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 low reference circuit. When coolant temperatures are low, resistance is high. When 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 high. 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 intake air temperature (IAT). Before failing this diagnostic, the ECM will test for the presence of a block heater. If the temperature difference is not within the calculated range, after the predetermined engine OFF time, DTC P0116 sets.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The start-up IAT is more than 15°C (59°F). |
| • | DTCs P0112, P0113, P0117, P0118, P0500, P1683 are not set. |
| • | The vehicle has a minimum engine off time of 10 hours. |
Conditions for Setting the DTC
If the ECM detects a temperature difference between the ECT sensor and the IAT sensor of more than 5°C (9°F), then the vehicle must be driven for 400 seconds over 24 km/h (15 mph). If the IAT sensor temperature decreases more than 5°C (9°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 stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records. |
| • | The driver information center, if equipped, may display a message. |
Conditions for Clearing the DTC
| • | 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 non-emission related diagnostic. |
| • | Clear the DTC with a scan tool. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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A snapshot is the quickest method to capture the data before it changes.
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An IAT sensor that is skewed low can cause this DTC to set.
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This step will determine if high resistance has caused this DTC to set.
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A high resistance short from the signal circuit to the low reference circuit can cause this DTC to set.
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 | Inspect the cooling system coolant level. Is the cooling system coolant low? | -- | Go to Cooling System Draining and Filling in Engine Cooling | Go to Step 3 | ||||||
3 | Observe and record the ambient air temperature of the vehicle environment using an accurate thermometer. Did you complete the action? | -- | Go to Step 4 | -- | ||||||
4 |
Important: The engine needs to have been OFF for at least 10 hours for the engine coolant temperature (ECT) and the intake air temperature (IAT) to be at ambient temperature. The vehicle should not have changed environments during this time. Has the engine been OFF for the specified amount of time? | 10 hrs | Go to Step 7 | Go to Step 5 | ||||||
5 |
Are the sensors at the ambient temperature? | -- | Go to Step 6 | -- | ||||||
6 |
Are the sensors connected? | -- | Go to Step 7 | -- | ||||||
|
Important: The IAT sensor will start to warm-up as soon as the ignition is turned ON.
Is the difference between the ECT Sensor parameter and the IAT Sensor parameter more than the specified value? | 5°C (9°F) | Go to Step 8 | Go to Intermittent Conditions | |||||||
Observe the recorded IAT Sensor parameter. Is the difference between the IAT Sensor parameter and the ambient air temperature less than the specified value? | 5°C (9°F) | Go to Step 9 | Go to Step 10 | |||||||
9 | Observe the recorded ECT Sensor parameter. Is the difference between the ECT Sensor parameter and the ambient air temperature less than the specified value? | 5°C (9°F) | Go to Intermittent Conditions | Go to Step 12 | ||||||
Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 11 | |||||||
11 |
Is the resistance measurement of the IAT sensor within the specified range? | -- | Go to Step 14 | Go to Step 22 | ||||||
Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 13 | |||||||
13 |
Is the resistance measurement of the ECT sensor within the specified range? | -- | Go to Step 15 | Go to Step 23 | ||||||
14 | Measure the voltage from the IAT signal circuit to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems. Is the voltage within the specified range? | 4.8-5.2 V | Go to Step 16 | Go to Step 17 | ||||||
15 | Measure the voltage from the ECT signal circuit to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems. Is the voltage within the specified range? | 4.8-5.2 V | Go to Intermittent Conditions | Go to Step 19 | ||||||
16 |
Important: All electrical components and accessories must be turned OFF. Performing this step will disable the diagnostic for 10 hours.
Is the resistance less than the specified value? | 5 ohms | Go to Intermittent Conditions | Go to Step 18 | ||||||
17 | Test the IAT signal circuit for a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 20 | ||||||
18 | Test the IAT low reference circuit for a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 20 | ||||||
19 | Test the ECT signal circuit for a high resistance or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 21 | ||||||
20 | 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 25 | Go to Step 24 | ||||||
21 | Test for shorted terminals and poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs in Wiring Systems, and Intermittent Conditions . Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 24 | ||||||
22 | Replace the MAF/IAT sensor. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 25 | -- | ||||||
23 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 25 | -- | ||||||
24 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 25 | -- | ||||||
25 | Reassemble the vehicle as necessary. Did you complete the action? | -- | Go to Step 26 | -- | ||||||
26 |
Important: This DTC will not run without the engine being OFF for at least 10 hours.
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 27 | ||||||
27 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||
