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, the 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). Before failing this test, the PCM will search for the presence of a block heater. If the temperature difference is not within the calculated amount, after the predetermined soak time, DTC P0116 sets.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | DTCs P0112, P0113, P0117, P0118, P0125, P0128, P0601, P0602, P1621, P1683 are not set. |
| • | The vehicle has a minimum soak time of 8 hours. |
Conditions for Setting the DTC
| • | The PCM detects a temperature difference between the ECT sensor and the IAT sensor of more than 100°C (180°F) at start up. |
| OR |
| • | The time spent cranking the engine without starting is more than 5 seconds, with a temperature difference between the ECT sensor and the IAT sensor more than 15°C (27°F). |
| OR |
| • | The PCM detects a temperature difference between the ECT sensor and the IAT sensor of more than 15°C (27°F), then the vehicle must be driven for 5 minutes over 24 km/h (15 mph). If the IAT sensor temperature decreases more than 7°C (12.6°F) then a block heater is detected and the test is aborted. If the IAT sensor temperature does not decrease, then a block heater was not detected and DTC P0116 sets. |
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. |
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: Powertrain 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 coolant low? | -- | Go to Loss of Coolant in Engine Cooling | Go to Step 3 |
Is the ECT sensor parameter more than the specified value? | 138°C (280°F) | Go to Step 4 | Go to Step 5 | |
Is the IAT sensor parameter more than the specified value? | 138°C (280°F) | Go to Step 8 | Go to Diagnostic Aids | |
Is the ECT sensor parameter more than the specified value? | 138°C (280°F) | Go to Step 6 | Go to Step 7 | |
6 | Test the low reference circuit for a high resistance or for 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 a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Diagnostic Aids |
8 |
Does the resistance and temperature closely match the Temperature vs Resistance table? | 10-90°C (50-104°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 | 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 12 | Go to Step 11 |
11 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 13 |
13 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
