P0116

DTC P0116

DTC DESCRIPTOR

DTC P0116
Engine Coolant Temperature (ECT) Sensor Performance

DIAGNOSTIC FAULT INFORMATION






IMPORTANT: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

TYPICAL SCAN TOOL DATA

ECT Sensor Temperature:

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 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 the intake air temperature (IAT). Before failing this diagnostic, the ECM will perform the calculation to determine the presence of a block heater.

CONDITIONS FOR RUNNING THE DTC
- DTC 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 of more than 5.3°C (41.5°F), the vehicle must be driven for more than 360 seconds over 24 km/h (15 mph). If the IAT sensor temperature decreases more than 5.3°C (41.5°F), a block heater is detected and the test is aborted. If the IAT sensor 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 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 data before it changes.
- An IAT sensor 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.

CIRCUIT/SYSTEM VERIFICATION
1. If the ignition has been OFF for 10 hours or more, the ECT and the IAT 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 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.
2. An IAT sensor 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 at various ambient temperatures, then compare those measurements to the Temperature vs. Resistance table. Refer to Temperature vs Resistance (ECT Sensor), Temperature vs Resistance (IAT Sensor), Temperature vs Resistance (IAT 2 Sensor), Temperature vs Resistance (Fuel Temperature).
3. Use the scan tool Ignition OFF parameter and a watch to determine if the internal clock of the ECM is working properly.
4. Inspect the ECT sensor terminals for corrosion and for engine coolant leaking through the sensor.
5. Turn OFF the ignition.

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.

6. Inspect the cooling system surge tank for the proper engine coolant level. Refer to Cooling System Leak Testing and Draining and Filling Cooling System.

IMPORTANT:
- The engine needs to have been OFF for at least 10 hours for the ECT and the IAT to be at ambient temperature. The vehicle should not have changed environments during this time.
- The IAT sensor will start to warm-up as soon as the ignition is turned ON.

1. Set up the scan tool to take a snapshot of engine data.
2. Turn on the ignition.
3. Take snapshot with the scan tool.
4. The difference between the ECT parameter and the IAT parameter should be less than 6°C (11°F).

CIRCUIT/SYSTEM TESTING
1. Disconnect the ECT sensor.
2. Turn ON the ignition, with the engine OFF.
3. Measure for the proper voltage range of 4.9-5.2 volts between the ECT signal circuit and a good ground with a DMM.
- If the voltage is less than 4.9 volts, test the ECT sensor signal circuit for a high resistance short to ground or a faulty ECM.
4. Remove and test the ECT sensor.
- If the resistance measurements of the ECT sensor are out of range, replace the sensor.
- If the ECT sensor tests normal and the DTC continues to set, replace the ECM.

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.

REPAIR INSTRUCTIONS

IMPORTANT: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- Engine Coolant Temperature (ECT) Sensor Replacement
- Control Module References for engine control module (ECM) replacement, setup, and programming