P0116

CIRCUIT DESCRIPTION
The 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 the enabling criteria for the diagnostics. The PCM will record the amount of time that the engine is OFF. At restart, the PCM will compare the temperature difference between the ECT and the intake air temperature (IAT). If the temperature difference is not within the calculated amount after the predetermined soak time, this diagnostic trouble code (DTC) will set. Before tailing this test, the PCM will inspect 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, P1621, or P1683 are not set.
^ The vehicle has a minimum soak time of 8 hours.

CONDITIONS FOR SETTING THE DTC
^ The PCM may detect a temperature difference between the ECT and the IAT of more than 20°C (36°F). If this happens, the vehicle must be driven for 5 minutes over 24 km/h (15 mph). If the IAT decreases more than 7°C (12.6°F), a block heater is indicated and the test is aborted. If the IAT temperature does not decrease, a block heater was not detected and this DTC will set.
^ OR
At the start up, the temperature difference between the ECT and the IAT is more than 140°C (252°F).
^ AND
The cranking time for the engine without starting the engine is more than 10 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Clear the MIL and the DTC with a scan tool.

DIAGNOSTIC AIDS
^ DTC P0116 is designed to detect an ECT sensor that is skewed high.
^ An IAT sensor that is skewed low 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 the IAT 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 sensor circuit.
4. This step tests for excessive resistance in the IAT sensor circuit.
5. This step tests for a skewed sensor through the range of temperatures that is affecting this DTC.