For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptors

DTC P1114: Engine Coolant Temperature (ECT) Sensor Circuit Intermittent Low Voltage
DTC P1115: Engine Coolant Temperature (ECT) Sensor Circuit Intermittent High Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
ECT Sensor Signal | P0117, P1114 | P0118, P1115 | P0118, P1115* | P0115
Low Reference | -- | P0118, P1115 | -- | P0115
* Internal ECM damage may occur if the circuit is shorted to B+

### Typical Scan Tool Data

#### ECT Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: Engine operating in Closed Loop. Parameter Normal Range: Varies with ambient temperature.
ECT Sensor Signal | 129°C (264°F), 0.0 Volts | -40°C (-40°F), 5.0 Volts | -40°C (-40°F), 5.0 Volts*
Low Reference | -- | -40°C (-40°F), 5.0 Volts | --
* Internal ECM damage may occur if the circuit is shorted to B+

### 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.

The following table illustrates the difference between temperature, resistance, and voltage:

ECT | ECT Resistance | ECT Signal Voltage
--- | --- | ---
Cold | High | High
Warm | Low | Low

### Conditions for Running the DTC

• | The engine has been running for more than 2 minutes.

• | The DTCs run continuously when the above condition is met.

### Conditions for Setting the DTC

#### P1114

The ECM detects that the ECT sensor is more than 149°C (300°F ) intermittently.

#### P1115

The ECM detects that the ECT sensor is less than -38°C (-34°F) intermittently.

### Action Taken When the DTC Sets

DTCs P1114 and P1115 are Type C DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P1114 and P1115 are Type C DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Engine running, observe the DTC Information with a scan tool. DTCs P0117, or P0118 should not set.

⇒ | If any DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.

2. Observe the DTC Information with a scan tool. DTCs P1114 or P1115 should not set.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

Engine running, observe the scan tool engine coolant temperature (ECT) sensor parameter while moving the related wiring harness and harness connectors. The reading should not change abruptly.

⇒ | If the reading changes abruptly, repair the wiring harness and harness connectors.

### Component Testing

1. Ignition OFF, disconnect the harness connector at the ECT sensor.

Important: A thermometer can be used to the used to test the sensor off the vehicle.

2. Test the ECT sensor by varying the sensor temperature while monitoring the sensor resistance. Compare the readings with the Temperature Versus Resistance table and verify the resistance is within 5 percent of the specification.

⇒ | If not within the specified range, replace the ECT sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Engine Coolant Temperature Sensor Replacement

• | Control Module References for ECM replacement, setup, and programming