For 1990-2009 cars
Engine Controls Components
Engine Controls Schematics
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The engine coolant temperature (ECT) sensor is a thermistor mounted in the engine coolant stream. The PCM applies a voltage (about 5.0 volts) through a pull up resistor to the ECT signal circuit. When the engine coolant is cold, the sensor (thermistor) resistance is high. Therefore the PCM will measure a high signal voltage. As the engine coolant warms, the sensor resistance becomes less, and the ECT signal voltage measured at the PCM drops. With a fully warmed up engine, the ECT signal voltage should measure about 1.5 to 2.0 volts. If the PCM detects an ECT signal that is intermittently above the range of the ECT sensor, DTC P1115 will set.

### Conditions for Running the DTC

The engine is running for 15 seconds.

### Conditions for Setting the DTC

• | The ECT sensor is intermittently less than -39°C (-37°F)

• | Above conditions present for longer than 3 seconds.

### Action Taken When the DTC Sets

The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.

### Conditions for Clearing the MIL/DTC

• | The DTC becomes history when the conditions for setting the DTC are no longer present.

• | The history DTC clears after 40 malfunction free warm-up cycles.

• | The PCM receives a clear code command from the scan tool.

### Diagnostic Aids

The following could cause an intermittent condition:

Many situations may lead to an intermittent condition. Perform each inspection or test as directed.

Important: : Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

• | Loose terminal connection

- | Use a corresponding mating terminal to test for proper tension. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair.

- | Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair.

• | Damaged harness--Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair.

• | Inspect the powertrain control module (PCM) and the engine grounds for clean and secure connections. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair.

If the condition is determined to be intermittent, reviewing the Snapshot or Freeze Frame/Failure Records may be useful in determining when the DTC or condition was identified.

#### DTC P1115 - ECT Sensor Circuit Intermittent High Voltage

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | With a scan tool, select Diagnostic Trouble Codes (DTC). Does the scan tool indicate DTC P0118 also set? | -- | Go to DTC P0108 Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage | Go to Step 3
3 | Is DTC P1106, P1111, and/or P1121 also set? | -- | Go to Step 8 | Go to Step 4
4 | Inspect for a faulty ground circuit connection 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 10 | Go to Step 5
5 | Inspect for a faulty signal circuit connection 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 10 | Go to Step 6
6 | Test the signal circuit of the ECT sensor for an intermittent open. 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 10 | Go to Step 7
7 | Test the signal circuit of the ECT sensor for an intermittent short to voltage. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 8
8 | Inspect for a faulty sensor ground circuit connection at the PCM. 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 10 | Go to Step 9
9 | Test the ground circuit of the ECT sensor for an intermittent open or a faulty splice. 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 10 | Go to Diagnostic Aids
10 |

1. Use the scan tool in order to clear the DTCs.
2. Operate the vehicle within the Fail Record conditions as noted.

Does the DTC reset?

--

Go to Step 2

System OK