System Description

WARNING: This page is about a different car, the 2010 Lexus IS 250. However, it is still accessible from the selected car via links, so may be relevant.

The ECM uses signals from the output shaft speed sensor and input speed sensor to detect the actual gear position (1st, 2nd, 3rd, 4th, 5th or 6th gear).

Then the ECM compares the actual gear with the shift schedule in the ECM memory to detect mechanical problems of the shift solenoid valves, valve body or automatic transmission (clutch, brake or gear, etc.).

DTC No.	DTC Detection Condition	Trouble Area
P0756	S2 stuck ON malfunction^*1 : Shifting to 3rd and 5th gears is impossible. The ECM determines there is a malfunction when the following conditions are both met. (2-trip detection logic) When the ECM directs the gearshift to switch to 5th gear, the actual gear is shifted to 6th. When the ECM directs the gearshift to switch to 6th gear, the actual gear is shifted to 6th.	Shift solenoid valve S2 remains open Valve body is blocked Automatic transmission (clutch, brake or gear, etc.)
↑	S2 stuck OFF malfunction^*2 : The vehicle starts in 3rd gear and shifting to 6th gear is impossible. The ECM determines there is a malfunction when the following conditions are both met. (2-trip detection logic) When the ECM directs the gearshift to switch to 1st gear, the actual gear is shifted to 3rd. When the ECM directs the gearshift to switch to 6th gear, the actual gear is shifted to 5th.	Shift solenoid valve S2 remains closed Valve body is blocked Automatic transmission (clutch, brake or gear, etc.)

HINT:

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

ECM command gearshift	1st	2nd	3rd	4th	5th	6th
*1: Actual gear position under S2 stuck ON malfunction	↑	↑	2nd	↑	6th	↑
*2: Actual gear position under S2 stuck OFF malfunction	3rd	3rd	3rd	↑	5th	5th