For 1990-2009 cars
Engine Controls Components
Engine Controls Schematics
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The engine coolant temperature (ECT) sensor is a thermistor mounted in the engine coolant stream. The 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. DTC P0117 will set when the PCM detects an excessively low signal voltage on the engine coolant temperature sensor signal circuit.

### Conditions for Running the DTC

Engine run time longer than 15 seconds.

### Conditions for Setting the DTC

• | The ECT sensor signal indicates an engine coolant temperature greater than 139°C (282°F).

• | Above condition present for at least 10 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 and Failure Records data.

### Conditions for Clearing the MIL/DTC

• | The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been 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 the scan tool.

### 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. If the harness appears to be OK, observe the ECT display on the scan tool while moving connectors and wiring harnesses related to the ECT sensor. A change in the ECT display will indicate the location of the malfunction.

• | Skewed or mis-scaled ECT Sensor.

| Refer to Temperature Versus Resistance table.

If DTC P0117 cannot be duplicated, the information included in the Fail Records data can be useful in determining vehicle mileage since the DTC was last set. If it is determined that the DTC occurs intermittently, performing the DTC P1114 Diagnostic Chart may isolate the cause of the malfunction.

### Test Description

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

1. Verifies that the malfunction is present

2. If DTC P0117 can be repeated only by duplicating the Fail Records conditions, refer to Temperature vs Resistance Table. The table may be used to test the ECT sensor at various temperatures 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 malfunction is intermittent; refer to Diagnostic Aids.

3. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed. Refer to PCM Replacement/Programming.

#### DTC P0117 - ECT Sensor Circuit Low Voltage

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Turn ON the ignition switch.
2. Observe the ECT display on the scan tool.

Is ECT display greater than the specified value?

139°C (282°F)

Go to Step 4

Go to Step 3

3 |

1. Verify that the ignition switch is ON.
2. Review and record scan tool Fail Records data.
3. Operate the vehicle within Fail Records conditions as noted.
4. Using a scan tool, monitor Specific DTC info for DTC P0117.

Does the scan tool indicate DTC P0117 failed this ignition?

--

Go to Step 4

Go to Diagnostic Aids

4 |

1. Disconnect the ECT sensor electrical connector.
2. Observe the ECT display on the scan tool.

Is ECT less than the specified value?

-39°C (-38°F)

Go to Step 6

Go to Step 5

5 |

1. Turn OFF the ignition switch.
2. Disconnect the PCM.
3. Check the ECT signal circuit for a short to ground or a short to the ECT sensor ground circuit.
4. If a problem is found, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

--

Go to Step 8

Go to Step 7

6 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Is action complete? | -- | Go to Step 8 | --
7 | Important: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is action complete? | -- | Go to Step 8 | --
8 |

1. Verify that the ignition is ON.
2. Clear DTCs.
3. Operate the vehicle within Fail Records conditions as noted.
4. Using a scan tool, monitor Specific DTC info for DTC P0117.

Does the scan tool indicate DTC P0117 failed this ignition?

--

Go to Step 2

System OK