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P11BF Buick Code - O2 Reference Voltage Circuit Low Voltage (NOx Sensor 2)

Quick Answer

The Nitrogen Oxides (NOx) sensors are part of the selective catalytic reduction system, a device used to reduce NOx emission on diesel engines. Common causes include Faulty Nitrogen Oxides (NOx) Sensor 2, Nitrogen Oxides Sensor 2 harness is open or shorted, Nitrogen Oxides Sensor 2 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: P11BF Buick indicates O2 Reference Voltage Circuit Low Voltage (NOx Sensor 2).
Common causes: Common causes include Faulty Nitrogen Oxides (NOx) Sensor 2, Nitrogen Oxides Sensor 2 harness is open or shorted, Nitrogen Oxides Sensor 2 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 357

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

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Table of contents Created and updated by William Orellana on Mar 24, 2024

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P11BF Buick Description

The Nitrogen Oxides (NOx) sensors are part of the selective catalytic reduction system, a device used to reduce NOx emission on diesel engines. There are two NOx sensors, one placed upstream of selective catalytic reduction, to measure inlet NOx concentration, and one placed downstream. They are connected with the control module via CAN and all the information is exchanged through it. Since it is a smart sensor, all the electrical monitoring is performed inside the sensor and only the results are sent to the Engine Control Module (ECM). Each NOx sensor contains a sensing cell, a pumping cell, and a heater. A sample of exhaust gas passes through a diffusion gap between the sensing cell and the pumping cell. The NOx sensor maintains a constant reference voltage across the sensing cell. An electronic circuit within the sensor controls the pump current through the pumping cell in order to maintain a constant voltage in the sensing cell. The amount of current required to maintain the reference voltage in the sensing cell is proportional to the concentration of NOx in the exhaust. The ECM varies the amount of diesel exhaust fluid (reductant) added by varying the reductant injector duty cycle in response to changes in engine exhaust NOx levels. The smart NOx sensors consist of two components, the NOx module and the NOx sensor element that are serviced as a unit. A circuit or performance condition with a NOx sensor is detected by the NOx sensor module. The smart NOx sensor module communicates the condition to the ECM over the serial data line. The ECM sets a DTC when a serial data message is received from the NOx sensor module. The Diagnostic Trouble Code (DTC) will be set if the ECM software detects a fault in the NOx sensor circuitry or a performance fault in the NOx sensor for greater than 2 s.

OBDII Code P11BF Buick - O2 Reference Voltage Circuit Low Voltage (NOx Sensor 2) - AutoCodes.com — P11BF Buick Code - O2 Reference Voltage Circuit Low Voltage (NOx Sensor 2)

What does this mean?

What are the Possible Causes of the DTC P11BF Buick?

Faulty Nitrogen Oxides (NOx) Sensor 2
Nitrogen Oxides Sensor 2 harness is open or shorted
Nitrogen Oxides Sensor 2 circuit poor electrical connection

How to Fix the DTC P11BF Buick?

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 P11BF Buick 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.

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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 P11BF Buick Code

1. What does the OBDII code P11BF mean on a Buick?

The P11BF code indicates an "O2 Reference Voltage Circuit Low Voltage" issue related to NOx Sensor 2, which monitors nitrogen oxide emissions.

2. What are the common symptoms of a P11BF code on a Buick?

Symptoms may include the check engine light turning on, reduced fuel efficiency, poor engine performance, or the vehicle entering limp mode.

3. What causes the P11BF code to appear in a Buick?

Common causes include a faulty NOx sensor 2, damaged wiring or connectors in the O2 reference voltage circuit, or a malfunctioning Engine Control Module (ECM).

4. Can I drive my Buick with a P11BF code?

While it may be possible to drive, itâ€™s not recommended as it can lead to increased emissions, reduced engine efficiency, and potential damage to the catalytic converter.

5. How do I diagnose a P11BF code in a Buick?

Start by checking the NOx sensor 2 wiring and connectors for damage or corrosion. Use a multimeter to test the reference voltage and verify sensor functionality. A scan tool can also help confirm the issue.

6. How is the P11BF code fixed on a Buick?

Repairs may include replacing the NOx sensor 2, repairing or replacing damaged wiring or connectors, or reprogramming or replacing the ECM if necessary.

7. How much does it cost to fix a P11BF code on a Buick?

The cost can vary, but replacing a NOx sensor typically ranges from $300 to $600, including parts and labor. Wiring repairs or ECM replacement may cost more.

8. Can a P11BF code cause long-term damage to my Buick?

If left unresolved, it can lead to higher emissions, possible damage to the catalytic converter, and reduced engine performance over time.

9. What tools are needed to troubleshoot the P11BF code on a Buick?

Youâ€™ll need an OBDII scanner, a multimeter for voltage testing, and possibly a repair manual specific to your Buick model.

10. Is the P11BF code covered under the emissions warranty for my Buick?

It depends on your vehicle's age and mileage. Emissions-related components like NOx sensors are often covered under the federal emissions warranty up to 8 years or 80,000 miles. Check with your dealership.