AutoCodes – Mercedes-Benz – P0109 Mercedes-Benz

P0109 Mercedes-Benz Code - Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent

Quick Answer

The Manifold Absolute Pressure (MAP) sensor measures the pressure inside the intake manifold. Common causes include Faulty Manifold Absolute Pressure (MAP) Sensor, Manifold Absolute Pressure Sensor harness is open or shorted, Manifold Absolute 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: P0109 Mercedes-Benz indicates Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent.
Common causes: Common causes include Faulty Manifold Absolute Pressure (MAP) Sensor, Manifold Absolute Pressure Sensor harness is open or shorted, Manifold Absolute 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 7,958

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 May 20, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0109 Mercedes-Benz Description

The Manifold Absolute Pressure (MAP) sensor measures the pressure inside the intake manifold. Pressure in the intake manifold is affected by engine speed, throttle opening, air temperature, Barometric Pressure (BARO) and if equipped, turbocharger output. A diaphragm within the MAP sensor is displaced by the pressure changes that occur from the varying load and operating conditions of the engine. The sensor translates this action into electrical resistance.
The MAP sensor wiring includes 3 circuits. The Engine Control Module (ECM) supplies a regulated 5 volts to the sensor on a 5 V reference circuit. The ECM supplies ground on a low reference circuit. The MAP sensor provides a signal voltage to the ECM, relative to the pressure changes, on the MAP sensor signal circuit. The ECM converts the signal voltage input to a pressure value.
Under normal operation the greatest pressure that can exist in the intake manifold is at ignition ON, engine OFF, which is equal to the BARO. The lowest manifold pressure occurs when the vehicle is idling or decelerating. The ECM monitors the MAP sensor signal for pressure outside of the normal range.
The Diagnostic Trouble Code (DTC) will be set when the ECM detects that the MAP Sensor voltage is failing intermittently.

OBDII Code P0109 Mercedes-Benz - Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent - AutoCodes.com — P0109 Mercedes-Benz Code - Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent

What does this mean?

What are the Possible Causes of the DTC P0109 Mercedes-Benz?

Faulty Manifold Absolute Pressure (MAP) Sensor
Manifold Absolute Pressure Sensor harness is open or shorted
Manifold Absolute Pressure Sensor circuit poor electrical connection
Faulty Engine Control Module (ECM)

How to Fix the DTC P0109 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 P0109 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 P0109 Mercedes-Benz code?

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Need Help with the Code?

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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 P0109 Mercedes-Benz Code

1. What are the common symptoms of OBDII code P0109 in a Mercedes-Benz?

- Common symptoms include rough idling, poor acceleration, decreased fuel efficiency, and potential stalling of the engine.

2. What are the possible causes of the Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent code in a Mercedes-Benz?

- The code P0109 can be triggered by issues such as a faulty MAP sensor, damaged wiring or connectors, vacuum leaks, or a failed PCM (powertrain control module).

3. How can I diagnose the cause of OBDII code P0109 in my Mercedes-Benz?

- To diagnose the issue, you can perform a visual inspection of the MAP sensor and its wiring, use a multimeter to check for continuity, test the sensor's voltage output, and inspect for any vacuum leaks.

4. Can I continue driving my Mercedes-Benz with the P0109 code present?

- It is not recommended to drive your vehicle with the P0109 code as it can lead to further engine damage and potential safety hazards. It's best to address the issue promptly.

5. How can I repair the Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent code in my Mercedes-Benz?

- Repair options include replacing the faulty MAP sensor, repairing damaged wiring or connectors, fixing any vacuum leaks, and resetting the fault codes with an OBDII scanner.

6. Will resetting the fault codes with an OBDII scanner fix the P0109 code in my Mercedes-Benz?

- Resetting the fault codes may temporarily clear the code, but if the underlying issue causing the P0109 persists, the code is likely to reappear. It's important to address the root cause of the problem.

7. Can a DIY enthusiast fix the P0109 code in a Mercedes-Benz?

- Depending on your skill level and access to tools, some DIY enthusiasts may be able to address the P0109 code by replacing the MAP sensor or repairing wiring issues. However, if unsure, it's best to seek professional help.

8. How much does it typically cost to repair the Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent code in a Mercedes-Benz?

- The cost of repair can vary depending on the specific cause of the code and whether you choose to DIY or seek professional help. Costs may range from around $100 to $300 or more.

9. Are there any preventive measures I can take to avoid the P0109 code in my Mercedes-Benz?

- Regular maintenance, such as checking and replacing air filters, inspecting vacuum lines, and monitoring the condition of the MAP sensor, can help prevent issues that may trigger the P0109 code.

10. How long does it take to repair the P0109 code in a Mercedes-Benz?

- The repair time can vary based on the cause of the code and your experience level. Simple fixes like replacing the MAP sensor can be done in under an hour, while more complex issues may require several hours or a day.