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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 P0771: Shift Solenoid "E" Performance (Shift Solenoid Valve SR) >> 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 shift position when a problem occurs in shift solenoid valve SR.

SHIFT SOLENOID VALVE REFERENCE

TCM commanded gear 1st 2nd 3rd 4th 5th 6th 7th 8th
Actual gear during SR stuck OFF malfunction 1 7th 7th 7th 7th 7th 7th 7th 7th
Actual gear during SR stuck OFF malfunction 2 3rd 3rd 3rd 3rd 7th 7th 7th 7th
DTC DETECTION CONDITION AND TROUBLE AREA

DTC Code DTC Detection Condition
  1. Diagnosis Condition
  2. Malfunction Status
  3. Malfunction Time
  4. Other
 Trouble Area
P0771
  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), water temperature sensor, oil temperature sensor, knock control sensor, electronic throttle, or CAN2)
  2. When gear shifts to 4th to 5th are requested by TCM, engine speed overruns (neutral status)
  3. Malfunction status continues for 0 5 sec or more (1 trip)
  4. 2 trip detection logic
  • Shift solenoid valve SL2
  • Shift solenoid valve SR
  • Shift solenoid valve SLT
  • Valve body assembly
  • Automatic transmission assembly
P0771
  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), water temperature sensor, oil temperature sensor, knock control sensor, electronic throttle, or CAN2)
  2. One of following occurs
    1. When gear shifts to 1st are requested by TCM, actual gear changes to 3rd gear
    2. When gear shifts to 2nd are requested by TCM, actual gear changes to 3rd gear
    3. When gear shifts to 4th are requested by TCM, actual gear changes to 3rd gear
    4. When gear shifts to 5th are requested by TCM, actual gear changes to 7th gear
    5. When gear shifts to 6th are requested by TCM, actual gear changes to 7th gear
    6. When gear shifts to 8th are requested by TCM, actual gear changes to 7th gear
  3. Malfunction status occurs 2 times per trip
  4. 2 trip detection logic
  • Shift solenoid valve SL3
  • Shift solenoid valve SR
  • Valve body assembly
  • Automatic transmission assembly
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