P0115

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.

CONDITIONS FOR RUNNING THE DTC
The engine is running.

CONDITIONS FOR SETTING THE DTC
- The temperature input is -40°C (-40°F) for at least 0.5 seconds.

OR

- The temperature input is 140°C (284°F) 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 vs 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. Intermittent Conditions

Repair any electrical circuit faults that were found. Refer to refer to Diagnostic Aids for Circuit Testing and Wiring Repair Procedures.

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

Steps 1-5:

Steps 6-9:

Steps 10-14:

Steps 15-16:

The numbers below refer to the step numbers on the diagnostic table.
1. The Diagnostic System Check-Computers and Controls Systems 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.