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 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). If the temperature difference is not within the calculated amount after the predetermined soak time, this DTC will set.
The following table illustrates the difference between temperature, resistance, and voltage:
ECT | ECT Resistance | ECT Signal Voltage |
|---|---|---|
Cold | High | High |
Warm | Low | Low |
DTC Descriptors
This diagnostic procedure supports the following DTC.
DTC P0116 Engine Coolant Temperature (ECT) Sensor Performance
Conditions for Running the DTC
| • | The ignition is ON. |
| • | DTCs P0112, P0113, P0117, P0118, P0125, P0128, P0601, and P0602, are not set. |
| • | The vehicle has a minimum soak time of 8 hours. |
Conditions for Setting the DTC
If the PCM detects a temperature difference of more than 15°C (27°F) between the ECT and the IAT, the vehicle must be driven for 5 minutes over 24 km/h (15 mph) . If the IAT decreases more than 7°C (45°F) then 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.
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. Refer to DTC P0113 . |
| • | 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 IAT temperature should be within the calculated amount. |
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. Refer to DTC P0113 if the temperature does not indicate the specified value.
-
This step isolates the condition. If the temperature changes, test for a condition in the low reference circuit. If the temperature remains the same test the signal circuit for a condition.
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 low on coolant? | -- | Go to Loss of Coolant in Engine Cooling | Go to Step 3 |
3 | Is the customer's concern that the engine does not reach operating temperature or that the heater output is low? | -- | Go to Thermostat Diagnosis in Engine Cooling | Go to Step 4 |
4 |
Important: Return to this diagnostic procedure after you complete the thermostat diagnosis. Test for the correct operation of the thermostat. Refer to Thermostat Diagnosis in Engine Cooling. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 5 |
Is the temperature more than the specified value? | 138°C (280°F) | Go to Step 6 | Go to Step 7 | |
Is the temperature more than the specified value? | 138°C (280°F) | Go to Step 10 | Go to Diagnostic Aids | |
Is the temperature more than the specified value? | 138°C (280°F) | Go to Step 8 | Go to Step 9 | |
8 | Test the low reference of the ECT sensor 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 14 | Go to Step 11 |
9 | Test the signal circuit of the ECT sensor 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 14 | Go to Step 11 |
10 | Test for shorted terminals and for poor connections 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 14 | Go to Step 12 |
11 | Test for shorted terminals and for poor connections at the PCM. 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 14 | Go to Step 13 |
12 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
13 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
14 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 15 |
15 | Observe the stored information in Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
