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Home >> Toyota >> 2003 >> Matrix XRS, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self Diagnostics >> Diagnostic Tests >> DTC P0128: Thermostat Malfunction (Matrix Model) >> Diagnosis & Repair
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Diagnosis & Repair

NOTE:
  • If DTC P0115 or P0116 is output, first trouble shoot DTC P0115 or P0116. If no malfunction is detected, trouble shoot DTC P0128 next.
  • Read freeze frame data using TOYOTA hand-held tester or OBD II scan tool. Because freeze frame records engine conditions when malfunction is detected. When trouble shooting, it is useful for determining whether vehicle was running or stopped, engine was warmed up or not, air-fuel ratio was lean or rich, etc. at time of malfunction.
  1. Check cooling fan system. See appropriate article in ENGINE COOLING. If results are OK, go to next step. If results are not good, repair or replace cooling fan system.
  2. Check thermostat. See appropriate article in ENGINES. If results are OK, check and replace ECM. To check ECM inputs and outputs, see PIN VOLTAGE CHARTS article. To replace ECM, see REMOVAL & INSTALLATION - 4-CYLINDER article.
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