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Home >> Lexus >> 1991 >> LS 400 >> Repair and Diagnosis >> Brakes >> Traction Control >> Traction Control System >> Diagnostic Charts >> Code 47 & 48: Sub-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 VSH of ABS & TRAC ECU connector and body ground. Remove ABS & TRAC ECU with connectors still connected. Remove intake air duct. Disconnect step motor connector. Turn ignition switch on. Check voltage between terminal VSH of ABS & TRAC ECU connector and body ground, when the sub-throttle valve is turned from fully opened position to fully closed position. When the sub-throttle valve is fully closed, voltage should be appx. 0.6V. When the sub-throttle valve is fully opened, voltage should be appx. 3.7V. In addition, as the sub-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 IDL2 of ABS & TRAC ECU connector and body ground. Turn ignition switch on. Measure voltage between terminal IDL2 of ABS & TRAC ECU connector and body ground, when the sub-throttle valve is fully closed and fully opened. When the sub-throttle valve is fully closed, voltage should be 0V. When the sub-throttle valve is fully opened, voltage should be appx. 5V. If voltage is okay, check and replace ABS & TRAC ECU.
  5. Check harness and connector between ABS & TRAC ECU and sub-throttle sensor. Repair or replace any faulty connectors or harnesses. If connectors are okay, check and replace ABS & TRAC ECU.
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