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Home >> Lexus >> 2002 >> SC 430 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P1121: Accelerator Pedal Position Sensor Circuit Malfunction >> Diagnosis & Repair

Diagnosis & Repair

  1. Disconnect accelerator pedal position sensor connector. Using an ohmmeter, measure resistance between each terminal at 68°F (20°C). See ACCELERATOR PEDAL POSITION SENSOR RESISTANCE  table. See Figure. If resistance is to specification, go to next step. If resistance is not to specification, go to step  3.
    ACCELERATOR PEDAL POSITION SENSOR RESISTANCE

    Terminals Resistance
    Vcp1-Ep1 1.5-6.0 K/Ohms
    Vcp2-Ep2 1.5-6.0 K/Ohms
  2. Backprobing ECM connector E5, measure voltage between terminals No. 33 (Red/Yellow wire) and No. 26 (Green wire) at ECM E5 connector. See Figure. With fully closed throttle, voltage should be .5-1.1 volt. With Wide Open Throttle (WOT), voltage should be 3.0-4.6 volts. Measure voltage between terminals No. 32 (Black/White wire) and No. 34 (Brown wire) at ECM E5 connector. With fully closed throttle, voltage should be .9-2.3 volts. With WOT, voltage should be 3.4-5.0 volts. If voltage is not as specified, go to next step. If voltage is as specified, replace ECM and retest.
  3. Disconnect ECM E5 connector. Ensure continuity is present in Green and Brown wires between accelerator position sensor and ECM. See Figure. Ensure no continuity is present in Green and Brown wires between accelerator position sensor and ground. Repair wiring as necessary. See WIRING DIAGRAMS article. If wiring is okay, replace accelerator pedal.
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