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 P0117 is set when the PCM detects an excessively low signal voltage on the ECT 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 more than 134°C (274°F). |
| • | 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
Check for the following conditions:
| • | A faulty connection at PCM. Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connections. |
| • | 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 P0117 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 P1114 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:
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Verifies that the malfunction is present
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If DTC P0117 can be repeated only by duplicating the Fail Records conditions, refer to Temperature vs Resistance . The table may be used to test the engine coolant temperature (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.
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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 engine coolant temperature (ECT) more than the specified value? | 139°C (282°F) | |||
Does the scan tool indicate DTC P0117 Failed This Ign? | -- | Go to Diagnostic Aids | ||
4 |
Does the ECT equal the specified value? | -39°C (-38°F) | ||
5 |
Did you complete the repair? | -- | ||
6 | 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? | -- | -- | ||
8 |
Does the scan tool indicate DTC P0117 Failed This Ign? | -- | System OK |
