P0117

Diagnostic Chart:

Description:

Wiring Diagram:

Circuit Description

The Engine Coolant Temperature (ECT) sensor is a thermistor (a variable resistor that changes along with engine coolant temperature) in series with a fixed resistor in the Powertrain Control Module (PCM). The PCM applies 5 volts to the ECT sensor. The PCM monitors the voltage across the ECT sensor and converts it into a temperature reading. When the engine is cold the ECT sensor resistance is high, and when the engine is warm the ECT sensor resistance is low. Therefore, when the engine is cold the PCM will receive a high voltage input, and when the engine is warm the PCM will receive a low voltage input.

Conditions for Setting the DTC

^ ECT sensor signal indicates an engine coolant temperature greater than 119°C (246°F).

^ Above condition is met for at least 0.5 seconds.

Action Taken When the DTC Sets

^ The Malfunction Indicator Lamp (MIL) will illuminate.

^ The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer.

^ The PCM will enter the Fail-Safe Function and assume the engine coolant temperature is 80°C (176°F) while stopping EGR, Idle Speed Control (ISC), A/C control and turning On the cooling fan.

Conditions for Clearing the MIL/DTC

^ The MIL will turn OFF after three consecutively passing cycles without a fault present.

^ A History DTC will clear after 40 consecutive warm-up cycles without a fault.

^ DTCs can be cleared by using a scan tool or by disconnecting the PCM battery feed.

Diagnostic Aids

Check for any of the following conditions:

^ When replacing the Intake Air Temperature (IAT) sensor the Temperature to Resistance Value scale may be used to test the sensor at various temperature levels to evaluate the possibility of a shifted (incorrectly calibrated) sensor. A shifted sensor could result in poor driveability complaints. Refer to IAT sensor / Description and Operation for additional IAT sensor specifications.

^ After the engine is started, the ECT sensor should rise steadily to about 95°C (203°F) and stabilize when the thermostat opens.

^ Verify that the engine is not overheating and has not been subjected to conditions which could create an overheating conditions (i.e., overload, trailer towing, hilly terrain, heavy stop and go traffic, etc.).

^ The engine cooling fan will turn ON when the DTC sets.

^ A poor connection at PCM. Inspect the wiring harness connectors for backed out terminal, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

^ A damaged wiring 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 fault.

If a DTC P0117 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

If any wiring repairs need to be made, Refer to Repair Procedures in Electrical Diagrams.

Test Description

The numbers below refer to the step numbers in the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. Determines if fault is present.

3. Review Freeze Frame data to determine when the DTC set. Always record this information.

4. This step determines if the fault is caused by a shorted signal return circuit or by a malfunctioning ECT sensor.