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Check And Replace Ecu

NOTE:

The connector should not be disconnected from the ECU. Perform the inspection from the backside of the connector on the wire harness side.
When no measuring condition is specified, perform the inspection with the engine stopped and the ignition switch ON.
Check that the connectors are fully seated. Check for loose, corroded or broken wires.

First check the ECU ground circuit. If it is faulty, repair. If it is normal, the ECU could be faulty. Replace the ECU with a normal functioning one and check if the symptoms occur. If the trouble symptoms stop, replace the ECU.
1. Measure the resistance between the ECU ground terminal and body ground.
  Resistance: Below 1 Ω
  
  Fig 1: Checking Resistance Between ECU Ground Terminal And Body Ground
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Disconnect the ECU connector. Check the ground terminals (on the ECU side and wire harness side) for evidence of bending, corrosion or foreign material. Lastly check the contact pressure of the female terminals.
  
  Fig 2: Identifying Ground Terminals
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002