P0116

DTC P0116

CIRCUIT DESCRIPTION
The engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The powertrain control module (PCM) supplies 5 volts to the signal circuit and a ground for the ECT low reference circuit. When the ECT is low, the sensor resistance is high. When the ECT is high, the sensor resistance is low. The PCM uses this high side coolant rationality test to determine if the ECT input is skewed high. The internal clock of the PCM will record the amount of time the ignition is OFF. At restart, the PCM will compare the temperature difference between the ECT and the intake air temperature (IAT). Before failing this test, the PCM will perform a calculation to determine the presence of a block heater. If the PCM detects that the temperature difference is not within the calibrated range after the ignition OFF time, DTC P0116 sets.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P0116 Engine Coolant Temperature (ECT) Sensor Performance

CONDITIONS FOR RUNNING THE DTC
- The ignition is ON.
- DTCs P0112, P0113, P0116, P0117, P0118, P0128, P0502, P0503 are not set.
- The start-up IAT is more than -7°C (+20°F).
- The vehicle has a minimum ignition OFF time of 10 hours.
- DTC P0116 runs once per drive cycle when the above conditions are met.

CONDITIONS FOR SETTING THE DTC
- The start-up ECT is more than the start-up IAT by 100°C (180°F). OR
- The start-up ECT is more than the start-up IAT by 15°C (27°F), then the vehicle must be driven for more than 400 seconds over 24 km/h (15 mph). If the IAT sensor temperature decreases more than 8°C (14°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.

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.

DIAGNOSTIC AIDS
DTC P0116 may set if the vehicle uses an aftermarket engine block heater.

TEST DESCRIPTION

Steps 1 - 9:

Steps 10 - 17:

Steps 18 - 27:

The numbers below refer to the step numbers on the diagnostic table.
7. A snapshot is the quickest method to capture the data before it changes.
8. An IAT sensor that is skewed low can cause this DTC to set.
10. This step will determine if high resistance has caused this DTC to set.
12. A high resistance short from the signal circuit to the low reference circuit can cause this DTC to set.