P1115

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




Circuit Description
The engine coolant temperature (ECT) sensor is a thermistor mounted in the engine coolant stream. The powertrain control module (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, Diagnostic Trouble Code P1115 will set. Diagnostic Trouble Code P1115 is a type D code.

Conditions for Setting the DTC
- Engine run time longer than 180 seconds.
- The ECT sensor signal is intermittently greater than -39 °C (-38 °F) (4.94 volts) for a total of 10 seconds over a 100-second period.

Action Taken When the DTC Sets
- The PCM will not illuminate the malfunction indicator lamp (MIL).
- The PCM will store conditions which were present when the Diagnostic Trouble Code set as Failure Records data only. This information will not be stored as Freeze Frame data.

Conditions for Clearing the DTC
- A history Diagnostic Trouble Code P1115 will clear after 40 consecutive warm-up cycles have occurred without a fault.
- Diagnostic Trouble Code P1115 can be cleared by using the Scan Tool's "Clear Info" function.

Diagnostic Aids
Check for the following conditions:
- Poor connection at PCM - Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection.
- Damaged harness - Inspect the wiring harness for damage: shorts to ground, shorts to battery positive, and open circuits. If the harness appears to be OK, observe the ECT display on the Tech 2 while moving connectors and wiring harnesses related to the ECT sensor. A change in the ECT display will indicate the location of the fault.

Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the Diagnostic Trouble Code to be set occurs. This may assist in diagnosing the condition.

Temperature Vs. Resistance Values:

Engine Coolant Temperature Sensor