P1115 - FAULT CODE - OBD2

POST UPDATED IN February, 2023

P1115 Code failures by brands

P1115 ACURA, BUICK, CADILLAC, CHEVROLET, GMC, HONDA, PONTIAC, SATURN, SUZUKI: ENGINE COOLANT TEMPERATURE INTERMITTENT HIGH VOLTAGE.

Description of DTC code P1115

The ECT (Engine Coolant Temperature Sensor) can be described as a thermistor that is installed in the engine coolant flow. To this sensor, the ECM applies 5 volts for a reference circuit by using a pull-up resistor to the ECT signal circuit.

When the engine coolant is cold, the resistance of the Engine Coolant Temperature Sensor becomes high, controlling the ECM to a high signal voltage. As the coolant reaches higher temperatures, the sensor resistance decreases and the sensor signal voltage measured at the ECM drops.

With a fully warmed-up engine, the ECT sensor signal voltage should be approximately 1.5 to 2.0 volts. If the ECM detects that the signal is intermittently above the range set by the manufacturer, the P1115 OBDII fault code will be set.

How does the P1115 Fault Code work?

P1115 is a manufacturer-specific OBD-II code for a voltage problem with the engine coolant temperature or intake air temperature. It occurs with the signal delivered to the engine computer above the manufacturer’s setting. A high voltage reading is usually related to a drop in engine coolant or intake air temperature, which is read by gauges. This code is very similar to a P1114 except the voltage reading is high.

The cause of a P1115 code not solely depends on what the code prints but what your vehicle is doing, as they are manufacturer specific. Some codes could target a faulty engine temperature sensor specifically, requiring your mechanic to perform a visual scan and test the signal delivered by the sensor. With a P1115 code, your mechanic should look for a higher signal delivered by the sensors. If a sensor’s readings are not within the manufacturer’s settings, it surely will need to be changed.

Symptoms of fault code P1115

Some of the symptoms of faulty intake air temperature sensors range from lack of power, cold start problems, and poor fuel economy. A faulty coolant temperature sensor usually just results in a temperature reading above the actual temperature or an inoperable temperature gauge. Some of its prevalent symptoms are:

  • Check Engine light on.
  • A light illuminates on the dashboard warning of cooling system failure.
  • Engine temperatures are higher than usual.

Causes of OBD2 P1115

The factors that cause the storage of the P1115 OBD2 diagnostic code are as follows:

  • ECM connections may be faulty.
  • The ECT sensor circuit may have damage to the wiring or connectors.
  • The Engine Coolant Temperature Sensor could be faulty.

Since all P1XXX codes are manufacturer-specific, it is essential to have a professional-grade OBD-II scanner checking the code to ensure that the problem is corrected. This is particularly common with P1115 codes as each manufacturer will request varying repair techniques. For instance, Mazda-specific codes require troubleshooting the intake air temperature sensors while Honda processes the engine coolant temperature sensor.

Possible solutions of the DTC code P1115

Faulty intake air temperature tests can result in a wide range of unpleasant driving characteristics, so it is very important to correct a P1115 as quickly as possible. Codes related to an engine coolant temperature sensor can be even more important because they typically have higher coolant readings than what is actually flowing through the engine. Here are some of the steps to troubleshoot the DTC P1115 OBDII code:

  • Consult the Service Bulletins. The content of these will be useful when diagnosing a failure.
  • Perform an On-Board Diagnostics (EOBD) check to see if any other DTCs are set.
  • Inspect the condition of the connectors, wires, and other electrical components associated with the ECT Sensor. If any of these components are found to be damaged due to corrosion or wear, make repairs as appropriate.
  • Check the electrical connections of the ECM, in order to verify that they meet the requirements for good system performance.
  • Measure the ground signal and the ECT sensor signal voltage. If you discover a short or open circuit, make repairs.

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