P0116

CIRCUIT DESCRIPTION
An engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The powertrain control module (PCM) supplies 5 volts to the signal circuit. When coolant temperatures are low, resistance is high. When coolant temperatures are high, the resistance is low. The PCM uses this input for engine controls and enabling criteria for diagnostics. The PCM will record the amount of time the engine is OFF. At restart, the PCM will compare the temperature difference between the ECT and intake air temperature (IAT). If the temperature difference is not within the calculated amount after the predetermined soak time, this DTC will set. Before failing this test, the PCM will check for the presence of a block heater.

CONDITIONS FOR RUNNING THE DTC
^ The ignition is ON.
^ DTCs P0112, P0113, P0117, P0118, P0125, P0128, P0601, P0602, P0604, P0606, P1621, or P1683 are not set.
^ The vehicle has a minimum soak time of 8 hours.
^ The IAT is greater than 15°C (59°F).
^ The engine has a minimum soak time of 28,800 seconds (8 hours).

CONDITIONS FOR SETTING THE DTC
The difference between the ECT and IAT temperature is greater than 15°C (59°F).

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles.
^ The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool Freeze Frame/Failure Records.

CONDITIONS FOR CLEARING THE MIL OR DTC
^ The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed.
^ A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle.
^ Use a scan tool in order to clear the DTCs.

DIAGNOSTIC AIDS
^ DTC P0116 is designed to detect an ECT sensor that is skewed high.
^ An IAT sensor that is skewed could cause this DTC to set.
^ When checking the ECT sensor, the Temperature vs Resistance table should be used in order to determine if a skewed sensor is the problem.
^ If the engine has been allowed to sit overnight, the ECT and EAT temperature should be within the calculated amount.

TEST DESCRIPTION

Steps 1-7:

Steps 8-12:

The numbers below refer to the step numbers on the diagnostic table:
3. This step tests for excessive resistance in the ECT circuit.
4. This step tests for excessive resistance in the ECT sensor circuit.
5. This step tests for a skewed sensor through the range of temperatures affecting this DTC.