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 ECT signal circuit and supplies a ground to the low reference circuit. If the ECM detects that the ECT signal made an excessive and abrupt change, this DTC sets.
The following table illustrates the difference between temperature, resistance, and voltage:
ECT | ECT Resistance | ECT Signal Voltage |
|---|---|---|
Cold | High | High |
Warm | Low | Low |
DTC Descriptor
This diagnostic supports the following DTC:
DTC P0119 Engine Coolant Temperature (ECT) Sensor Circuit Intermittent
Conditions for Running the DTC
| • | The engine is running. |
| • | This DTC runs continuously once the above condition is met. |
Conditions for Setting the DTC
The ECM detects that the ECT sensor signal value has changed more than 7.5°C (45.5°F) in less than 5 seconds.
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
| • | Test the ECT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor can result in a driveability condition. |
| • | After starting the engine, the ECT sensor temperature should rise steadily, then stabilize after the thermostat opens. |
| • | A high resistance on the ECT signal circuit or the ECT low reference circuit may not set a DTC. Refer to Circuit Testing in Wiring Systems. |
| • | If the vehicle has set overnight, the ECT sensor and the intake air temperature (IAT) sensor values should display within 3°C (5°F). Refer to Temperature Versus Resistance . |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for excessive resistance in the ECT circuit.
-
This step isolates the condition. If the temperature changes, test for a condition in the low reference circuit. If the temperature remains the same, test the signal circuit for a condition.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connect End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | |
2 |
Is DTC P0117 or P0118 also set? | -- | Go to Step 3 | |
3 | Observe the ECT sensor parameter with a scan tool while moving the ECT sensor connector and the engine control module (ECM) connector. Refer to Inducing Intermittent Fault Conditions in Wiring Systems. Does the scan tool indicate an abrupt change in value? | -- | Go to Step 11 | Go to Step 4 |
4 | Observe the ECT sensor parameter with a scan tool while moving the wiring harness between the ECT sensor and the ECM. Refer to Inducing Intermittent Fault Conditions in Wiring Systems. Does the scan tool indicate an abrupt change in value? | -- | Go to Step 11 | Go to Step 5 |
Is the temperature at the specified value? | 129°C (264°F) | Go to Step 9 | Go to Step 6 | |
Is the temperature at the specified value? | 129°C (264°F) | Go to Step 7 | Go to Step 8 | |
7 | Test the low reference circuit of the ECT sensor for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 10 |
8 | Test the signal circuit of the ECT sensor for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 10 |
9 | Test for shorted terminals and poor connections at the ECT 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 14 | Go to Step 12 |
10 | Test for shorted terminals and poor connections at the 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 14 | Go to Step 13 |
11 | Repair the connector/terminal or circuits as necessary. Refer to Connector Repairs or Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 14 | -- |
12 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . | -- | Go to Step 14 | -- |
13 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
14 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 15 |
15 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
