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Electronic Controlled Automatic Transmission (ECT) - Diagnosis: Overview Lexus SC II

Automatic Trans 3 illustrations ~210 words

SYSTEM DESCRIPTION

The ECM uses the signals from the Throttle Position Sensor and Air-flow Meter to monitor the engagement condition of the lock up clutch.

Then the ECM compares the engagement condition of the lock up clutch with the lock up schedule in the ECM memory to detect mechanical trouble of the shift solenoid valve SLU, valve body, torque converter clutch and automatic transmission assembly (clutch, brake or gear etc.).

Scheme 89

Scheme 89: SYSTEM DESCRIPTION
DTC No.DTC Detecting ConditionTrouble Area
P2757Lock up does not occur when driving in the lock up range (normal driving at 80 km/h [50 mph]), or lock up remains ON in the lock up OFF range (2-trip detection logic).Shift solenoid valve SLU is stuck open or closed Valve body blocked up or stuck Lock up clutch Automatic transmission assembly

DTC P2757 DIAGNOSTIC

Scheme 90

Scheme 90: INSPECTION PROCEDURE

Scheme 91

Scheme 91
  1. INSPECT SHIFT SOLENOID VALVE (SLU) Remove the shift solenoid valve SLU. Connect the positive (+) lead from the battery to terminal 2 and the negative (-) lead to terminal 1. OK: NG: REPLACE SHIFT SOLENOID VALVE (SLU) OK: GO TO NEXT STEP
  2. INSPECT TRANSMISSION VALVE BODY ASSY (See chapter 2 in the problem symptoms table) NG: REPAIR OR REPLACE TRANSMISSION VALVE BODY ASSY OK: GO TO NEXT STEP
  3. INSPECT TORQUE CONVERTER CLUTCH ASSY (See «TORQUE CONVERTER CLUTCH AND DRIVE PLATE» ) NG: REPLACE TORQUE CONVERTER CLUTCH ASSY OK: REPAIR AUTOMATIC TRANSMISSION ASSY