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Home >> Lexus >> 1990 >> LS 400 >> Repair and Diagnosis >> Brakes >> Traction Control >> Traction Control System >> Diagnostic Charts >> Code 45 & 46: Main Throttle Position Sensor Circuit >> Diagnostic Chart
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Diagnostic Chart

  1. Check the diagnostic code for the engine. Repair and clear codes. If there are no codes, go to next step.
  2. Check voltage between terminal VTH of ABS & TRAC ECU connector and body ground. Remove ABS & TRAC ECU with connector still connected. Remove intake air duct. Turn ignition switch on. Check voltage between terminal VTH of ABS & TRAC ECU connector and body ground. When the main throttle valve is turned from fully closed position to fully opened position by hand. With throttle fully closed, voltage should be appx. 0.6V. With throttle fully opened, voltage should be appx. 3.8V. As the main throttle valve is turned, the voltage should increase gradually without interruption. If voltage is okay, go to step 4). If voltage is not okay, go to next step.
  3. Check harness and connector between ABS & TRAC ECU and engine & ECT ECU. Repair or replace any faulty connectors or harnesses. If connectors are okay, check and replace ABS & TRAC ECU.
  4. Check voltage between terminal IDL1 of ABS & TRAC ECU connector and body ground. Turn ignition switch on. Measure voltage between terminal IDL of ABS & TRAC ECU connector and body ground when the main throttle valve is fully closed and fully opened. When main throttle valve is fully closed, voltage should be 0V. When main throttle valve is fully opened, voltage should be apx. 5V. If voltage is okay, check and replace ABS & TRAC ECU. If voltage is not okay, go to next step.
  5. Check harness and connector between ABS & TRAC ECU and main throttle position sensor. Repair or replace any faulty connectors or harnesses. If connectors are okay, check and replace ABS & TRAC ECU.
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