P0116

DTC P0116

CIRCUIT DESCRIPTION
The engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The engine control module (ECM) supplies 5 volts to the signal circuit and a ground for the ECT low reference circuit. When the ECT is low, the sensor resistance is high. When the ECT is high, the sensor resistance is low. The ECM uses this input for engine controls and enabling criteria for diagnostics. The ECM uses this High Side Coolant Rationality test to determine if the ECT input is skewed high. The internal clock of the ECM will record the amount of time the ignition is OFF. At restart the ECM will compare the temperature difference between the ECT and the intake air temperature (IAT). This DTC will only run once during the ignition cycle within the enabling conditions. Before failing this test, the ECM will perform a calculation to determine the presence of a block heater. If the ECM detects that the temperature difference is not within the calibrated range after the ignition OFF time, DTC P0116 sets.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P0116 Engine Coolant Temperature (ECT) Sensor Performance

CONDITIONS FOR RUNNING THE DTC
- The ignition OFF time is more than 10 hours.
- The IAT sensor temperature is more than 7°C (44°F) at key up.
- A diagnostic test will need to be performed to determine if the temperature difference is caused by a block heater after the above conditions are met. The following item is the criterion to enable this test.
- The vehicle speed must be more than 24 km/h (15 mph) for more than 400 seconds.
- If the difference between the IAT and the ECT is more than 15°C (27°F) at start-up, the vehicle speed must be more than 24 km/h (15 mph) for more than 400 seconds.

CONDITIONS FOR SETTING THE DTC
- If the IAT decreases more than 3°C (5°F) during the test, a block heater was detected, this diagnostic will abort and no DTC will set.
- If the IAT does not decrease during the test, DTC P0116 will set.

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.

TEST DESCRIPTION

Step 1 - Step 8:

Step 9 - Step 14:

Step 15 - Step 27:

The numbers below refer to the step numbers on the diagnostic table.
7. A snapshot is the quickest method to capture the data before it changes.
8. An IAT sensor that is skewed low can cause this DTC to set.
10. This step will determine if high resistance has caused this DTC to set.
12. A high resistance short from the signal circuit to the low reference circuit can cause this DTC to set.