DTC P0126
DTC P0128 Coolant thermostat stuck to open
DETECTION
CONDITION
DTC P0126
If ECT signal never exceeds 71C {160F} after engine start for specified period, PCM determines that the
coolant thermostat is stuck open.
MONITORING CONDITIONS
IAT:
Above -10C {14F}
Difference between ECT at engine start and minimum IAT:
Below 6C {43F}
Vehicle speed
over 9.5 km/h {5.9 mph}
DTC P0128
PCM monitors MAF, IAT, VSS and ECT 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
ECT at engine start:
Below 35C {95F}
IAT:
Above -10C {14F}
Difference between ECT at engine start and minimum IAT:
Below 6C {43F}
Vehicle speed
above 25 km/h {15 mph} for ATX, 40 km/h {25 mph} for MTX
Diagnostic support note
This is a intermittent monitor (THERMOSTAT)
MIL illuminates if PCM detects the above malfunction condition in two consecutive drive cycles.
DIAGNOSTIC MONITORING TEST RESULTS is available.
PENDING CODE is available if PCM detects the above malfunction condition during first drive cycle.
FREEZE FRAME DATA is available.
DTC is stored in PCM memory.
POSSIBLE
CAUSE
Coolant thermostat malfunction
ECT sensor malfunction
PCM malfunction