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Home >> Toyota >> 2001 >> Sienna CE >> Repair and Diagnosis >> External Pages >> Different car >> Section 18 (Engine Control System Self-Diagnostics - V6) >> Diagnostic Tests >> DTC P0128: Thermostat Malfunction >> Diagnosis & Repair

Diagnosis & Repair

WARNING: This page is about a different car, the 2002 Toyota Highlander. However, it is still accessible from the selected car via links, so may be relevant.
  1. Remove and inspect cooling system thermostat. Thermostat is on flywheel side of engine, where lower radiator hose connects. If problem does not exist, go to next step. If problem exists, replace thermostat as necessary and retest.
  2. Using Toyota hand-held tester or scan tool, check for any other DTCs. If any other DTCs are displayed, diagnose and repair those DTCs first and retest. If only DTC P0128 is displayed, replace ECM.
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