Circuit Description
The Engine Coolant Temperature (ECT) sensor is a thermistor that controls the signal voltage to the PCM. When the engine is cold, the sensor resistance is high, therefore the PCM will see a high signal voltage. As the engine warms, the sensor resistance becomes less and the voltage drops. The voltage measured across the thermister is interpreted as a temperature. This is a type B DTC.
Conditions for Setting the DTC
| • | The engine has been running for at least 8 minutes. |
| • | The ECT is less than -30°C (-22°F). |
| • | The conditions were met for 2 seconds. |
Action Taken When the DTC Sets
Idle increase.
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL off after three consecutive trips without a fault condition. |
| • | A History DTC will clear after forty consecutive warm-up cycles during which the diagnostic does not fail (the coolant temperature has risen 5°C (40°F) from start up coolant temperature and engine coolant temperature exceeds 71°C (160°F) that same ignition cycle). |
| • | Use of a Scan Tool will clear the DTC codes. |
Diagnostic Aids
Check the harness routing for a potential short to voltage. After the engine is started, the ECT temperature should rise steady to about 85°C (185°F). A mis-scaled sensor could result in poor driveability complaints.
Test Description
The number(s) below refer to step number(s) on the Diagnostic Table.
-
This test determines if P0118 is an intermittent condition.
-
This test will determine if signal circuit is open, or a malfunctioning PCM.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Important: Before clearing the DTC(s), use the scan tool Capture Info in order to record the Freeze Frame and failure records for reference, as the data will be lost when the Clear Info function is used. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
Does the ECT display a temperature colder than or equal to the specified value? | -30°C (-22°F) | |||
Does the scan tool display an ECT greater than or equal to the specified value? | 151°C (303°F) | |||
4 | Jumper the ECT sensor signal circuit to a known good ground. Does the scan tool display an ECT greater than the specified value? | 151°C (303°F) | ||
5 | The DTC is intermittent. If no other DTC(s) are stored, refer to Diagnostic Aids. Are there any other DTCs stored? | -- | Go to the Applicable DTC Table | Go to Diagnostic Aids |
6 | Inspect the sensor connector and the PCM connector for a proper connection. Was a problem found? | -- | ||
7 | Check the ECT sensor ground circuit for an open between the ECT sensor and the PCM. Was a problem found? | -- | ||
8 | Check the ECT sensor signal circuit for an open between the ECT sensor and the PCM. Was a problem found? | -- | ||
9 | Repair the circuit as necessary. Is the action complete? | -- | -- | |
10 | Replace the ECT sensor. Refer to Engine Coolant Temperature (ECT) Sensor Replacement . Is the action complete? | -- | -- | |
11 | Replace the PCM. Important: The new PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | |
12 |
Does the Scan Tool indicate that this diagnostic Passed? | -- | ||
13 | Use the Scan Tool in order to select Capture Info, Review Info. Are there any DTCs displayed that have not been diagnosed? | -- | Go to the Applicable DTC Table | System OK |
