AutoCodes – Mercedes-Benz – P2039 Mercedes-Benz

P2039 Mercedes-Benz Code - Reductant Injection Air Pressure Sensor 'A' Circuit Low

Quick Answer

The reductant system uses a selective reduction catalyst to improve exhaust emissions and fuel efficiency by injecting a reductant into the exhaust system. Common causes include Faulty Reductant Injection Air Pressure Sensor, Reductant Injection Air Pressure Sensor harness is open or shorted, Reductant Injection Air Pressure Sensor circuit poor electrical connection. 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: P2039 Mercedes-Benz indicates Reductant Injection Air Pressure Sensor 'A' Circuit Low.
Common causes: Common causes include Faulty Reductant Injection Air Pressure Sensor, Reductant Injection Air Pressure Sensor harness is open or shorted, Reductant Injection Air Pressure Sensor circuit poor electrical connection.
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 11,007

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Aug 04, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P2039 Mercedes-Benz Description

The reductant system uses a selective reduction catalyst to improve exhaust emissions and fuel efficiency by injecting a reductant into the exhaust system. The reductant also referred to as diesel exhaust fluid is a 32.5% solution of urea in deionized water. The reductant system reduces Nitrogen Oxides (NOx) present in the exhaust stream to nitrogen and water.
The Reductant Injection Air Pressure Sensor sends voltage reading information to the Powertrain Control Module (PCM). The PCM interprets these readings as pressure or exhaust gas temperature. The code is set when the voltage sent from the sensor to the PCM is out of factory specifications.

OBDII Code P2039 Mercedes-Benz - Reductant Injection Air Pressure Sensor 'A' Circuit Low - AutoCodes.com — P2039 Mercedes-Benz Code - Reductant Injection Air Pressure Sensor 'A' Circuit Low

What does this mean?

What are the Possible Causes of the DTC P2039 Mercedes-Benz?

Faulty Reductant Injection Air Pressure Sensor
Reductant Injection Air Pressure Sensor harness is open or shorted
Reductant Injection Air Pressure Sensor circuit poor electrical connection
Faulty Reductant Pump Assembly

How to Fix the DTC P2039 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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P2039 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 P2039 Mercedes-Benz code?

Need more information on how to fix the P2039 Mercedes-Benz code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P2039 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 P2039 Mercedes-Benz Code

1. What does the OBDII code P2039 mean for a Mercedes-Benz?

P2039 indicates a problem with the Reductant Injection Air Pressure Sensor 'A' Circuit, meaning the sensor is reporting a low voltage or pressure reading.

2. What are the common symptoms of the P2039 code in a Mercedes-Benz?

Symptoms may include the check engine light turning on, reduced engine performance, poor fuel efficiency, or issues with the diesel exhaust fluid (DEF) system.

3. What causes the P2039 code to appear in a Mercedes-Benz?

Common causes include a faulty reductant air pressure sensor, damaged or corroded wiring, a defective DEF injector, or issues with the control module.

4. Can I drive my Mercedes-Benz with the P2039 code?

It is not recommended to drive for long periods with this code, as it can lead to increased emissions and possible damage to the DEF system.

5. How can I diagnose the P2039 code on my Mercedes-Benz?

Diagnose the issue using an OBDII scanner to confirm the code, then inspect the reductant air pressure sensor, wiring, and connectors for damage or corrosion.

6. How do I fix the P2039 code on a Mercedes-Benz?

Repairs may involve replacing the reductant air pressure sensor, repairing damaged wiring, cleaning electrical connections, or reprogramming the control module if necessary.

7. How much does it cost to repair the P2039 code on a Mercedes-Benz?

Repair costs can vary, but replacing the reductant air pressure sensor typically costs between $100 and $300, excluding labor.

8. Can a dirty or clogged DEF injector cause the P2039 code?

Yes, a clogged or malfunctioning DEF injector can disrupt air pressure readings and trigger the P2039 code.

9. Will resetting the check engine light fix the P2039 code?

Resetting the light may temporarily clear the code, but the underlying issue must be addressed to prevent the code from returning.

10. Is the P2039 code related to emissions compliance in a Mercedes-Benz?

Yes, the P2039 code impacts the DEF system, which is critical for reducing nitrogen oxide emissions and maintaining compliance with emissions regulations.