Inspection Procedure

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.

CHECK HARNESS AND CONNECTOR (TRANSPONDER KEY ECU - ECM)
1. Disconnect the T20 ECU and E7 ECM connectors.
  
  Fig 1: Disconnecting T20 & E7 Connectors
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the resistance of the wire harness side connectors.
  Standard
  
  Fig 2: Measuring Resistance Between Transponder Key ECU & ECM Chart
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
NG: REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: Go to next step.
CHECK OPERATION OF TRANSPONDER KEY ECU
1. After replacing the transponder key amplifier, check that the engine starts.
  Standard:
  - Engine starts.
OK: REPLACE TRANSPONDER KEY ECU ASSY

NG: REPLACE ECM