GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2005 🢒 Bonneville 🢒 DTC 🢒 DTC P1115

Circuit Description

The engine coolant temperature (ECT) sensor is a variable resistor, sometimes called a thermistor, that measures the temperature of the engine coolant. The powertrain control module (PCM) supplies 5 volts to the ECT signal circuit. When the ECT is cold, the sensor resistance is high. When the ECT increases, the sensor resistance decreases. With high sensor resistance, the PCM detects a high voltage on the ECT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the ECT signal circuit. If the PCM detects an excessively high signal voltage, which is a low temperature indication, DTC P1115 sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

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

Conditions for Running the DTC

The engine run time is more than 1 minute.

Conditions for Setting the DTC
    • The ECT is less than -39°C (-38°F) for more than 10 seconds.
    • DTC 1115 runs continuously once the above condition is met.

Action Taken When the DTC Sets
    • The control module stores the DTC information into memory when the diagnostic runs and fails.
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
    • The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC
    • A current DTC Last Test Failed clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
    • Clear the DTC with a scan tool.

Step

Action

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

Observe the DTC information with a scan tool.

Is DTC P0118 set?

Go to DTC P0118

Go to Step 3

3
  1. Turn OFF the engine.
  2. Turn ON the ignition, with the engine OFF.
  3. Observe the engine coolant temperature (ECT) sensor parameter with a scan tool while moving the ECT sensor connector and the powertrain control module (PCM) connector. Refer to Inducing Intermittent Fault Conditions in Wiring Systems.

Does the scan tool indicate an abrupt change in value?

Go to Step 5

Go to Step 4

4

Observe the ECT parameter with a scan tool while moving the wiring harness at the ECT sensor and the PCM. Refer to Inducing Intermittent Fault Conditions in Wiring Systems.

Does the scan tool indicate an abrupt change in value?

Go to Step 6

Go to Step 7

5

Repair the connector and/or terminal as necessary. Refer to Connector Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 7

--

6

Repair the harness and/or wiring as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 7

--

7
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 60 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 8

8

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

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

System OK