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 coolant temperatures are low, the resistance is high. When the coolant temperatures are high, the resistance is low. The ECM uses this input for engine controls and enabling criteria for diagnostics. 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 intake air temperature (IAT). If the temperature difference is not within the calculated amount after the ignition OFF time, DTC P0116 sets. Before failing this test, the ECM will perform a calculation to determine the presence of a block heater.
Conditions for Running the DTC
| • | DTCs P0112, P0113, P0117, P0118, P0125, P0128, P0500, P0603 are not set. |
| • | The engine is running. |
| • | The vehicle has a minimum ignition OFF time of 7.5 hours. |
| • | The vehicle speed is more than 16 km/h (10 mph) for more than 10 seconds. |
| • | This diagnostic has not previously run this ignition cycle. |
Conditions for Setting the DTC
The difference between start-up ECT and IAT is more than 15°C (27°F).
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 testing the ECT sensor or the IAT sensor, the Temperature vs Resistance table should be used to determine if a skewed sensor is the problem. |
| • | If the vehicle has been allowed to sit overnight, the ECT and IAT should be near the ambient temperature. |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Engine Control Module Connector End Views | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
2 | Is the cooling system coolant low? | -- | Go to Loss of Coolant in Engine Cooling | Go to Step 3 |
3 |
Is the ECT sensor parameter more than the specified value? | 149°C (300°F) | Go to Step 4 | Go to Step 5 |
4 |
Is the IAT sensor parameter more than the specified value? | 149°C (300°F) | Go to Step 8 | |
5 | Connect a 3-amp fused jumper wire between the signal circuit of the ECT sensor and a good ground. Is the ECT sensor parameter more than the specified value? | 149°C (300°F) | Go to Step 6 | Go to Step 7 |
6 | Test the ECT sensor low reference circuit for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 9 |
7 | Test the ECT sensor signal circuit for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 9 |
8 | Test for an intermittent and for a poor connection at the ECT sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 |
9 | Test for an intermittent and for a poor connection at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Diagnostic Aids |
10 |
Does the resistance and temperature closely match the Temperature vs Resistance table? | 10-90°C (50-194°F) | Go to Step 11 | Go to Step 12 |
11 | Install the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Is the action complete? | -- | Go to Diagnostic aids | -- |
12 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- |
13 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 14 |
14 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
