Service Information

Cruze

DTC P0115

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 P0115 03: Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage

DTC P0115 07: Engine Coolant Temperature (ECT) Sensor Circuit High Voltage

Typical Scan Tool Data

ECT Sensor

Circuit	Short to Ground	Open	Short to Voltage
Operating Conditions: Engine operating in Closed Loop. Parameter Normal Range: -39 to +142°C (-38 to +288°F) Varies with coolant temperature.
ECT Sensor Signal	149°C (300°F)	-40°C (-40°F)	-40°C (-40°F)*
Low Reference	-	-40°C (-40°F)	-40°C (-40°F)*
* Internal ECM or ECT sensor damage may occur if the circuit is shorted to B+

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 V to the ECT signal circuit and supplies an ground to the low reference circuit.

Temperature vs. Resistance and Voltage

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 ignition is ON.

Conditions for Setting the DTC

P0115 03

The ECM detects the ECT voltage is less than 117 mV for greater than 1 s.

P0115 07

The ECM detects the ECT voltage is greater than 4.96 V for greater than 1 s.

Action Taken When the DTC Sets

DTC P0115 is a Type B DTC.

Conditions for Clearing the DTC

DTC P0115 is a Type B DTC.

Diagnostic Aids

•	Test the ECT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor can result in a DTC or a driveability condition. Refer to Temperature Versus Resistance .

•	If the engine has sat overnight, the intake air temperature sensor (IAT) and the ECT sensor values should display within 3°C (5°F).

•	After starting a cold engine, the ECT sensor temperature should rise steadily, then stabilise after the thermostat opens.

•	High resistance in the circuits of either the ECT or IAT sensor may set a DTC.

Reference Information

Schematic Reference

Engine Controls Schematics : LLW

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

Engine running for 1 min. Observe the DTC information with a scan tool. DTC P0115 should not set.
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

Ignition OFF, disconnect the harness connector at the B34 Engine Coolant Temperature Sensor.
Test for less than 5 Ω between the low reference circuit terminal 2 and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.

Ignition ON, verify the scan tool ECT sensor parameter is at -40°C (-40°F).

⇒	If greater than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module.

Caution: Do NOT use the low reference circuit in the component harness connector for this test. Damage to the control module may occur due to excessive current draw.

Note: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage and the sensor may be damaged.

Ignition ON, connect a 3 A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool ECT sensor parameter is greater than 142°C (288°F).

⇒	If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.

If all circuits test normal, test or replace the B34 Engine Coolant Temperature Sensor.

Component Testing

Dynamic Test

Test and record the resistance between the signal circuit terminal 2 and the low reference circuit terminal 1 at various ambient temperatures. Compare those measurements to the Temperature Versus Resistance table and verify that the resistance is within 5% of the specification.

⇒	If not within the specified range, replace the B34 Engine Coolant Temperature Sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Engine Coolant Temperature Sensor Replacement

•	Control Module References for engine control module replacement, setup, and programming