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Home >> Lexus >> 2006 >> IS 250 RWD, Standard >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 2 (Automatic Transmission (A960E)) >> Automatic Transmission System >> DTC P0756 Shift Solenoid "B" Performance (Shift Solenoid Valve S2) >> System Description

System Description

WARNING: This page is about a different variant/trim than selected.

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 DETECTION CONDITION CHART

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)
  1. When the ECM directs the gearshift to switch to 5th gear, the actual gear is shifted to 6th.
  2. 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)
  1. When the ECM directs the gearshift to switch to 1st gear, the actual gear is shifted to 3rd.
  2. 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:

ECM COMMAND GEARSHIFT CHART

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