P0117 OBD-II Trouble Code: Engine Coolant Temperature (ECT) Sensor Circuit Low Output Problem

P0117 code definition

Engine Coolant Temperature (ECT) sensor circuit low output problem

What the P0117 code means

P0117 is the OBD-II generic code that indicates the engine control module (ECM) has seen the ECT sensor output go less than 0.14 Volts or more than 140°C (284°F).

What causes the P0117 code?

• ECT sensor input to the ECM went to more than 0.14 Volts or 140°C (284°F) indicating a short circuit in sensor or wiring.

• The ECT sensor or wiring is shorted.

What are the symptoms of the P0117 code?

• ECM turns on the Check Engine Light and goes into failsafe mode substituting input to 176° F.
• The engine may have a hard start when engine is cold.
• The engine may run rough and hesitate until the engine warms up.
• The engine should run close to normal once the engine warms up.

Note: The symptoms are determined by the manufacturer failsafe ECM strategy for the vehicle during a failure and may vary between manufacturers and vehicles.

How does a mechanic diagnose the P0117 code?

• A visual inspection to check for any electrical connector, wiring or sensor issues.

• The technician will scan and document the codes received and view the freeze frame data to see when the code was set.

• The codes should then be reset to clear the OBD-II fault codes and retest the vehicle to see if the code comes back.

• Disconnect ECT sensor, observe live data to see if readings go from over 284°F to -40°F.

• If readings go to -40° F then replace the ECT sensor if not then look for shorted harness, connector or ECM.

Common mistakes when diagnosing the P0117 code?

Not following these simple steps:

• Always do a visual inspection first.

• The manufacturer pinpoint test procedure follow step-by-step not skipping any steps.

• Do not replace an ECT sensor unless tests indicate a problem.

• Before installation of the new ECT sensor, try connecting it and viewing the ECM data to see if the temperature output from the sensor is as expected.

How serious is the P0117 code?

• The P0117 code will put the engine ECM to go into a failsafe mode.

• The failsafe mode may cause engine to run rough and hesitate until the engine warms up to operating temperature.

• Electrical cooling fans may run continuously.

What repairs can fix the P0117 code?

• Resetting the fault codes and perform a road test
• Repairing or replacing the ECT connector
• Repairing or replacing the wiring as necessary
• Replacing the ECT with a new sensor

Additional comments for consideration regarding the P0117 code

• The ECT sensor shorted is the most common failure.

• Some failures for code P0117 other than the sensor include a harness shorting or a connector corrosion issue.

Need help with a P0117 code?

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