DTC P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low 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 decreases 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.

### Conditions for Running the DTC

The engine is running.

### Conditions for Setting the DTC

• | The ECT sensor indicates an engine coolant temperature of more than 140°C (283°F).

• | The above condition is present for more than 3 seconds.

### Action Taken When the DTC Sets

• | The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.

• | The PCM will store conditions which were present when the DTC set as Freeze Frame/Failure Records data.

### Conditions for Clearing the MIL/DTC

• | The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has run and passed.

• | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

• | The DTC can be cleared by using a scan tool.

### Diagnostic Aids

Inspect for the following conditions:

• | Poor connection at the PCM--Inspect harness connectors for:

- | Backed-out terminals

- | Improper mating

- | Broken locks

- | Improperly formed or damaged terminals

- | Poor terminal-to-wire connections

• | Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

• | 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 will indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems.

If DTC P0117 cannot be duplicated, the information included in the Failure Records data can be useful in determining the vehicle mileage since the DTC was last set. If it is determined that the DTC occurs intermittently, performing the DTC P1114 Engine Coolant Temperature (ECT) Sensor Circuit Intermittent Low Voltage may isolate the cause of the fault.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. Verifies that the fault is present.

2. If DTC P0117 can be repeated only by duplicating the Failure Records conditions, refer to the Temperature vs Resistance table. The table may be used to test the ECT sensor at various temperatures in order to evaluate the possibility of a shifted sensor that may be shorted above or below a certain temperature. If this is the case, replace the ECT sensor. If the ECT sensor appears to be OK, the fault is intermittent.

3. This vehicle is equipped with a PCM which utilizes an electrically erasable programmable read-only memory (EEPROM). If the PCM is replaced, the new PCM must be programmed.

#### DTC P0117 - ECT Sensor Circuit Low 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

1. Turn ON the ignition, leaving the engine OFF.
2. With a scan tool, observe the ECT parameter.

Is the ECT more than the specified value?

139°C (282°F)

Go to Step 4

Go to Step 3

3

1. With a scan tool, review and record the Failure Records data.
2. Operate the vehicle within the Failure Records conditions as noted.

Does scan tool indicate DTC P0117 failed this ignition?

--

Go to Step 4

Go to Diagnostic Aids

4

1. Turn OFF the ignition.
2. Disconnect the ECT sensor.
3. Turn ON the ignition, leaving the engine OFF.
4. With a scan tool, observe the ECT parameter.

Is the ECT less than the specified value?

-38°C (-36°F)

Go to Step 6

Go to Step 5

5 | Test the ECT sensor signal circuit for a short to ground or a short to the sensor ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 7
6 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 8 | --
7 | Important: : The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | Go to Step 8 | --

8

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