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 (thermistor) resistance is high, and the PCM measures 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 P0118 is set when the PCM detects an excessively high signal voltage on the engine coolant temperature sensor signal circuit.
Conditions for Running the DTC
An engine run time longer than 3 seconds
Conditions for Setting the DTC
| • | The ECT sensor signal indicates an engine coolant temperature less than -13°C (9°F). |
| • | The above condition is present for at least 10 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has run and failed. |
| • | The PCM stores the conditions which were present when the DTC set as Freeze Frame and Fail Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns the MIL off during the third consecutive trip in which the diagnostic has run and passed. |
| • | The history DTC clears after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC may be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed. |
Diagnostic Aids
Inspect for the following conditions:
| • | A faulty connection at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. |
| • | 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 malfunction. |
| • | A skewed or mis-scaled ECT sensor. Refer to Temperature vs Resistance . |
If DTC P0118 cannot be duplicated, the information included in the Fail Records data may be useful in determining vehicle mileage since the DTC was last set. If the DTC occurs intermittently, performing the DTC P1115 Diagnostic Chart may isolate the cause of the malfunction.
Test Description
The number(s) below refer to the step number(s) on the Diagnostic Table:
-
Verifies that the malfunction is present.
-
If DTC P0118 can be repeated only by duplicating the Fail Records conditions, refer to the Temperature vs Resistance
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This vehicle is equipped with a powertrain control module (PCM) which utilizes an electrically erasable programmable read-only memory (EEPROM). When the PCM is replaced, the new PCM must be programmed.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Is the ECT less than the specified value? | -38°C (-36°F) | |||
Does the scan tool indicate DTC P0118 failed? | -- | Go to Diagnostic Aids | ||
4 |
Was a problem found? | -- | ||
5 |
Is the ECT equal to the specified value? | 140°C (284°F) | ||
6 |
Is the ECT at the specified value? | 140°C (284°F) | ||
7 |
Was a problem found? | -- | ||
8 |
Was a problem found? | -- | ||
9 |
Was a problem found? | -- | ||
10 |
Was a problem found? | -- | ||
11 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement Did you complete the repair? | -- | -- | |
|
Important: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming Replace the PCM. Did you complete the repair? | -- | -- | ||
13 |
Does the scan tool indicate DTC P0118 failed? | -- | System OK |
