Code No.P1779: 1st Gear Incorrect Ratio (Engine Brake)

OPERATION

The ECU detects the current gear/speed according to the output signals from the input and output shaft speed sensor.

DIAGNOSIS CODE SET CONDITIONS

If the output shaft speed sensor output value deviates from the input shaft speed sensor output value, which is multiplied by the 1st gear ratio, by a predetermined range or more after the gear shifting, diagnosis code No. P1779 is set.

PROBABLE CAUSES

Damaged harness wires and connectors
Malfunction of the A/T-ECU
Malfunction of solenoid valve
Malfunction of the valve body assembly
Malfunction of the input shaft speed sensor system (for diagnosis codes P0717, P07BF, P07C0)
Malfunction of the output shaft speed sensor system (for diagnosis codes P0722, P077C, P077D)
Malfunction of the line pressure control solenoid system (for diagnosis codes P0961, P0962, P0963)
Malfunction of the pressure control solenoid SL1 system (for diagnosis codes P0965, P0966, P0967)
Malfunction of the pressure control solenoid SL2 system (for diagnosis codes P0969, P0970, P0971)
Malfunction of the pressure control solenoid SL3 system (for diagnosis codes P2719, P2720, P2721)
Malfunction of the pressure control solenoid SL4 system (for diagnosis codes P2728, P2729, P2730)
Malfunction of the pressure control solenoid SL5 system (for diagnosis codes P2737, P2738, P2739)
Malfunction of the shift solenoid SR system (for diagnosis codes P0973, P0974)
Malfunction of the shift solenoid SB system (for diagnosis codes P0976, P0977)

DIAGNOSIS PROCEDURE

STEP 1. Time lag test

Refer to

Q. Is the check result normal?

	Go to Step 2.

	Go to Step 4.

STEP 2. Torque converter stall check

Refer to

Q. Is the check result normal?

	Go to Step 3.

	Go to Step 4.

STEP 3. Hydraulic pressure test

Refer to

Q. Is the check result normal?

	Go to Step 5.

	Go to Step 4.

STEP 4. Solenoid check

Check the line pressure control solenoid, the pressure control solenoid SL1, SL3, SL4, SL5 and the shift solenoid SR, SB (Refer to

Q. Is the check result normal?

	Replace the transmission assembly.

	Replace the valve body assembly.

STEP 5. Check whether the diagnosis code is set again.

Ignition switch: "LOCK"(OFF) → "ON"
Check again if the diagnosis code is set.

Q. Is diagnosis code No.P1779 set?

	Go to Step 6.

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

STEP 6. After replace the valve body assembly, check whether the diagnosis code is set again.

Ignition switch: "LOCK"(OFF) → "ON"
Check again if the diagnosis code is set.

Q. Is diagnosis code No.P1779 set?

	Replace the transmission assembly.

	The procedure is complete.