Code No.P0781: 1-2 shift valve system

OPERATION

The 1-2 shift valve is operated by the hydraulic pressure, and the shift change is performed between the 1st gear and 2nd gear.

DIAGNOSIS CODE SET CONDITIONS

While the engine is running, when the fluid temperature is 20°C or more, the engine coolant temperature is 40°C or more, the drive mode selector position is in other than 4L/4LLc, and the mode is in other than sport mode (1st/2nd/3rd), if a status is detected with which the gear ratio (2nd/4th/5th) does not change according to the shift pattern due to the return spring seizure of 1-2 shift valve (return spring is kept compressed and does not return) (2 drive cycle), code No.P0781 is set.

note

When the seizure of 1-2 shift valve return spring is detected, the normal gear ratio cannot be obtained because the gear does not change as shown in the table when the gear is in 2nd/4th/5th.

Shift range (gear ratio)	Shift range (gear ratio) at return spring seizure
1st (3.520)	1st (3.520)
2nd (2.042)	1st (3.520)
3rd (1.400)	3rd (1.400)
4th (1.000)	3rd (1.400)
5th (0.716)	Neutral

PROBABLE CAUSES

Malfunction of 1-2 shift valve (seizure of spring compression side)
Malfunction of the A/T-ECU

DIAGNOSIS PROCEDURE

STEP 1. 1-2 shift valve check

Remove the valve body, and check the 1-2 shift valve and return spring for damage and any faults.

Q. Is the check result normal?

	Go to Step 2.

	Replace the 1-2 shift valve and return spring.

STEP 2. Check whether the diagnosis code is set again.

Check again if the diagnosis code is set.

Q. Is code No.P0781 set?

	Replace the A/T-ECU.

	Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).