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 an intermittent high ECT signal voltage, which is a low temperature indication, 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 P1115 Engine Coolant Temperature (ECT) Sensor Circuit Intermittent High Voltage
Conditions for Running the DTC
| • | The engine run time is more than 120 seconds. |
| • | This DTC runs continuously once the above condition is met. |
Conditions for Setting the DTC
The ECM detects that the engine coolant temperature is less than -38°C (-36°F) intermittently.
Action Taken When the DTC Sets
| • | The control module stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records. |
| • | The driver information center, if equipped, may display a message. |
Conditions for Clearing the DTC
| • | 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 non-emission related diagnostic. |
| • | Clear 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. |
| • | 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 . |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Engine Controls? | Go to Step 2 | |
2 | Observe the DTC information with a scan tool. Is DTC P0118 set? | Go to DTC P0118 | Go to Step 3 |
3 | Observe the engine coolant temperature (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 5 | 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 6 | Go to Diagnostic Aids |
5 | Repair the connector/terminal as necessary. Refer to Connector Repairs in Wiring Systems. Did you complete the repair? | Go to Step 7 | -- |
6 | Repair the harness/wiring as necessary. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 7 | -- |
7 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 8 |
8 | Observe the Capture Info with a scan tool. Does the scan tool display any DTCs that have not been diagnosed? | System OK | |
