System Description

WARNING: This page is about a different car, the 2017 Lexus RC 350, 2017 Lexus RC 300, 2016 Lexus RC 350, 2016 Lexus RC 300, and 2015 Lexus RC 350. However, it is still accessible from the selected car via links, so may be relevant.

The 1-2 shift valve performs shifting to 1st gear and other gears.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	MIL	Memory
P0781	1-2 Shift (1-2 Shift Valve)	1. Diagnosis Condition 2. Malfunction Status 3. Malfunction Time 4. Other DTC Detection Condition 1 Engine coolant temperature is 40°C (104°F) or more and the vehicle is driven with the shift lever in D (no malfunctions are detected in the shift solenoid valve S1, S2, S3, S4, SR, SL1 and SL2, transmission revolution sensors (NT, SP2), coolant temperature sensor, knock control sensor, electronic throttle). Both of the following conditions (a) and (b) are met: When the ECM commands the transmission to shift to 2nd gear, the actual gear is shifted to 1st. When the ECM commands the transmission to shift to 4th gear, the actual gear is shifted to 3rd. 0.4 seconds 2-trip detection logic DTC Detection Condition 2 Engine coolant temperature is 40°C (104°F) or more and the vehicle is driven with the shift lever in D (no malfunctions are detected in the shift solenoid valve S1, S2, S3, S4, SR, SL1 and SL2, transmission revolution sensors (NT, SP2), coolant temperature sensor, knock control sensor, electronic throttle). Both of the following conditions (a) and (b) are met: When the ECM commands the transmission to shift to 2nd gear, the actual gear is shifted to 1st. When the ECM commands the transmission to shift to 5th gear, the engine overruns (clutch slips). 0.4 seconds or more 2-trip detection logic	Shift solenoid valve SLT remains open or closed Transmission valve body assembly is blocked or stuck (1-2 shift valve) Automatic transmission with transfer assembly (clutch, brake, gear, etc.)	Comes on	DTC stored

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

MIL

Memory

P0781

1-2 Shift (1-2 Shift Valve)

1. Diagnosis Condition 2. Malfunction Status 3. Malfunction Time 4. Other

DTC Detection Condition 1

Engine coolant temperature is 40°C (104°F) or more and the vehicle is driven with the shift lever in D (no malfunctions are detected in the shift solenoid valve S1, S2, S3, S4, SR, SL1 and SL2, transmission revolution sensors (NT, SP2), coolant temperature sensor, knock control sensor, electronic throttle).
Both of the following conditions (a) and (b) are met:
1. When the ECM commands the transmission to shift to 2nd gear, the actual gear is shifted to 1st.
2. When the ECM commands the transmission to shift to 4th gear, the actual gear is shifted to 3rd.
0.4 seconds
2-trip detection logic

DTC Detection Condition 2

Engine coolant temperature is 40°C (104°F) or more and the vehicle is driven with the shift lever in D (no malfunctions are detected in the shift solenoid valve S1, S2, S3, S4, SR, SL1 and SL2, transmission revolution sensors (NT, SP2), coolant temperature sensor, knock control sensor, electronic throttle).
Both of the following conditions (a) and (b) are met:
1. When the ECM commands the transmission to shift to 2nd gear, the actual gear is shifted to 1st.
2. When the ECM commands the transmission to shift to 5th gear, the engine overruns (clutch slips).
0.4 seconds or more
2-trip detection logic

Shift solenoid valve SLT remains open or closed
Transmission valve body assembly is blocked or stuck (1-2 shift valve)
Automatic transmission with transfer assembly (clutch, brake, gear, etc.)

Comes on

DTC stored

HINT:

Gear positions in the event of a solenoid valve mechanical problem:

ECM command gearshift	1st	2nd	3rd	4th	5th	6th
Actual gear position under malfunction	1st	1st	3rd	3rd	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 conditions	1st	2nd	3rd	4th	5th	6th
Actual gear position under fail-safe mode	1st (*1)	1st (*1)	3rd	3rd	3rd	3rd

*1: Under engine braking, downshifting to 1st or 2nd gear is prohibited.