DTC P1115 Engine Coolant Temperature (ECT) Sensor Circuit Intermittent High Voltage. Buick GL7 (Export) 2000

For 1990-2009 cars

### 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 of about 5.0 volts through a pull-up resistor to the ECT signal circuit. When the engine coolant is cold, the sensor resistance is high and 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 decreases. 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, DTC P1115 will set.

### Conditions for Running the DTC

The engine is running for 15 seconds.

### Conditions for Setting the DTC

• | The ECT is intermittently less than -39°C (-37°F).

• | The above conditions are present for more than 3 seconds.

### Action Taken When the DTC Sets

The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.

### Conditions for Clearing the MIL/DTC

• | The DTC becomes history when the conditions for setting the DTC are no longer present.

• | The history DTC clears after 40 malfunction free warm-up cycles.

• | The PCM receives a clear code command from the scan tool.

### Diagnostic Aids

Inspect for the following conditions:

• | A poor connection at the PCM. Inspect the harness connectors for the following conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems:

- | Backed-out terminals

- | Improper mating

- | Broken locks

- | Improperly formed or damaged terminals

- | Poor terminal-to-wire connection

• | A damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the ECT display on the scan tool while moving the connectors and the wiring harnesses related to the ECT sensor. A change in the ECT display indicates the location of the fault. Refer to Wiring Repairs in Wiring Systems.

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

#### DTC P1115 - ECT Sensor Circuit Intermittent High Voltage

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | With a scan tool select Diagnostic Trouble Codes (DTCs). Does the scan tool indicate DTC P0118 also set? | -- | Go to DTC P0118 Engine Coolant Temperature (ECT) Sensor Circuit High Voltage | Go to Step 3
3 | Are DTCs P1106, P1111, or P1121 also set? | -- | Go to Step 8 | Go to Step 4
4 | Inspect for a faulty ground circuit connection at the ECT sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 5
5 | Inspect for a faulty signal circuit connection at the ECT sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 6
6 | Test the signal circuit of the ECT sensor for an intermittent open. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7
7 | Test the signal circuit of the ECT sensor for an intermittent short to voltage. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 8
8 | Inspect for a faulty sensor ground circuit connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9
9 | Test the ground circuit of the ECT sensor for an intermittent open or a faulty splice. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Diagnostic Aids

10

1. Use the scan tool in order to clear the DTCs.
2. Operate the vehicle within the Failure Records conditions as noted.

Does the DTC reset?

--

Go to Step 2

System OK