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 decreases. 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.
DTC Descriptor
This diagnostic procedure 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 60 seconds. |
| OR |
| • | The engine run time is less than 60 seconds when the intake air temperature (IAT) is more than 0°C (32°F). |
| • | DTC P1115 runs continuously when the above condition is met. |
Conditions for Setting the DTC
The PCM detects that the ECT sensor parameter is less than -38°C (-36°F) intermittently for a calibrated amount of time.
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, but very unlikely. |
| • | An intermittent open or a short to voltage in the ECT sensor signal circuit could result in DTC P1115 setting. Refer to Intermittent Conditions . |
| • | Use the Temperature vs. Resistance Value table to test the coolant sensor at various temperature levels to evaluate the possibility of a skewed sensor. A skewed sensor could result in poor driveability conditions. Refer to Temperature Versus Resistance . |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 | Observe the DTC information with a scan tool. Is DTC P0118 set? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 3 |
3 |
Does the scan tool indicate an abrupt change in value? | Go to Step 6 | Go to Step 4 |
4 | Observe the ECT parameter with a scan tool while moving the wiring harness at the ECT sensor and the PCM. Refer to Inducing Intermittent Fault Conditions in Wiring Systems. Does the scan tool indicate an abrupt change in value? | Go to Step 7 | Go to Step 5 |
5 |
Did the DTC fail this ignition? | Go to Step 2 | System OK |
6 | Repair the ECT connector or the terminal as necessary. Refer to Connector Repairs in Wiring Systems. Did you complete the repair? | Go to Step 8 | -- |
7 | Repair the wiring harness or the wiring as necessary. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 8 | -- |
8 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 9 |
9 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK |
