OBD II scan tool (excluding hand-held tester):

WARNING: This page is about a different car, the 2004 Lexus ES 330. However, it is still accessible from the selected car via links, so may be relevant.

INSPECT ACCELERATOR PEDAL ASSY (ACCELERATOR PEDAL POSITION SENSOR)
1. Disconnect the A25 accelerator pedal position sensor connector.
2. Measure the resistance between each terminal.
  Standard:
  
  Fig 1: Accelerator Pedal Position Sensor Connector Terminals Condition Chart
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
3. Reconnect the accelerator pedal position sensor connector.
  
  Fig 2: Identifying Accelerator Pedal Position Sensor Connector
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
NG: REPLACE ACCELERATOR PEDAL ASSY (See ACCELERATOR PEDAL ASSY (3MZ-FE (NORMAL PEDAL) )

OK: GO TO NEXT STEP.
INSPECT ECM (VPA AND VPA2 VOLTAGE)
1. Turn the ignition switch ON.
2. Measure the voltage between the specified terminals of the E6 ECM connector.
  Standard:
  
  Fig 3: ECM Terminals Specified Condition Chart
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  
  Fig 4: Identifying ECM Connector Terminals
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
OK: Go to step 4

NG: GO TO NEXT STEP.
CHECK HARNESS AND CONNECTOR (ACCELERATOR PEDAL POSITION SENSOR - ECM)
1. Disconnect the A25 accelerator pedal position sensor connector.
2. Disconnect E6 the ECM connector.
3. Check the resistance between the wire harness side connectors.
  Standard: (Check for open)
  
  Fig 5: Accelerator Pedal Position Sensor And ECM Terminals Specified Condition Chart (Check For Open)
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  
  (Check for short)
  
  Fig 6: Accelerator Pedal Position Sensor And ECM Terminals Specified Condition Chart (Check For Short)
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
4. Reconnect the accelerator pedal position sensor connector.
5. Reconnect the ECM connector.
  
  Fig 7: Identifying Accelerator Pedal Position Sensor Connector
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  
  Fig 8: Disconnecting E6 ECM Connector
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
NG: REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: GO TO NEXT STEP.
REPLACE ACCELERATOR PEDAL ASSY (See ACCELERATOR PEDAL ASSY (3MZ-FE (NORMAL PEDAL) )
GO: GO TO NEXT STEP.
READ OUTPUT DTC (SEE IF ACCELERATOR PEDAL POSITION SENSOR DTCS ARE OUTPUT AGAIN)
1. Clear the DTC (see DTC CHECK/CLEAR ).
2. Start the engine.
3. Run the engine at idle for 15 seconds or more.
4. Read the DTC (see DTC CHECK/CLEAR ).
  Result:
  
  Fig 9: DTC Output Result Table
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
B: SYSTEM OK

A: GO TO NEXT STEP.

REPLACE ACCELERATOR PEDAL ASSY (See ECM (3MZ-FE) )