AutoCodes – Mercedes-Benz – P0115 Mercedes-Benz

P0115 Mercedes-Benz Code - Engine Coolant Temperature Sensor 1 Circuit

Quick Answer

This fault code is stored in the Engine Control Module (ECM) when the output from the engine coolant temperature sensor is not as expected or missing. Common causes include Low engine coolant level, Faulty Engine Coolant Temperature (ECT) sensor, Faulty engine coolant thermostat. 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: P0115 Mercedes-Benz indicates Engine Coolant Temperature Sensor 1 Circuit.
Common causes: Common causes include Low engine coolant level, Faulty Engine Coolant Temperature (ECT) sensor, Faulty engine coolant thermostat.
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.

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Code Popularity 32,056

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Sep 11, 2019

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0115 Mercedes-Benz Description

This fault code is stored in the Engine Control Module (ECM) when the output from the engine coolant temperature sensor is not as expected or missing. The engine control module uses information from the intake air temperature sensor and engine oil temperature sensor to carry out a plausibility check on the signal. Engine coolant temperature sensors are normally a negative temperature coefficient thermistor. The signal voltage drops as the engine coolant temperature increases. The signal from the sensor is used to adjust the ignition system rate of advance and fuel injection system duration for various operating conditions. A faulty engine coolant temperature sensor may result in an engine over fuelling or not entering closed loop control. The rate of ignition advance is reduced when the engine is hot to reduce the possibility of engine knock occurring.

OBDII Code P0115 Mercedes-Benz - Engine Coolant Temperature Sensor 1 Circuit - AutoCodes.com — P0115 Mercedes-Benz Code - Engine Coolant Temperature Sensor 1 Circuit

What does this mean?

What are the Possible Causes of the DTC P0115 Mercedes-Benz?

Low engine coolant level
Faulty Engine Coolant Temperature (ECT) sensor
Faulty engine coolant thermostat
Engine Coolant Temperature (ECT) sensor harness is open or shorted
Engine Coolant Temperature (ECT) sensor circuit poor electrical connection
Faulty Engine Control Module (ECM)

How to Fix the DTC P0115 Mercedes-Benz?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

Mercedes Benz Code = 0405 (Heating system shutoff valve) has a short circuit to positive. (P0115)
Mercedes Benz Code = 0406 (Heating system shutoff valve) has a short circuit to ground. (P0115)
Mercedes Benz Code = 0407 (Heating system shutoff valve) has an open circuit in the wiring. (P0115)

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0115 Mercedes-Benz code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P0115 Mercedes-Benz code?

Need more information on how to fix the P0115 Mercedes-Benz code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0115 Mercedes-Benz code diagnosed by a professional: Find a repair shop in your area

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 P0115 Mercedes-Benz Code

1. What are common symptoms of OBDII code P0115 in a Mercedes-Benz related to the Engine Coolant Temperature Sensor 1 Circuit?

Common symptoms include issues with the engine starting, poor fuel economy, overheating, and the Check Engine light being illuminated.

2. What are some possible causes of OBDII code P0115 in a Mercedes-Benz?

Possible causes include a faulty engine coolant temperature sensor, damaged wiring or connectors, low coolant levels, or a malfunctioning engine control module.

3. How can I diagnose the cause of OBDII code P0115 in my Mercedes-Benz?

You can diagnose the issue by checking the engine coolant temperature sensor with a multimeter, inspecting the wiring and connectors for damage, ensuring proper coolant levels, and using an OBDII scanner to reset the code and monitor sensor readings.

4. Can I drive my Mercedes-Benz with OBDII code P0115 present?

It is not recommended to drive your vehicle with this code present, as it can lead to engine overheating, poor performance, and potential damage to engine components.

5. How can I repair OBDII code P0115 in my Mercedes-Benz?

Repair options include replacing the engine coolant temperature sensor, repairing any damaged wiring or connectors, refilling coolant levels, and clearing the code with an OBDII scanner.

6. Will OBDII code P0115 cause my Mercedes-Benz to fail an emissions test?

Yes, this code can cause your vehicle to fail an emissions test due to its impact on engine performance and emissions control systems.

7. Can a DIY enthusiast fix OBDII code P0115 in a Mercedes-Benz?

Depending on your skill level and access to tools, a DIY enthusiast may be able to fix this issue by following repair guides and utilizing basic automotive repair knowledge.

8. How much does it typically cost to repair OBDII code P0115 in a Mercedes-Benz?

The cost of repair can vary depending on the exact cause of the code, but it may range from $100 to $300 for parts and labor.

9. Are there any preventive measures to avoid OBDII code P0115 in a Mercedes-Benz?

Regular maintenance, such as checking coolant levels, inspecting sensors, and addressing any engine performance issues promptly, can help prevent this code from occurring.

10. How long does it take to repair OBDII code P0115 in a Mercedes-Benz?

The repair time can vary depending on the specific cause of the code and the complexity of the repair, but it may take anywhere from 1 to 3 hours to address this issue.