Details On DTCs

WARNING: This page is about a different car, the 2020 Mazda CX-30. However, it is still accessible from the selected car via links, so may be relevant.

DTC P0126:00 (PCM, SKYACTIV-G) DETECTION CONDITION AND POSSIBLE CAUSE

Description	Thermostat stuck open
Detection condition	Determination conditions	If any of the following conditions is met under condition A or condition B: Condition A: ECT sensor No. 1 detected temperature is less than 76.9°C {170°F} Condition B: ECT sensor No. 1 detected temperature is less than 60°C {140°F}
	Preconditions	Condition A: If the following condition is implemented 3 times or more. Vehicle is driven for approx. 35.9 s at a speed of 40 km/h {25 mph}, and engine coolant heat radiation amount ^1 is frequently at specified value W/K or more compared to specified value W/K or less. The actual engine coolant temperature is 18.9°C {34°F} higher than the estimated ambient temperature calculated by the PCM based on the values input. Engine coolant temperature at engine start: within specified value ^2 Estimated ambient air temperature: -10-45°C {14-113°F} Within 25 min after engine start The following DTCs are not detected: MAF sensor malfunction: P0100:00 and U060F:00 ECT sensor No. 1 malfunction: P0117:00 and P0118:00 Fuel system malfunction: P0171:00, P0172:00, P2096:00 and P2097:00 Condition B: If the following condition is implemented 3 times or more. Vehicle is driven for approx. 35.9 s at a speed of 40 km/h {25 mph}, and engine coolant heat radiation amount ^1 is frequently at specified value W/K or more compared to specified value W/K or less. The actual engine coolant temperature is 18.9°C {34°F} higher than the estimated ambient temperature calculated by the PCM based on the values input. Estimated ambient air temperature: more than -10°C {14°F} The following conditions continue for 2 s or more. ECT sensor No. 1 detected temperature: more than 76.9°C {170°F} ECT sensor No. 1 detected temperature: 73.9°C {165°F} or less The following DTCs are not detected: MAF sensor malfunction: P0100:00 and U060F:00 ECT sensor No. 1 malfunction: P0117:00 and P0118:00 Fuel system malfunction: P0171:00, P0172:00, P2096:00 and P2097:00 ^1 : The engine coolant heat radiation amount is the value calculated by the PCM. ^*2 : Standard can be verified by displaying PIDs using M-MDS
	Drive cycle	2
	Self test type	CM DTC self test
	Sensor used	Desired engine coolant temperature: intake air temperature (IAT sensor), engine speed (CKP sensor), charging efficiency Actual engine coolant temperature: ECT sensor No. 1
Fail-safe function	Not applicable
Vehicle status when DTCs are output	Heating is ineffective after engine is started
Possible cause	ECT sensor No. 1 malfunction Poor assembly of ECT sensor No. 1 Poor assembly of engine coolant hose (engine coolant passage malfunction) Poor engine coolant, leakage, or freezing Use of unspecified engine coolant Foreign matter caught in thermostat (foreign matter penetration in engine coolant) Thermostat (built-into coolant control valve) malfunction PCM malfunction