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P0117 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

P0117 is a diagnostic trouble code that means “Engine Coolant Temperature Sensor 1 Circuit Low.” The low voltage input from the Engine Coolant Temperature (ECT) sensor 1 has been recognized by the vehicle’s Powertrain Control Module (PCM).

Meaning

The OBD-II trouble code P0117 indicates that the ECT sensor output is less than 0.14 Volts or above 140°C (284°F) and the Engine Control Module (ECM) has detected this.

The ECT sensor detects temperature fluctuations in your engine’s coolant. It sends the data to the PCM, which utilizes it to control the air-to-fuel ratio, cooling fan operation, ignition spark timing, and other powertrain-related outputs.

The OBD code P0117 is stored in your vehicle’s memory when the PCM detects a signal voltage that is lower than the sensor’s usual operating range. The PCM may detect a low signal from the ECT sensor, indicating that the engine coolant is too hot.

Causes

The P0117 code, like other OBD-II codes, has a variety of causes. To determine a good repair, it’s critical to pinpoint the actual cause of the problem. The most prevalent reason for this error code is shorted wiring. 

Other factors to consider are:

  • ECT sensor that has been damaged
  • Sensor wiring with a high resistance
  • Connectors that are damaged or malfunctioning
  • ECT or PCM wire harness damage or loose terminals
  • Engine is overheated
  • Flaw in a PCM

Symptoms

There are a few warning signals to check for if you receive the P0117 code. This code indicates that the ECT sensor is malfunctioning and that the engine coolant temperature is too high. The following is a list of the most prevalent symptoms associated with this error code:

  • The Check Engine Light illuminates, and the ECM enters failsafe mode, changing the input temperature to 176° F
  • When the engine is cold, it may be difficult to start
  • Until the engine warms up, it may run rough 
  • Once the engine has warmed up, it should run close to normal
  • Tailpipe emits a cloud of black smoke
  • Bad fuel economy 
  • Engine overheating may cause it to start and then breakdown

Diagnosis

For the correct diagnosis and solution of the error code P0117, you should follow the steps mentioned below:

  • A visual inspection is performed to look for any faults with electrical connectors, wiring, or sensors
  • The technician will scan and document the codes that have been received, as well as examine the freeze frame data to determine when the code was set
  • The codes should be reset to clear the OBD-II fault codes, and the vehicle should be retested to see whether the code reappears
  • Disconnect the ECT sensor and watch the live data to see if the temperature drops from above 284°F to -40°F
  • If the temperature readings drop below -40° F, replace the ECT sensor; otherwise, seek a shorted harness, connection, or ECM

Common mistakes

Failure to follow these simple steps:

  • Always start with a visual inspection
  • Follow the manufacturer’s test process step by step, without skipping any
  • Replace an ECT sensor only if tests reveal a problem
  • Try connecting the new ECT sensor and monitoring the ECM data to see if the sensor temperature output is as expected before installing

How serious is this?

  • The engine ECM will enter failsafe mode if the P0117 code is entered
  • Until the engine warms up to operating temperature, the failsafe mode may cause the engine to run rough 
  • Continuous operation of electrical cooling fans is possible.

What repairs can fix the code?

repair manuals

There are as many ways to correct this code as there are causes. Of course, this requires a full diagnosis to determine the specific cause of the problem. Some common solutions to this code are:

  • After resetting the fault codes, perform a test drive
  • Repair or replace ECT connection 
  • As needed, repair or replace the wiring
  • ECT replaced with a new sensor

Related codes

  • P0115 – Engine Coolant Temperature Sensor Circuit 1 Malfunction
  • P0116 – Engine Coolant Temperature Sensor Circuit 1 Range/Performance Problem
  • P0118 – Engine Coolant Temperature Sensor Circuit 1 High Input
  • P0119 – Engine Coolant Temperature Sensor Circuit 1 Intermittent
  • P0125 – Insufficient Coolant Temperature for Closed Loop Fuel Control. 
  • P0128 – Engine Coolant Temperature Below Thermostat Regulating Temperature

Conclusion

The majority of P0117 code symptoms point to engine performance difficulties. This implies that it must be resolved right away. P0117 can cause the vehicle to enter a failsafe mode, which restricts the vehicle’s speed and/or gear range. Deal with the problem at the earliest. As soon as the code appears or a combination of its symptoms appears, stop driving the car and take it to a professional mechanic. Ignoring this error code could result in the further engine and vehicle damage.

P0117 Code – What Does It Mean & How To Fix It

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