LEMON Manuals: Even more car manuals for everyone
Home >> Lexus >> 2006 >> IS 250 RWD, Standard >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 2 (Automatic Transmission (A960E)) >> Automatic Transmission System >> DTC P0751 Shift Solenoid "A" Performance (Shift Solenoid Valve S1) >> 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
P0751 S1 stuck ON malfunction*1:
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 2nd.
  2. When the ECM directs the gearshift to switch to 5th gear, the actual gear is also shifted to 5th.
  • Shift solenoid valve S1 remains open
  • Valve body is blocked
  • Automatic transmission (clutch, brake or gear, etc.)
  S1 stuck OFF malfunction*2:
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 2nd gear, the actual gear is shifted to 1st.
  2. When the ECM directs the gearshift to switch to 5th gear, the actual gear is also shifted to 5th.
  • Shift solenoid valve S1 remains closed
  • Shift solenoid valve SLT remains open or closed
  • Valve body is blocked
  • No.2 brake malfunction (Driving is difficult.)
  • Automatic transmission (clutch, brake or gear, etc.)

HINT:

GEAR POSITION DURING FAIL-SAFE OPERATION

Gear position under normal conditions 1st 2nd 3rd 4th 5th 6th
*1: Actual gear position under fail safe mode when S1 stuck ON malfunction 2nd 2nd        
*2: Actual gear position under fail safe mode when S1 stuck OFF malfunction 1st(1) 1st(1)   3rd 3rd 3rd
(1) Under engine braking downshifting to 1st or 2nd gear is prohibited.