AutoCodes – Generic – P11FC

P11FC Code - O2 Low Reference Circuit (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: P11FC indicates O2 Low Reference Circuit (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 857

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 Mar 24, 2024

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P11FC 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 P11FC - O2 Low Reference Circuit (NOx Sensor 2) - AutoCodes.com — P11FC Code - O2 Low Reference Circuit (NOx Sensor 2)

What does this mean?

What are the Possible Causes of the DTC P11FC?

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 P11FC?

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 P11FC 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 P11FC code?

Need more information on how to fix the P11FC code? Get Access to Factory Service Manuals

Need Help with the Code?

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Information for Specific Makes

P11FC Buick — O2 Low Reference Circuit (NOx Sensor 2)
P11FC Cadillac — O2 Low Reference Circuit (NOx Sensor 2)
P11FC Chevrolet — O2 Low Reference Circuit (NOx Sensor 2)
P11FC GMC — O2 Low Reference Circuit (NOx Sensor 2)

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 P11FC Code

1. What are the common symptoms of OBDII code P11FC (O2 Low Reference Circuit - NOx Sensor 2)?

- Common symptoms include poor engine performance, reduced fuel efficiency, and the illumination of the Check Engine Light.

2. What are the typical causes of OBDII code P11FC?

- The code P11FC is often triggered by issues such as a faulty NOx sensor, damaged wiring or connectors, or a malfunctioning powertrain control module (PCM).

3. How can I diagnose the O2 Low Reference Circuit issue related to NOx Sensor 2?

- Diagnosis often involves using a diagnostic scanner to retrieve the specific fault code, inspecting the wiring and connectors for damage, and testing the NOx sensor for proper functionality.

4. Can a DIY enthusiast repair OBDII code P11FC at home?

- While some basic troubleshooting like checking the wiring connections can be done at home, diagnosing and repairing the underlying issues may require professional equipment and expertise.

5. What are the potential consequences of ignoring OBDII code P11FC?

- Ignoring this code can lead to increased emissions, potential damage to other components, and failing an emissions test, which may result in legal issues in some areas.

6. Is it safe to continue driving with OBDII code P11FC present?

- It is not recommended to drive with this code active, as it can lead to reduced engine performance and fuel efficiency, potentially causing further damage to the vehicle.

7. Can a bad NOx sensor cause OBDII code P11FC?

- Yes, a malfunctioning NOx sensor, particularly NOx Sensor 2, can trigger the O2 Low Reference Circuit code P11FC.

8. How much does it typically cost to repair OBDII code P11FC?

- The cost of repairing this code can vary depending on the specific issue, but it may range from $200 to $800, including parts and labor.

9. Are there any common temporary fixes for OBDII code P11FC?

- Temporary fixes like clearing the code using a diagnostic scanner may temporarily turn off the Check Engine Light, but they will not address the underlying issue causing the code.

10. How long does it usually take to repair OBDII code P11FC?

- The repair time for this code can vary based on the extent of the issue and the availability of parts, but it typically takes a few hours to a full day at a repair shop.