Toyota Electronically Controlled Transmission Service Manual

Quick guide from the manual

This document provides essential wiring diagrams, system operation outlines, and diagnostic service hints for the Toyota Electronically Controlled Transmission. It is intended for technicians to troubleshoot electrical issues, verify sensor signals, and locate connectors within the vehicle harness.

• System Operation: Understand how the Engine Control Module (ECM) manages gear shifts, lock-up, and overdrive.
• Diagnostics: Use the provided voltage and resistance values to test solenoids, switches, and sensors.
• Wiring Diagrams: Refer to the schematics for signal paths between the ECM and transmission components.

System Outline

The electronically controlled transmission uses the engine control module to manage gear shifts based on input signals from various sensors. Key functions include:

• Gear Shift Operation: The ECM selects the appropriate gear based on engine coolant temperature and vehicle speed signals. Current is output to solenoids to engage specific gears.
• Lock-up Operation: When conditions are met, the ECM activates the lock-up solenoid to improve efficiency.
• Stop Light Switch Circuit: Depressing the brake pedal sends a signal to the ECM to cut continuity to the lock-up solenoid.
• Overdrive Circuit: The O/D main switch allows the driver to enable or disable overdrive. The ECM monitors this switch to control shifting.
• A/T Oil Temp Warning: If fluid temperature exceeds 150°C (302°F), the ECM activates a warning light. The light turns off once the temperature drops to 120°C (248°F) or less.

Service Hints and Diagnostics

Use these values to verify component health using a multimeter:

• Transmission Solenoid: Resistance should be approximately 13 Ohm.
• Park/Neutral Position Switch: Should show approximately 12 volts with the ignition switch in the ACC position.
• Engine Control Module (ECM) Terminals:
  • S1-E1: 9-14 volts.
  • S2, SL-E1: 0-1.5 volts.
  • THW-E2: 0.2-1.0 volts (at 80°C coolant temp).
  • VTA-E2: 0.3-0.8 volts (throttle fully closed) to 3.2-4.9 volts (throttle fully open).
  • +B/BATT-E1: 9-14 volts.

Parts and Connector Locations

The manual includes detailed tables for locating parts, relay blocks, and ground points. Refer to the specific pages listed in the parts location table to find the physical location of connectors (e.g., J12, E4) and ground points (e.g., EA, EB) within the vehicle.