P0125

Schematic:

Temperature Vs Resistance:

The Engine Coolant Temperature (ECT) sensor is a thermistor type sensor. When coolant temperature is cold the sensor has a high resistance; as temperature increases the resistance of the sensor decreases. The PCM provides a 5 volt signal to the coolant sensor, which is also connected to PCM ground. The PCM reads the voltage drop on the signal line to determine coolant temperature. DTC P0125 will set if ECT sensor does not reach 40°C (113°F) after a calculated (based on start-up coolant temp) total air flow has been reached.

DTC PARAMETERS
DTC P0125 will set if ECT sensor does not reach 40°C (113°F) after a calculated (based on start-up coolant temp) total air flow has been reached and the following conditions are met:
^ Start-up ECT was between -40°C (-40°F) and 35°C (95°F).
^ IAT is greater than -7°C (19°F).
^ Calculated average air flow is greater than 10 g/sec.
^ Engine run time is between 30 and 1200 seconds.
^ Distance traveled is greater than 0.5 miles (0.8 km).

IMPORTANT: Distance is only updated when vehicle speed is greater than 25 mph and calculated air flow is greater than 10 g/sec.)

^ DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0130, P0171, P0172, P0201, P0202, P0203, P0204, P0300, P0336, P0440, P0442, P0446, P0480, P0481, P0502, P0503, P0602, P1441 and P1621 are not set.

DIAGNOSTIC AIDS
DTC P0125 indicates lower than normal coolant temperatures and probably does not indicate a faulty ECT subsystem.

Possible causes of low coolant temperature:
^ Thermostat stuck open.
^ Cooling fans always On.
^ Skewed ECT sensor or resistance in wiring. (Refer to "Temperature vs. Resistance" chart.)