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For 1990-2009 cars only

Circuit Description

The DTC P0115 Engine Coolant Temperature (ECT) Sensor Circuit diagnostic detects an out of range sensor signal. The ECT sensor is a thermistor. A thermistor is a resistor whose value varies with the temperature. The electrical resistance of the ECT sensor is high when the coolant temperature is cold, and the resistance is low when the coolant temperature is warm. The ECT sensor is wired in series with a fixed resistor in the powertrain control module (PCM). The PCM applies 5 volts to the ECT sensor. The PCM monitors the voltage across the ECT sensor and converts the voltage into a temperature reading. The voltage measured by the PCM will be high when the coolant temperature is cold, and low when the coolant temperature is warm.

Temperature

ECT Resistance

ECT Signal Voltage

Cold

High

High

Warm

Low

Low

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0115 Engine Coolant Temperature (ECT) Sensor Circuit

Conditions for Running the DTC

    • The ignition is ON.
    • DTC P0115 runs continuously once the above condition has been met.

Conditions for Setting the DTC

    • The temperature input is -40°C (-40°F), 4.91 volts, for at least 0.5 seconds.
        OR
    • The temperature input is 140°C (284°F), 0.14 volts, for at least 0.5 seconds.

Action Taken When the DTC Sets

    • The PCM illuminates the malfunction indicator lamp (MIL).
    • The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.
    • The PCM enters the Fail Safe Function in which the coolant temperature will default to 80°C (176°F).

Conditions for Clearing the MIL/DTC

    • The MIL turns OFF after 3 consecutively passing trips without a fault present.
    • A History DTC clears after 40 consecutive warm-up cycles without a fault.
    • Use the scan tool Clear DTC Information function.

Diagnostic Aids

    • If DTCs P0105, P0110, P0115, and P0120 are also set, the malfunction may be a faulty sensor ground circuit.
    • Check for a faulty electrical connection to the PCM.
    • Check for the proper operation of the engine cooling system and verify the correct coolant level.
    • Use the Temperature vs Resistance table in order to evaluate the possibility of a shifted ECT sensor. A shifted sensor could result in a DTC P0115. Refer to Temperature Versus Resistance .

An intermittent malfunction may be caused by a fault in the ECT sensor electrical circuit. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions .

Repair any electrical circuit faults that were found. Refer to Wiring Repairs in Wiring Systems.

If a DTC P0115 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. The Diagnostic System Check - Vehicle prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool, if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

  2. This step checks for a high input condition. If the scan tool reads 140°C (284°F), the input circuit may be the result of a short circuit.

  3. This step checks for a low input condition. If the scan tool reads -40°C (-40°F), the input circuit may be the result of an open circuit.

  4. This step determines if DTC P0115 is the result of a hard failure or an intermittent condition.

Step

Action

Values

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

Select the ECT sensor parameter on the scan tool.

Is the engine coolant temperature (ECT) sensor value greater than or equal to the specified value?

140°C (284°F)

Go to Step 5

Go to Step 3

3

Select the ECT sensor parameter on the scan tool.

Is the ECT sensor value less than or equal to the specified value?

-40°C (-40°F)

Go to Step 7

Go to Step 4

4

  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 2

Go to Diagnostic Aids

5

  1. Turn ON the ignition, with the engine OFF.
  2. Disconnect the ECT sensor electrical connector.
  3. Select the ECT sensor parameter on the scan tool.

Is the ECT sensor value equal to the specified value?

-40°C (-40°F)

Go to Step 13

Go to Step 6

6

  1. Turn OFF the ignition.
  2. Disconnect the powertrain control module (PCM) electrical connector at the PCM.
  3. Check the ECT sensor input circuit for a short to ground. Ensure that the input circuit is not shorted to the sensor ground circuit.
  4. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 15

Go to Step 14

7

  1. Disconnect the ECT sensor electrical connector.
  2. Jump the ECT input circuit and the sensor ground circuit together at the ECT sensor harness connector.
  3. Select the ECT sensor parameter on the scan tool.

Is the ECT sensor value more than or equal to the specified value?

140°C (284°F)

Go to Step 9

Go to Step 8

8

  1. Jump the ECT input circuit at the ECT sensor harness connector to chassis ground.
  2. Select the ECT sensor parameter on the scan tool.

Is the ECT sensor value more than or equal to the specified value?

140°C (284°F)

Go to Step 10

Go to Step 11

9

  1. Check for faulty electrical connections at the ECT sensor.
  2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 15

Go to Step 13

10

  1. Turn OFF the ignition.
  2. Disconnect the PCM connector at the PCM.
  3. Check the ECT sensor ground circuit for an open.
  4. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 15

Go to Step 12

11

  1. Turn OFF the ignition.
  2. Disconnect the PCM connector at the PCM.
  3. Check the ECT sensor input circuit for an open.
  4. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 15

Go to Step 12

12

  1. Check for a faulty ECT circuit terminal connection at the PCM.
  2. Repair as necessary.

Was a repair necessary?

--

Go to Step 15

Go to Step 14

13

Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement .

Is the action complete?

--

Go to Step 15

--

14

Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Is the action complete?

--

Go to Step 15

--

15

  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 16

Go to Step 2

16

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

System OK