Circuit Description
The engine coolant temperature (ECT) sensor is a thermistor mounted in the engine coolant stream. The powertrain control module (PCM) applies approximately 5.0 volts through a pull-up resistor to the engine coolant temperature (ECT) signal circuit. When the engine coolant is cold, the sensor, or thermistor resistance is high, and the PCM will measure a high signal voltage. As the engine coolant warms, the sensor resistance lessens, and the ECT signal voltage measured at the PCM drops. With a fully warmed-up engine, the ECT signal voltage should measure fro approximately 1.5 volts to 2.0 volts. When the PCM detects an excessively high signal voltage on the engine coolant temperature sensor signal circuit, DTC P0118 will set
Conditions for Running the DTC
The engine run time is longer than 15 seconds.
Conditions for Setting the DTC
| • | The ECT sensor signal indicates an engine coolant temperature that is less than -34°C (-30°F). |
| • | The above condition is 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/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:
Many situations may lead to an intermittent condition. Perform each inspection or test as directed.
Important: : Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.
| • | Loose terminal connection |
| - | Use a corresponding mating terminal to test for proper tension. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| - | Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| • | Damaged harness--Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
| • | Inspect the powertrain control module (PCM) and the engine grounds for clean and secure connections. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
If the condition is determined to be intermittent, reviewing the Snapshot or Freeze Frame/Failure Records may be useful in determining when the DTC or condition was identified.
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
This step verifies that the malfunction is present.
-
When the PCM is replaced, you must program the new PCM.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 |
Important: If DTC P1635 5 Volt Reference Circuit is also set, perform that diagnostic first. Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Is the ECT below the specified value? | -38°C or -36°F | |||
3 |
Does the scan tool indicate that DTC P0118 failed? | -- | Go to Diagnostic Aids | |
4 |
Important: If the 3-amp fuse blows, locate and repair the short to voltage on the sensor signal wire, and verify that the sensor was not damaged. Is ECT at the specified value? | 140°C or 284°F | ||
5 |
Important: If the 3-amp fuse blows, locate and repair the short to voltage on the sensor signal wire, and verify that the sensor was not damaged. Is ECT at the specified value? | 140°C or 284°F | ||
6 |
Did you find a problem? | -- | ||
7 |
Did you find a problem? | -- | ||
8 |
Did you find a problem? | -- | ||
9 |
Did you find a problem? | -- | ||
10 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Is action complete? | -- | -- | |
|
Important: You must program the replacement PCM. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | -- | ||
12 |
Does the scan tool indicate that DTC P0118 failed? | -- | System OK |
