Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptor
DTC P0116: Engine Coolant Temperature (ECT) Sensor PerformanceDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
ECT Sensor Signal | P0117 | P0118 | P0118 | P0116, P0128 |
Low Reference | -- | P0118 | P0118 | P0128 |
Typical Scan Tool Data
Circuit | Normal Range | Short to Ground | Open | Short to Voltage |
|---|---|---|---|---|
Operating Conditions: Key ON, engine OFF | ||||
ECT Sensor Signal | Varies¹ | 150°C (302°F) | -40°C (-40°F) | -40°C (-40°F) |
Low Reference | -- | -- | -40°C (-40°F) | -40°C (-40°F) |
¹ Varies -39 to +149°C (-38 to +300°F) | ||||
Circuit/System 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 low reference circuit. When the engine coolant temperatures are low, the resistance is high. When the engine coolant temperatures are high, the resistance is low. The ECM uses this high side coolant rationality test to determine if the ECT input is skewed. The ECM will record the amount of time the engine is OFF. At restart, the ECM will compare the temperature difference between the ECT and the intake air temperature (IAT) sensor 2.
Conditions for Running the DTC
| • | DTCs P0117, P0118, P0182, P0183 are not set. |
| • | The engine OFF timer is greater than 10 hours. |
| • | The ignition is ON. |
| • | The engine run time is greater than 2 seconds. |
| • | The start-up IAT is greater than 10°C (50°F). |
| • | DTC P0116 runs once per drive cycle within the enabling conditions. |
Conditions for Setting the DTC
| • | The ECM detects a start-up temperature difference between the ECT sensor and the IAT sensor 2 of more than 5.3°C (9.5°F), the vehicle must be driven for more than 360 seconds over 24 km/h (15 mph). If the IAT sensor 2 temperature decreases more than 5.3°C (41.5°F), a block heater is detected and the test is aborted. If the IAT sensor 2 temperature does not decrease, a block heater was not detected and DTC P0116 sets. |
| • | The ECM detects a start-up temperature difference between the ECT sensor and the IAT sensor 2 of more than 100°C (212°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 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
| • | A snapshot is the quickest method to capture the ECT and the IAT sensor 2 data before it changes. |
| • | An IAT sensor 2 that is skewed low can cause this DTC to set. |
| • | A high resistance short from the signal circuit to the low reference circuit can cause this DTC to set. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
Important: The engine needs to have been OFF for at least 10 hours for the ECT and the IAT sensor 1 to be at ambient temperature. The vehicle should not have changed environments during this time.
- If the ignition has been OFF for 10 hours or more, the ECT and the IAT sensor 2 should be within 6°C (11°F) of each other, and also the ambient temperature. Turn ON the ignition, with the engine OFF, and use a scan tool to observe the IAT sensor 2 and the ECT sensor parameters. Compare those sensor parameters to each other, and also to the ambient temperature. A slight to moderate resistance in the IAT signal or low reference circuit can widen the spread between the two sensors and cause this DTC to set.
- An IAT sensor 2 that is skewed lower at various ambient temperatures, due to more resistance than is normal, can widen the spread between the two sensors and cause this DTC to set. Measure and record the resistance of the IAT sensor 2 at various ambient temperatures, then compare those measurements to the Temperature vs. Resistance table. Refer to Temperature Versus Resistance .
- Inspect the ECT sensor terminals for corrosion and for engine coolant leaking through the sensor.
- Inspect the cooling system surge tank for the proper engine coolant level. Refer to Cooling System Leak Testing and Cooling System Draining and Filling .
- Engine running, observe the DTC information with a scan tool. DTC P0116 should not set.
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Caution: Under pressure, the temperature of the solution in the radiator can be considerably higher, without boiling. Removing the radiator cap while the engine is hot (pressure is high), will cause the solution to boil instantaneously, with explosive force. The solution will spew out over the engine, fenders, and the person removing the cap. Serious bodily injury may result. Flammable antifreeze, such as alcohol, is not recommended for use at any time. Flammable antifreeze could cause a serious fire.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the ECT sensor.
- Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit terminal A and ground.
- Ignition ON, verify the scan tool ECT parameter is less than -39°C (-40°F).
- Install a 3A fused jumper wire between the signal circuit terminal B and the low reference circuit terminal A. Verify the scan tool ECT parameter is greater than 149°C (300°F)
- If all circuits test normal, test or replace the ECT sensor.
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the control module. |
| ⇒ | If greater than the specified range, test the signal circuit terminal B for a short to ground. If the circuit tests normal, replace the control module. |
| ⇒ | If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the control module. |
Component Testing
Measure and record the resistance of the ECT sensor at various ambient temperatures and compare those measurements to the Temperature vs. Resistance table. Refer to Temperature Versus Resistance .
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for engine control module (ECM) replacement, setup, and programming |
