Engine-CodesSubaru – P0118 Subaru

P0118 Subaru Code - Engine Coolant Temperature Circuit High Input

Quick Answer

The P0118 code for Subaru vehicles indicates an issue with the Engine Coolant Temperature (ECT) sensor circuit registering a high input. Common causes include Faulty ECT Sensor: A malfunctioning ECT sensor can send incorrect temperature readings to the ECM, triggering the P0118 code, Wiring Issues: Damaged or corroded wiring in the ECT sensor circuit can disrupt the signal and cause a high input reading, Connector Problems: Loose or damaged connectors in the ECT circuit can lead to poor electrical connections and trigger the code. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
P0118 Subaru indicates Engine Coolant Temperature Circuit High Input.
Common causes
Common causes include Faulty ECT Sensor: A malfunctioning ECT sensor can send incorrect temperature readings to the ECM, triggering the P0118 code, Wiring Issues: Damaged or corroded wiring in the ECT sensor circuit can disrupt the signal and cause a high input reading, Connector Problems: Loose or damaged connectors in the ECT circuit can lead to poor electrical connections and trigger the code.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
Table of contents Created and updated by William Orellana on Sep 12, 2024
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Code P0118 Subaru Description

The P0118 code for Subaru vehicles indicates an issue with the Engine Coolant Temperature (ECT) sensor circuit registering a high input. The ECT sensor is responsible for monitoring the temperature of the engine coolant and sending this information to the engine control module (ECM). When the ECM detects a high input signal from the ECT sensor, it may trigger the P0118 code, indicating a potential problem with the coolant temperature reading.

OBDII Code P0118 Subaru - Engine Coolant Temperature Circuit High Input
P0118 Subaru Code - Engine Coolant Temperature Circuit High Input

Common Causes of P0118 Subaru

  1. Faulty ECT Sensor: A malfunctioning ECT sensor can send incorrect temperature readings to the ECM, triggering the P0118 code.
  2. Wiring Issues: Damaged or corroded wiring in the ECT sensor circuit can disrupt the signal and cause a high input reading.
  3. Connector Problems: Loose or damaged connectors in the ECT circuit can lead to poor electrical connections and trigger the code.
  4. ECM Malfunction: A faulty ECM may misinterpret the coolant temperature data from the ECT sensor, resulting in the P0118 code.
  5. Coolant Contamination: Contaminated or degraded engine coolant can affect the ECT sensor's performance and trigger the high input signal.

Symptoms of P0118 Subaru

  1. Check Engine Light: The most common symptom associated with the P0118 code is the illumination of the check engine light on the vehicle's dashboard.
  2. Engine Overheating: A faulty ECT sensor may provide inaccurate temperature readings, leading to engine overheating.
  3. Poor Fuel Economy: Incorrect coolant temperature data can result in improper fuel delivery, causing decreased fuel efficiency.
  4. Rough Idling: The engine may experience rough idling or stalling due to incorrect coolant temperature readings.
  5. Reduced Performance: The vehicle may exhibit reduced performance or power output as a result of the P0118 code.

How to Fix P0118 Subaru

  1. Diagnose the Issue: Use a diagnostic scanner to retrieve the P0118 code and perform a thorough inspection of the ECT sensor, wiring, and connectors.
  2. Test ECT Sensor: Check the ECT sensor's resistance and compare it to specifications to determine if it is faulty and needs replacement.
  3. Inspect Wiring and Connectors: Examine the wiring harness and connectors for any damage, corrosion, or loose connections that may be causing the high input signal.
  4. Replace ECT Sensor: If the ECT sensor is determined to be faulty, replace it with a new sensor following manufacturer guidelines.
  5. Clear Codes and Test: After completing the repair, clear the P0118 code from the ECM's memory and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix P0118 Subaru

The typical repair costs for addressing a P0118 code on a Subaru vehicle can vary depending on the specific cause of the issue and the extent of the repairs needed. In general, replacing a faulty ECT sensor can cost between $50 and $150 for the part, with additional labor costs ranging from $80 to $150 per hour. The total repair cost may range from $150 to $300 or more, depending on the shop's labor rates and any additional components that require replacement. It's advisable to consult with a qualified mechanic or auto repair shop to obtain a more accurate estimate based on the vehicle's make and model, as well as the local labor rates in your area.

Tech Notes for P0118 Subaru









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When is the Code Detected?

An excessively high voltage from the sensor is sent to ECM.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0118 Subaru Code

What does the OBDII code P0118 mean for a Subaru?

P0118 indicates a high input voltage from the Engine Coolant Temperature (ECT) sensor circuit, suggesting an issue with the sensor or its wiring.

What are the common symptoms of code P0118 in a Subaru?

Symptoms include poor fuel economy, difficulty starting, engine overheating, rough idling, and the check engine light being illuminated.

What causes the P0118 code on a Subaru?

Causes can include a faulty ECT sensor, damaged wiring or connectors, a short circuit, or issues with the vehicle's ECU.

Can I drive my Subaru with a P0118 code?

Driving with a P0118 code is not recommended as it can lead to engine overheating, poor performance, or further damage to the engine.

How do I fix the P0118 code on my Subaru?

Repair steps include inspecting and replacing the ECT sensor, checking and repairing wiring or connectors, and ensuring the ECU is functioning properly.

Where is the Engine Coolant Temperature sensor located in a Subaru?

The ECT sensor is usually located near the thermostat housing or in the engine block, depending on the model.

Can a bad ECT sensor affect fuel economy in a Subaru?

Yes, a faulty ECT sensor can cause incorrect temperature readings, leading to improper air-fuel mixture and reduced fuel efficiency.

What tools are needed to diagnose the P0118 code in a Subaru?

You’ll need an OBDII scanner, a multimeter for testing voltage and resistance, and basic hand tools to access the sensor and wiring.

How much does it cost to repair a P0118 code on a Subaru?

Repair costs vary but typically range from $50 to $200 for parts and labor, depending on whether just the sensor or additional components need replacement.

Can a P0118 code be triggered by low coolant levels in a Subaru?

Low coolant levels are unlikely to directly trigger a P0118 code but can cause engine overheating, which might indirectly affect the ECT sensor’s readings.

Discuss the causes and fixes for P0118 Subaru OBDII Code

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