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Home >> Infiniti >> 2003 >> Q45 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0128: Thermostat Function >> DTC Confirmation Test
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DTC Confirmation Test

  1. Replace thermostat with new one. Use only a genuine NISSAN thermostat as a replacement. If an incorrect thermostat is used, the MIL may come on.
  2. Turn ignition on. Select COOLAN TEMP/S in DATA MONITOR mode with scan tool. Check that the COOLAN TEMP/S is above 140°F (60°C). If it is below 140°F (60°C), go to next step. If it is above 140°F (60°C), stop engine and cool down the engine to less than 140°F (60°C), then retest.
  3. Drive vehicle for 10 consecutive minutes at speeds of 50-75 MPH. If 1st trip DTC is detected, go to DIAGNOSTIC PROCEDURE  . If 1st trip DTC is not detected, system is okay at this time.
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