Circuit Description
The engine coolant temperature (ECT) sensor is a variable resistor, that measures the temperature of the engine coolant. The ECT sensor has a signal circuit and a low reference circuit. The engine control module (ECM) 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 ECM detects a high voltage on the ECT signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the ECT signal circuit. If the ECM detects an excessively high ECT 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 is running for more than one minute. |
| OR |
| • | The engine run time is less than one minute when the intake air temperature (IAT) is more than -7°C (+19°F). |
| • | This DTC runs continuously within the enabling conditions. |
Conditions for Setting the DTC
The ECM detects that the ECT sensor parameter is less than -39°C (-38°F) intermittently for more than 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. |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Engine Control Module Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Important: The cooling fans will be commanded ON when certain engine coolant temperature (ECT) DTCs are set. Observe the ECT sensor parameter with a scan tool. Is the ECT sensor parameter less than the specified value? | -39°C (-38°F) | Go to Step 4 | Go to Step 3 |
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Testing for Intermittent Conditions and Poor Connections |
4 |
Is the voltage more than the specified value? | 5.2 V | Go to Step 5 | Go to Step 6 |
5 |
Important: If a short to voltage occurs, the ECT sensor may be damaged. Test the ECT signal circuit for an intermittent short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12 |
6 |
Is the ECT sensor parameter more than the specified value? | 149°C (300°F) | Go to Step 10 | Go to Step 7 |
7 |
Is the ECT sensor parameter more than the specified value? | 149°C (300°F) | Go to Step 9 | Go to Step 8 |
8 | Test the signal circuit of the ECT sensor for an intermittent high resistance or an open. Refer to Circuit Testing , Inducing Intermittent Fault Conditions , and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12 |
9 | Test the ECT sensor low reference circuit for an intermittent high resistance or an open. Refer to Circuit Testing , Inducing Intermittent Fault Conditions , and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12 |
10 | Test the ECT signal circuit for an intermittent short to any 5-volt reference circuit. Refer to Circuit Testing , Inducing Intermittent Fault Conditions , and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 11 |
11 | Test for an intermittent and for a poor connection at the ECT sensor. Refer to Testing for Intermittent Conditions and Poor Connections , Inducing Intermittent Fault Conditions , and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 13 |
12 | Test for an intermittent and for a poor connection at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections , Inducing Intermittent Fault Conditions , and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14 |
13 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- |
14 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 15 | -- |
15 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 16 |
16 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
