GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Engine 🢒 Engine Controls - 6.6L (LLY) 🢒 DTC P0116

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 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 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 perform the calculation to determine 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.

DTC Descriptor

This diagnostic supports the following DTC:

DTC P0116 Engine Coolant Temperature (ECT) Sensor Performance

Conditions for Running the DTC
    • DTCs P0112, P0113, P0117, P0118, P0500, P2610 are not set.
    • The ignition is ON.
    • The start-up IAT is more than 15°C (59°F).
    • The vehicle has a minimum engine OFF time of 10 hours.
    • DTC P0116 runs once per drive cycle within the enabling conditions.

Conditions for Setting the DTC

If the ECM detects a start-up temperature difference between the ECT sensor and the IAT sensor of more than 5°C (9°F), then the vehicle must be driven for more than 400 seconds over 24 km/h (15 mph) and the engine speed must be more than 600 RPM. 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 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.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. A snapshot is the quickest method to capture the data before it changes.

    2.

  2. An IAT sensor that is skewed low can cause this DTC to set.

    3.

  3. This step will determine if high resistance has caused this DTC to set.

    4.

  4. 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

Go to Diagnostic System Check - Engine Controls

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

  1. Remove the mass air flow/intake air temperature (MAF/IAT) sensor. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement .
  2. Remove the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement .
  3. Place the sensors on a work surface away from any heat source.
  4. Allow the sensors to reach the ambient air temperature for 30-60 minutes.

Are the sensors at the ambient temperature?

--

Go to Step 6

--

6
  1. Connect the MAF/IAT sensor to the electrical connector, but DO NOT install it.
  2. Insulate the sensor from any engine heat source.
  3. Connect the ECT sensor to the electrical connector, but DO NOT install it.
  4. Insulate the sensor from any engine heat source.

Are the sensors connected?

--

Go to Step 7

--

7

Important: The IAT sensor will start to warm-up as soon as the ignition is turned ON.

  1. Turn ON the ignition.
  2. Take a snapshot of the Engine Data List with a scan tool. Refer to Scan Tool Snapshot Procedure in Wiring Systems.
  3. Review the snapshot data that was taken with the scan tool.
  4. Observe the ECT Sensor parameter with a scan tool.
  5. Observe the IAT Sensor parameter with a scan tool.

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

8

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

10

  1. Disconnect the MAF/IAT sensor.
  2. Test for an intermittent and for a poor connection at the IAT 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 25

Go to Step 11

11
  1. At the sensor, measure the resistance between the IAT signal and the IAT low reference terminals with a DMM and record the value. Refer to Circuit Testing in Wiring Systems.
  2. Observe the recorded ambient air temperature.
  3. Compare the resistance measurement of the IAT sensor to the ambient air temperature using the Temperature vs. Resistance table. Refer to Temperature Versus Resistance .

Is the resistance measurement of the IAT sensor within the specified range?

--

Go to Step 14

Go to Step 22

12

  1. Disconnect the ECT sensor.
  2. Inspect for the following conditions:
    3. • An ECT sensor leaking engine coolant internally through the sensor
    • Corrosion on the ECT sensor terminals
    • Corrosion on the ECT harness connector terminals--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 13

13

    Important: Do not hold the ECT sensor by the probe.

  1. At the sensor, measure the resistance between the ECT signal and the ECT low reference terminals with a DMM and record the value. Refer to Circuit Testing in Wiring Systems.
  2. Observe the recorded ambient air temperature.
  3. Compare the resistance measurement of the ECT sensor to the ambient air temperature using the Temperature vs. Resistance table. Refer to Temperature Versus Resistance .

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.

  1. Turn OFF the ignition for 90 seconds to allow the control modules to power down.
  2. Measure the resistance from the low reference circuit of the IAT sensor to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.

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 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.

  1. Clear the DTCs with a scan tool.
  2. Turn OFF the engine for 10 hours.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running in 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 2

Go to Step 27

27

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK