs shifting to 1st gear and other gears. When shifting to
2nd and 4th gears is impossible, or when the ECM directs the
transmission to switch to 5th or 6th gear and the engine overruns
(clutch slips), this DTC is stored. |
DTC Code | DTC Detection Condition |
Trouble Area | | P0781 |
- Conditions (a) and (b), or (a) and (c) are met (2-trip detection logic):
(a) When the ECM directs the transmission to switch to 2nd gear, the actual gear is shifted to 1st.
(b) When the ECM directs the transmission to switch to 4th gear, the actual gear is shifted to 3rd.
(c) When the ECM directs the transmission to switch to 5th gear, the engine overruns (clutch slips). |
- Valve body is blocked or stuck (1-2 shift valve)
- Shift solenoid valve SLT remains open or closed
- Automatic transmission (clutch, brake, gear, etc.)
|
HINT:
| Gear position under normal conditions |
1st | 2nd |
3rd | 4th |
5th | 6th | |
Actual gear position under fail-safe mode |
1st* | 1st* |
3rd | 3rd |
3rd | 3rd |
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 compresses.
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, 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 |
Related DTCs | P0781: Valve body / Functional check | |
Required sensors/Components | Valve body, Automatic transmission assembly | |
Frequency of operation | Continuous | |
Duration | Condition (A) and (B) 0.4 seconds
Condition (C) 3 seconds Condition (D) 1 second | |
MIL operation | 2 driving cycles | |
Sequence of operation | None | TYPICAL ENABLING CONDITIONS All |
The monitor will run whenever the following DTCs are not present |
P0717 (Turbine speed sensor circuit) P0722 (Output Speed Sensor circuit)
P0710, P0712, P0713, P2740, P2742, P2743 (ATF temperature sensor circuit)
P0973, P0974 (Shift solenoid valve S1 circuit) P0976, P0977 (Shift solenoid valve S2 circuit)
P0979, P0980 (Shift solenoid valve S3 circuit) P0982, P0983 (Shift solenoid valve S4 circuit)
P0985, P0986 (Shift solenoid valve SR circuit) P0748 (Shift solenoid valve SL1 circuit)
P0778 (Shift solenoid valve SL2 circuit) P0115, P0116, P0117, P0118, P011B (ECT (Engine coolant temperature) sensor circuit)
P0327, P0328, P032C, P032D (KCS sensor circuit) | |
ETCS (Electric Throttle Control System) |
Not system down | | Transmission position |
"D" | | Duration time from shifting "N" to "D" |
4 seconds or more | | ECT |
40°C (104°F) or higher | | Spark advance from max. retard timing by KCS control |
0° crankshaft angle or more | |
Engine | Starting | Condition (A) |
ECM selected gear | 2nd | |
Vehicle speed | 2 km/h (1.2 mph) or more | |
Output speed | 2nd → 1st down-shift point or more | |
Throttle valve opening angle | 5% or more at 2000 rpm
(Conditions vary with engine speed) | |
Calculated load value | 7.75% or more (A/C off)
7.75% or more (A/C on) | | Input speed/output speed (NT/NO)
NT: Input (Turbine) speed NO: Internal counter shaft speed |
3.30 to 7.50 or 1.91 to 2.35 or 1.28 to 1.53
or 0.93 to 1.07 or 0.65 to 0.79 or
0.51 to 0.65 | Condition (B) |
ECM selected gear | 4th | |
Vehicle speed | 2 km/h (1.2 mph) or more | |
Throttle valve opening angle | 5% or more at 2000 rpm
(Conditions vary with engine speed) | |
Calculated load value | 7.75% or more (A/C off)
7.75% or more (A/C on) | | Input speed/output speed (NT/NO)
NT: Input (Turbine) speed NO: Internal counter shaft speed |
3.30 to 7.50 or 1.91 to 2.35 or 1.28 to 1.53
or 0.93 to 1.07 or 0.65 to 0.79 or
0.51 to 0.65 | Condition (C) |
Current ECM selected gear | 5th | |
Last ECM selected gear | 4th | |
Vehicle speed (During transition from 4th to 5th gear) |
Less than 100 km/h (62.2 mph) | Condition (D) |
ECM selected gear | 5th | |
Engine speed -Turbine speed (NE - NT) (After transition to 5th gear) |
150 rpm or less | | Vehicle speed (After transition to 5th gear) |
Less than 100 km/h (62.2 mph) | TYPICAL MALFUNCTION THRESHOLDS
- Both of the following conditions are met: Condition (A), and Condition (B), (C) or (D)
Condition (A) |
Turbine speed / Output speed (NT / NO) | 3.30 or more, and 7.50 or less
(This means actual gear is 1st) | Condition (B) |
Turbine speed / Output speed (NT / NO) | 1.28 or more, and 1.53 or less
(This means actual gear is 3rd) | Condition (C) |
Turbine speed - Output speed x 4th gear ratio (NT - NO x 4th gear ratio) |
1000 rpm or more | Condition (D) |
Turbine speed - Output speed x 5th gear ratio (NT - NO x 5th gear ratio) |
1000 rpm or more | CAUTION / NOTICE / HINT
NOTICE: Perform the universal trip to clear permanent DTCs (See page
 ). PROCEDURE
| 1. |
CHECK DTC 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 |
Result | Proceed to | |
Only P0781 is output |
A | | P0781 and other DTCs are output |
B | HINT: If any other codes besides P0781 are output, perform troubleshooting for those DTCs first.
| B |
 | GO TO DTC CHART |
|
A |
 | |
| 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) According to the display on the Techstream, perform the Active Test.
HINT: While driving, the shift position can be forcibly changed with the Techstream. Engine and ECT |
Tester Display | Test Part |
Control Range | Diagnostic Note | |
Control the Shift Position | Operate shift solenoid valves and set each shift position |
- Press "→" button: Shift up
- Press "←" button: Shift down
| Possible to check operation of the shift solenoid valves.
[Vehicle Condition] 50 km/h (30 mph) or less |
HINT:
| NG |
| REPAIR OR REPLACE TRANSMISSION VALVE BODY ASSEMBLY |
|
OK | |
| |
| 3. |
PERFORM ACTIVE TEST USING TECHSTREAM (SHIFT SOLENOID VALVE SLT) |
| NG | |
REPLACE SHIFT SOLENOID VALVE SLT |
|
OK | |
| |
| 4. |
CLEAR DTC AND PERFORM RUNNING TEST |
| OK | |
END |
| NG |
| REPAIR OR REPLACE AUTOMATIC TRANSMISSION ASSEMBLY | |
