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Home >> Lexus >> 2008 >> IS 250 RWD, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 22 (Automatic Transaxle) >> Automatic Transmission System >> DTC P0746: Pressure Control Solenoid "A" Performance (Shift Solenoid Valve SL1) >> System Description

System Description

WARNING: This page is about a different car, the 2008 Lexus IS F. However, it is still accessible from the selected car via links, so may be relevant.

The TCM detects the actual gear based on signals from the speed sensors (SP2, NC3 and NT)

Based on the detected gear and oil pressure switch output, the TCM detects related mechanical problems in the shift solenoid valves, valve body and automatic transmission.

HINT

Actual gear when a problem occurs in shift solenoid valve SL1

SHIFT SOLENOID VALVE REFERENCE

TCM commanded gear 1st 2nd 3rd 4th 5th 6th 7th 8th
Actual gear during SL1 stuck ON malfunction 1st 2nd 3rd 4th 5th 6th 7th 8th
Actual gear during SL1 stuck OFF malfunction N(1) N(1) N(1) N(1) N(1) 6th 7th 8th
(1) Neutral
DTC DETECTION CONDITION AND TROUBLE AREA

DTC Code DTC Detection Condition
  1. Diagnosis Condition
  2. Malfunction Status
  3. Malfunction Time
  4. Other
 Trouble Area
P0746
  1. ECT is 40°C (104°F) or more, ATF temperature is -10°C (14°F) or more, and vehicle is driven with shift lever in D (no malfunctions are detected in shift solenoid valve SL1, 2, 3, 4 and 5, SR, speed sensors (NT, NC3, SP2), oil pressure switch, water temperature sensor, oil temperature sensor, knock control sensor, electronic throttle, or CAN2)
  2. When gear shift to 6th, 7th, and 8th is requested by TCM, oil pressure switch is ON
  3. Malfunction status is detected 2 times per trip
  4. 2 trip detection logic
  • Shift solenoid valve SL1
  • Oil pressure switch
  • Valve body assembly
  • Automatic transmission assembly
P0746
  1. ECT is 40°C (104°F) or more, ATF temperature is -10°C (14°F) or more, and vehicle is driven with shift lever in D (no malfunctions are detected in shift solenoid valve SL1, 2, 3, 4 and 5, SR, speed sensors (NT, NC3, SP2), oil pressure switch, water temperature sensor, oil temperature sensor, knock control sensor, electronic throttle, or CAN2)
  2. When gear shifts to 1st to 5th are requested by TCM, engine speed overruns (neutral status)
  3. Malfunction status continues for 0 5 sec or more
  4. 2 trip detection logic
  • Shift solenoid valve SL1
  • Shift solenoid valve SLT
  • Valve body assembly
  • Automatic transmission assembly
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