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Home >> Toyota >> 2001 >> Sienna CE >> Repair and Diagnosis >> External Pages >> Different car >> Section 115 (Engine Control System Self Diagnostics - 4-Cylinder) >> Diagnostic Tests >> DTC P0128: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) >> Diagnosis & Repair

Diagnosis & Repair

WARNING: This page is about a different car, the 2003 Toyota Camry Solara. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Read freeze frame data using the hand-held tester or OBD II scan tool, as freeze frame data records the engine conditions when a malfunction is detected. When trouble shooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.
  1. Check the thermostat. See appropriate article in ENGINES. If the results are okay, go to next step. If the results are not good, replace the thermostat. See appropriate article in ENGINES.
  2. Check if there are any other codes (besides DTC P0128) being output. If there are other codes output, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If there are not other codes output, check and replace the ECM. To check ECM inputs and outputs, see PIN VOLTAGE CHARTS article. For ECM location, see ENGINE CONTROL MODULE LOCATION  under SELF-DIAGNOSTIC SYSTEM.
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