• | 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. |
Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance |
---|---|---|---|---|---|
ECT Sensor Signal | P0117 | P0118 | P0118 | P0118 | P0116, P0125, P0128 |
Low Reference | -- | P0118 | P0118 | P0118 | P0125, P0128 |
Circuit | Normal Range | Short to Ground | Open | Short to Voltage |
---|---|---|---|---|
ECT Sensor Signal | -39 to +120°C (-38 to +248°F) | 150°C (303°F) | -40°C (-40°F) | -40°C (-40°F) |
Low Reference | -- | -- | -40°C (-40°F) | -40°C (-40°F) |
The engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The control module 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 control module uses this High Side Coolant Rationality test to determine if the ECT input is skewed high. The internal clock of the control module will record the amount of time the ignition is OFF. At restart, the control module will compare the temperature difference between the ECT and the intake air temperature (IAT). Before failing this test, the control module will perform a calculation to determine the presence of an engine block heater. If the control module detects that the temperature difference between the ECT and the IAT is not within the calibrated range after the ignition OFF time, DTC P0116 sets.
An ECT sensor monitors the temperature of the coolant. This input is used by the control module for engine control and as an enabling criteria for some diagnostics. The air flow into the engine is accumulated and used to determine if the vehicle has been driven within the conditions that would allow the engine coolant to heat up normally to the Closed Loop temperature. If the coolant temperature does not increase normally or does not reach the Closed Loop temperature, the diagnostics that use engine coolant temperature as enabling criteria may not run when expected. If the control module detects the calibrated amount of air flow and engine run time have been met, and the engine coolant has not met the Closed Loop temperature, DTC P0125 sets.
An ECT sensor monitors the temperature of the coolant. This input is used by the control module for engine control and as an enabling criteria for some diagnostics. The air flow coming into the engine is accumulated and used to determine if the vehicle has been driven within the conditions that would allow the engine coolant to heat up normally to the thermostat regulating temperature. If the coolant temperature does not increase normally or does not reach the regulating temperature of the thermostat, the diagnostics that use ECT as enabling criteria may not run when expected. If the control module detects the calibrated amount of air flow and engine run time have been met, and the ECT has not met the minimum thermostat regulating temperature, DTC P0128 sets.
• | DTCs P0112, P0113, P0117, P0118, P0502, P0503, P0601, P0602, P0604, P0606, P2610 are not set. |
• | The ignition is ON. |
• | The IAT parameter is more than 15°C (59°F). |
• | The Fuel Level Sensor parameter is more than 10 percent. |
• | The vehicle has a minimum ignition OFF time of 8 hours. |
• | This diagnostic runs once per ignition cycle when the above conditions are met. |
• | DTCs P0101, P0102, P0103, P0112, P0113, P0117, P0118, P0502, or P0503 are not set. |
• | The minimum air temperature is more than -7°C (+19°F). |
• | The start-up ECT is less than 10°C (50°F). |
• | The engine run time is between 30-1,800 seconds. |
• | The vehicle has traveled more than 0.8 kilometer (0.5 mile) at more than 8 km/h (5 mph). |
• | This diagnostic runs once per ignition cycle when the above conditions are met. |
• | DTCs P0101, P0102, P0103, P0112, P0113, P0117, P0118, P0502, or P0503 are not present. |
• | The startup ECT is less than 75°C (167°F). |
• | The IAT is more than -7°C (+19°F). |
• | The engine run time is between 30-1,800 seconds. |
• | The vehicle is driven more than 0.8 kilometer (0.5 mile) at more than 8 km/h (5 mph). |
• | This diagnostic runs once per ignition cycle when the above conditions are met. |
• | The control module detects a temperature difference between the ECT sensor and the IAT sensor of more than 100°C (180°F) at start up. |
OR |
• | The control module detects a temperature difference between the ECT sensor and the IAT sensor of more than 15°C (27°F) and the time elapsed cranking the engine without starting is more than 5 seconds. |
OR |
• | The control module detects a temperature difference between the ECT sensor and the IAT sensor of more than 15°C (27°F). The vehicle must then be driven for 5 minutes over 40 km/h (25 mph). If the IAT sensor temperature decreases more than 5°C (9°F), an engine block heater was detected and the test is aborted. If the IAT sensor temperature does not decrease, an engine block heater was not detected and DTC P0116 will set. |
The control module detects that the actual amount of accumulated airflow is more than the predicted amount of accumulated air flow before the ECT reaches 15°C (59°F).
The control module detects that the actual amount of accumulated air flow is more than the predicted amount of accumulated air flow before the ECT reaches 80°C (176°F).
DTC P0116 P0125 and P0128 are Type B DTCs.
DTC P0116 P0125 and P0128 are Type B DTCs.
• | Circuit Testing |
• | Wiring Repairs |
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.
Important: A critical analysis of the operation of the thermostat is necessary, to properly diagnose these DTCs.
Important:
• | For P0116 only, the vehicle should be OFF for at least 8 hours for the ECT and the IAT to be at ambient temperature. The vehicle should not have changed environments during this time. |
• | The cooling fans are commanded ON when certain ECT DTCs are set. |
• | The cooling system coolant level--Refer to Loss of Coolant . |
• | Corrosion on the ECT terminals |
• | Improper or corroded terminals at the ECT harness connector |
• | Loose terminals in the ECT harness connector |
• | The ECT sensor for leaking engine coolant internally through the sensor |
⇒ | If not within 4.8-5.2 volts, test the ECT sensor signal circuit for high resistance, or for an intermittent or poor connection at the control module. If circuits test OK, then replace the control module. |
⇒ | If not within 4.8-5.2 volts, test the ECT sensor low reference circuit for high resistance, or for an intermittent or poor connection at the control module. If circuits test OK, then replace the control module. |
⇒ | If not within 4.8-5.2 volts, test the IAT signal circuit for high resistance, or for an intermittent or poor connection at the control module. If circuits test OK, then replace the control module. |
⇒ | If more than 5 ohms, test the IAT low reference circuit for high resistance or for an intermittent or poor connection at the control module. If circuits test OK, then replace the control module. |
Important: The IAT sensor will start to warm-up as soon as the ignition is turned ON.
⇒ | If more than 8°C (14°F), replace the IAT sensor. |
⇒ | If more than 15°C (27°F), replace the ECT sensor. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for powertrain control module (PCM) replacement, setup, and programming |