Circuit Description
The engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. When the engine coolant temperatures are low, the resistance of the sensor is high. When the engine coolant temperatures are high, the resistance of the sensor is low. The ECT sensor has a signal circuit and a low reference circuit. The engine control module (ECM) supplies 5 volts to the ECT signal circuit and supplies a ground tot he ECT low reference circuit. The ECM uses the following sensor inputs to calculate a predicted engine coolant temperature:
| • | The ECT sensor |
| • | The intake air temperature (IAT) |
| • | The mass air flow (MAF) sensor |
| • | The engine speed (RPM) |
The ECM compares the actual engine coolant temperature to a predicted engine coolant temperature. If the ECM detects that the actual engine coolant temperature is more than the predicted engine coolant temperature, DTC P0116 sets.
Conditions for Running the DTC
| • | DTCs P0112, P0113, P0117, P0118, P0125, P0128, P0601, P0602, P0603, P0604, P0606 are not set. |
| • | The engine run time is more than 8 minutes. |
| • | The engine speed is more than 400 RPM. |
| • | The accumulated MAF value is equal to a calculated value. |
Conditions for Setting the DTC
The ECM detects a temperature difference of more than 20°C (36°F) between the actual engine coolant temperature and the predicted engine coolant temperature.
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 inspecting the ECT sensor, the Temperature vs Resistance table should be used in order to determine if a skewed sensor is the concern. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for excessive resistance in the ECT sensor circuit.
-
This step tests for excessive resistance in the IAT sensor circuit.
-
This step tests for a skewed sensor through the range of temperatures affecting this DTC.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
2 | Is the cooling system low on coolant? | -- | Go to Loss of Coolant in Engine Cooling | Go to Step 3 |
Does the scan tool indicate that the ECT temperature is more than the specified value? | 139°C (282°F) | Go to Step 4 | Go to Step 5 | |
Does the scan tool indicate that the IAT sensor temperature is more than the specified value? | 139°C (282°F) | Go to Step 8 | Go to Diagnostic Aids | |
5 |
Does the scan tool indicate that the ECT sensor temperature is more than the specified value? | 139°C (282°F) | Go to Step 6 | Go to Step 7 |
6 | Test the low reference circuit for high resistance, or an open. Refer to Circuit Testing in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Diagnostic Aids |
7 | Test the signal circuit for high resistance, or an open. Refer to Circuit Testing in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Diagnostic Aids |
Does the resistance and temperature closely match the Temperature vs Resistance table? | 10-90°C (50-194°F) | Go to Step 9 | Go to Step 10 | |
9 | Install the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Is the action complete? | -- | Go to Diagnostic Aids | -- |
10 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Did you complete the action? | -- | Go to Step 11 | -- |
11 |
Does the DTC run and pass? | -- | Go to Step 12 | Go to Step 2 |
12 | Observe the stored information, Capture Info, with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
