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Home >> Toyota >> 2001 >> Sienna CE >> Repair and Diagnosis >> External Pages >> Different car >> Section 24 (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 Tundra. 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 on driver's side front of engine, just behind cooling fan. 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 behind glove box and heater duct. See Figure.
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