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 ECT signal circuit and a ground for the ECT low reference circuit. When the ECT is cold, the sensor resistance is high. When the ECT increases, the sensor resistance lowers. With high sensor resistance, the PCM detects a high voltage on the ECT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the ECT signal circuit. If the PCM detects an excessively high signal voltage, which is a low temperature indication, DTC P1115 sets.
Conditions for Running the DTC
The engine run time is more than 5 seconds.
Conditions for Setting the DTC
The PCM detects an intermittent low ECT sensor temperature while the engine is running and run time exceeds 5 seconds.
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
| • | An ECT sensor or PCM which is intermittently shorted, open, or skewed is possible yet very unlikely. |
| • | An intermittent open or short to voltage in the ECT sensor signal circuit could result in a DTC P1115. If the high ECT voltage (low temperature) reading is present, additional sensor circuit voltage codes could be set. Refer to any non-intermittent DTCs that are set. |
| • | Use the Temperature vs. Resistance Value scale in order to test the coolant sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor could result in poor driveability complaints. Refer to Temperature Versus Resistance . |
| • | If an intermittent condition is suspected, refer to Intermittent Conditions . |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics | |||
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | |
2 |
Does the scan tool indicate that DTC P0118 also failed? | Go to DTC P0118 | Go to Step 3 |
3 |
Does the scan tool indicate an abrupt change in value? | Go to Step 6 | Go to Step 4 |
4 |
Does the scan tool indicate an abrupt change in value? | Go to Step 7 | Go to Step 5 |
Does the DTC reset ? | Go to Diagnostic Aids | System OK | |
6 | Repair the connector or terminal as necessary. Refer to Circuit Testing and Connector Repairs in Wiring Systems. Did you complete the repair? | Go to Step 8 | -- |
7 | Repair the harness or wiring as necessary. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 8 | -- |
8 |
Does the DTC run and pass? | Go to Step 9 | Go to Step 2 |
9 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | System OK | |
