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Diagnosis & Repair

WARNING: This page is about a different car, the 2002 Toyota Sienna. However, it is still accessible from the selected car via links, so may be relevant.
  1. Remove and inspect cooling system thermostat for damage and proper operation. Thermostat is located behind thermostat housing at flywheel end of engine, near end of intake manifold. If thermostat is okay, go to next step. If thermostat is defective, replace thermostat.
  2. Using Toyota hand-held tester or scan tool, check for any other DTCs. If other DTCs exist, diagnose and repair those DTCs first and retest. If only DTC P0128 exists, replace ECM. ECM is located at passenger's side of instrument panel, just below glove box. See Figure.
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