For 1990-2009 cars

### 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.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
ECT Sensor Signal | P0117, P0119 | P0118, P0119 | P0118¹ P0119¹ | P0116¹
Low Reference | -- | P0118, P0119 | P0118², P0119² | P0116²
¹ Sensor damage may occur if the circuit is shorted to B+. ² Internal ECM damage may occur if the circuit is shorted to B+.

### Typical Scan Tool Data

#### ECT Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Running Condition: The engine is running in Closed Loop. Parameter Normal Range: -39 to +142°C (-38 to +288°F), which varies with ambient temperature.
ECT Sensor Signal | 143°C (289°F) | -40°C (-40°F) | -40°C (-40°F)¹
Low Reference | -- | -40°C (-40°F) | -40°C (-40°F)¹
¹ Internal ECM or ECT sensor damage may occur if the circuit is shorted to B+.

### 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 ECT signal circuit and supplies a ground to the low reference circuit. The ECM monitors the mutual performance of the ECT and the intake air temperature (IAT) signals. The ECM monitors the warm up and cool down behavior of the sensors, after a vehicle driven at operating temperature is shut down. If the ECM detects that the ECT is not at the range of predetermined intake air temperature after cooling slowly for long time, or the ECT and the IAT are not in the specified range respectively compared with the last cold start, the DTC will set.

The following table illustrates the difference between temperature, resistance, and voltage:

Engine Coolant Temperature | Engine Coolant Temperature Resistance | ECT Signal Voltage
--- | --- | ---
Cold | Large | High
Warm | Small | Low

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0116 Engine Coolant Temperature (ECT) Sensor Performance

### Conditions for Running the DTC

#### Conditions 1

• | Before the ECM can report DTC P0116 failed, DTC P0101 must run and pass.

• | DTCs P0117, P0118, and P0119 are not set.

• | The engine run time of the previous ignition cycle was more than 10 minutes.

• | The accumulated air mass of the previous ignition cycle was more than 4,000 grams.

• | The minimum intake air temperature during the previous ignition cycle is between -30 to +2°C (-22 to +36°F).

• | Turn the ignition switch to ON position, the intake air temperature is between -30 to +2°C (-22 to +36°F).

• | DTC P0116 runs one time per ignition cycle once the above conditions are met.

#### Conditions 2

• | Before the ECM can report DTC P0116 failed, DTC P0101 must run and pass.

• | DTCs P0117, P0118, and P0119 are not set.

• | During the last turning OFF of the engine, the ECT is more than 85°C (185°F).

• | The ECM detects that the intake air temperature raise to the expected temperature when the ECM is OFF at the last ignition cycle. Open the hood or enhance the vent to prevent the intake air temperature raising.

• | The block heater is not detected.

• | DTC P0116 runs one time per ignition cycle once the above conditions are met.

#### Conditions 3

• | The ECM detects that the increment of engine coolant temperature depend on the MAF sensor.

• | Once the above condition exists for about 500 seconds. DTC P0116 runs continuously.

### Conditions for Setting the DTC

• | Once the above conditions are met, and the ignition switch is turned to ON position, the ECM detects the difference between ECT and IAT are not within the last ignition cycle procedure recorded of 10°C (18°F).

| OR

• | The ECM detects the difference between the modeled ECT and the actual measured ECT is more than 9.8°C (18°F).

• | The above condition exists for more than 4 seconds.

### Action Taken When the DTC Sets

• | Do not illuminate MIL.

• | The ECM records the operating conditions at the time when the diagnostic test fails. The ECM displays the failure information in the Failure Records on the scan tool.

### Conditions for Clearing the MIL/DTC

• | The DTC becomes history when the conditions for setting the DTC are no longer present.

• | The history DTC is cleared after 40 malfunction free warm-up cycles.

• | The ECM receives the clear code command from the scan tool.

### Diagnostic Aids

• | Test the ECT and IAT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor can result in a DTC or a driveability condition. Refer to Temperature Versus Resistance - Engine Coolant Temperature Sensor and Temperature Versus Resistance - Intake Air Temperature Sensor .

• | If the vehicle has set overnight, the IAT sensor and the ECT sensor values should display within 3°C (5°F).

• | Start the engine when it is cold, the ECT sensor temperature should rise steadily, then stabilize after the thermostat opens.

• | High resistance in the circuits of either the ECT or IAT sensor could set a DTC.

• | A short to ground or voltage through a conductive material or fuel could set this DTC. Inspect the ECT sensor for evidence of coolant leaking into the connector body.

• | The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to Front of Vehicle/Engine Compartment Component Views.

• | Use the J 35616-A/BT-8637 Connector Test Adapter Kit for any test that requires probing the underhood fuse block terminals, component wire harness terminals, or the ECM wire harness connector terminals.

• | For an intermittent condition, refer to Intermittent Conditions.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics Connector End View Reference: Component Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Is DTC P0101, P0117, P0118 or P0119 also set? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle | Go to Step 3
3 |

1. Inspect the engine coolant level.
2. Verify the operation of cooling system.

Is there a susceptible condition with engine cooling system?

--

Go to Symptoms - Engine Cooling

Go to Step 4

4 |

1. Observe the Freeze Frame/Failure Records for this DTC.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. 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.

Did the DTC fail this ignition?

--

Go to Step 5

Go to Diagnostic Aids

5 |

1. Turn the ignition switch to OFF position, disconnect the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement.
2. Turn the ignition switch to ON position, with the engine OFF.
3. Observe the engine coolant temperature (ECT) sensor parameter with a scan tool.

Is the temperature less than the specified value?

-40°C (-40°F)

Go to Step 7

Go to Step 6

6 |

1. Turn the ignition switch to OFF position, disconnect the engine control module (ECM).
2. Check the signal circuit of the ECT sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 12

7 |

1. Turn the ignition switch to OFF position.
2. Remove the ECM/TCM fuse from the underhood electrical center.

Note: The control module or the sensor may be damaged if the circuit is shorted to battery positive voltage.

3. Measure the resistance between the low reference circuit of the ECT sensor and the ECM housing with a DMM.

Is the resistance less than the specified value?

5 Ω

Go to Step 8

Go to Step 9

8 |

1. Turn the ignition switch to OFF position, install the ECM/TCM fuse into the underhood fuse block.
2. Turn the ignition switch to ON position, install a 3-amp fused jumper between the signal circuit of the ECT sensor and the low reference circuit.
3. Observe the engine coolant temperature (ECT) sensor parameter with a scan tool.

Is the temperature more than the specified value?

142°C (288°F)

Go to Step 11

Go to Step 10

9 | Test the low reference circuit of the ECT sensor for an open, a high resistance or a short to voltage. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12
10 | Test the signal circuit of the ECT sensor for a short to voltage, an open or a high resistance. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12
11 | Test for shorted terminals and poor connections at the ECT sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 13
12 | Test for shorted terminals and for poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14
13 | Replace engine coolant temperature (ECT) sensor. Refer to Engine Coolant Temperature Sensor Replacement. Did you complete the replacement? | -- | Go to Step 15 | --
14 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 15 | --
15 |

1. Clear any DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. 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.

Does the DTC fail this ignition?

--

Go to Step 2

Go to Step 16

16 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK