P0126

DTC P0126 Engine Coolant Temperature (ECT) Insufficient For Stable Operation

Circuit Description

The engine coolant temperature (ECT) sensor is installed to the thermostat housing. The ECT sensor is a variable resistor and it measures the temperature of the engine coolant. If the coolant temperature does not increase normally or does not reach the regulating temperature of the thermostat the engine is considered not warm enough for stable low emission operation. Additionally other diagnostics that use engine coolant temperature as enabling criteria may not run when expected. If the ECM detects that the calibrated amount of fuel has been burnt and the ECT has not reached the minimum calibrated temperature this DTC will set. This DTC will only run once per driving cycle within the enabling conditions.

Condition for Running the DTC

^ DTCs P0016 P0112 P0113 P0116 P0117 P0118 P0201 - P0204 P0234 P0261 P0264 P0267 P0270 P0299 P0300 P0301 - P0304 P0335 P0336 P0500 P0602 P0642 P0643 P0652 P0653 P2146 - P2151 P129 and P268A are not set.
^ The ignition switch is ON.
^ The intake air temperature is more than 19°F (-7°C).
^ The startup engine coolant temperature is between -40 to 147°F (-40 to 64°C).
^ The engine runtime is longer than a calculated value depending on engine coolant temperature intake air temperature and fuel injection quantity.
^ The idling time rate (idling time! engine runtime) is smaller than 50%.

Condition for Setting the DTC

^ The maximum engine coolant temperature is less than 149°F (65°C) for longer than 2 seconds.

Action Taken When the DTC Sets

^ The ECM illuminates the MIL on the second consecutive driving cycle when the diagnostic runs and fails. Refer to DTC Type Definitions for Action Taken When the DTC Sets - Type B.

Condition for Clearing the DTC

^ Refer to DTC Type Definitions for Condition for Clearing the MIL/DTC - Type B.

Diagnostic Aids

^ This DTC is designed to detect a faulty thermostat(s).
^ After starting the engine the ECT should rise steadily to about 176 to 185°F (80 to 85°C) then stabilize when the thermostat opens.
^ Use the Temperature vs. Resistance table to test the ECT sensor at various temperature levels to evaluate the possibility of a skewed sensor. A skewed sensor could result in poor driveability concerns.

Circuit/System Testing DTC P0126