AutoCodes – Mercedes-Benz – P0140 Mercedes-Benz

P0140 Mercedes-Benz Code - O2 Sensor Circuit No Activity Detected Bank 1 Sensor 2

Quick Answer

The heated oxygen sensor 2 (HO2S), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. Common causes include Faulty Rear Heated Oxygen Sensor Bank 1, Rear Heated Oxygen Sensor Bank 1 harness is open or shorted, Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection. Severity is Moderate - service should be scheduled soon. The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

What it means: P0140 Mercedes-Benz indicates O2 Sensor Circuit No Activity Detected Bank 1 Sensor 2.
Common causes: Common causes include Faulty Rear Heated Oxygen Sensor Bank 1, Rear Heated Oxygen Sensor Bank 1 harness is open or shorted, Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection.
Severity: Moderate - service should be scheduled soon.
Can I drive?: The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

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Code Popularity 24,243

How popular is this code, among other codes? Low

Repair Importance Level

Moderate (Service soon) (2 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Apr 12, 2019

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0140 Mercedes-Benz Description

The heated oxygen sensor 2 (HO2S), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near the ideal stoichiometric ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The Engine Control Module (ECM) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes Lean. The ECM interprets Lean when the HO2S voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The ECM interprets Rich when the HO2S voltage is above 0.45 V.

OBDII Code P0140 Mercedes-Benz - O2 Sensor Circuit No Activity Detected Bank 1 Sensor 2 - AutoCodes.com — P0140 Mercedes-Benz Code - O2 Sensor Circuit No Activity Detected Bank 1 Sensor 2

What does this mean?

What are the Possible Causes of the DTC P0140 Mercedes-Benz?

Faulty Rear Heated Oxygen Sensor Bank 1
Rear Heated Oxygen Sensor Bank 1 harness is open or shorted
Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection
Inappropriate fuel pressure
Faulty fuel injectors
Intake air leaks may be faulty
Exhaust gas leaks

How to Fix the DTC P0140 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

Replacing the Rear Heated Oxygen Sensor Bank 1 usually takes care of the problem.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0140 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 P0140 Mercedes-Benz code?

Need more information on how to fix the P0140 Mercedes-Benz code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0140 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 P0140 Mercedes-Benz Code

1. What does the OBDII code P0140 for a Mercedes-Benz mean?

The code P0140 indicates that the O2 sensor circuit for Bank 1 Sensor 2 is not detecting any activity.

2. What are common symptoms of the O2 Sensor Circuit No Activity Detected Bank 1 Sensor 2 code?

Common symptoms include poor fuel economy, rough idling, engine hesitation, and an illuminated check engine light.

3. What are possible causes of the P0140 code in a Mercedes-Benz?

Possible causes include a faulty O2 sensor, wiring issues, a blown fuse, exhaust leaks, or problems with the engine computer.

4. What should I do if my Mercedes-Benz shows the P0140 code?

If your Mercedes-Benz displays the P0140 code, it is recommended to have the O2 sensor tested and replaced if necessary. Checking the wiring and connections is also advised.

5. Can I continue driving my Mercedes-Benz with the P0140 code?

It is not recommended to drive your vehicle with the P0140 code as it can lead to decreased fuel efficiency and potential damage to the catalytic converter.

6. How can I prevent the P0140 code from appearing in my Mercedes-Benz?

Regular maintenance of your vehicle, including checking and replacing O2 sensors as needed, can help prevent the recurrence of the P0140 code.

7. Will resetting the check engine light fix the P0140 code in my Mercedes-Benz?

Resetting the check engine light may temporarily turn it off, but it will not fix the underlying issue causing the P0140 code.

8. How much does it cost to repair the O2 Sensor Circuit No Activity Detected Bank 1 Sensor 2 in a Mercedes-Benz?

The cost of repairing the P0140 code can vary depending on the cause of the issue, but it typically involves replacing the O2 sensor, which can range from $100 to $300.

9. Can I replace the O2 sensor in my Mercedes-Benz myself?

Replacing the O2 sensor can be a DIY project for some car owners with the necessary tools and knowledge. However, it is recommended to consult a professional mechanic for proper installation.

10. How long does it take to repair the O2 Sensor Circuit No Activity Detected Bank 1 Sensor 2 in a Mercedes-Benz?

The repair time for the P0140 code can vary depending on the exact cause of the issue, but it typically takes around 1-2 hours for a mechanic to diagnose and replace the faulty O2 sensor.