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Home >> Mazda >> 2006 >> MX-5 Miata Base >> Repair and Diagnosis >> Engine Performance >> System >> On-Board Diagnostic [Engine Control System] >> DTC P0126, P0128 >> Notes
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DTC P0126, P0128: Notes

DETECTION CONDITION AND POSSIBLE CAUSE (DTC P0126, P0128)

DTC P0126
DTC P0128
Coolant thermostat stuck open
DETECTION CONDITION  DTC P0126 
  • If the ECT sensor signal never exceeds 71°C {160°F} after engine start for specified period, PCM determines that the coolant thermostat is stuck open.

MONITORING CONDITIONS 
  • IAT: above -10°C {14°F} 
  • Vehicle speed: over 6 km/h {3.7 mph} 

DTC P0128 
  • PCM monitors MAF, IAT, VSS and EAT signals and calculate radiator's heat radiation ratio while following monitoring conditions are met. If calculated value exceeds threshold, PCM determines that the coolant thermostat is stuck open.

    MONITORING CONDITIONS 

    • IAT: above -10°C {14°F} 
    • ECT at engine start: Below 36°C {97°F} 
    • Difference between ECT at engine start and minimum IAT: below 6°C {10.8°F} 
    • Vehicle speed: over 30 km/h {18.6 mph} 

Diagnostic support note 
  • This is an intermittent monitor (Engine cooling system).
  • The MIL illuminates if the PCM detects above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in PCM.
  • PENDING CODE is available if the PCM detects the above malfunction condition during the first drive cycle.
  • FREEZE FRAME DATA is available.
  • The DTC is stored in the PCM memory.
  • DIAGNOSTIC MONITORING TEST RESULT is available.
POSSIBLE CAUSE 
  • ECT sensor malfunction
  • Coolant thermostat malfunction
  • PCM malfunction