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P11FD 2014 GMC Sierra Code - O2 Low Reference 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: P11FD 2014 GMC Sierra indicates O2 Low Reference 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 170

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 P11FD 2014 GMC Sierra 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 P11FD 2014 GMC Sierra - O2 Low Reference Circuit Low Voltage (NOx Sensor 2) - AutoCodes.com — P11FD 2014 GMC Sierra Code - O2 Low Reference Circuit Low Voltage (NOx Sensor 2)

What does this mean?

What are the Possible Causes of the DTC P11FD 2014 GMC Sierra?

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 P11FD 2014 GMC Sierra?

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 P11FD 2014 GMC Sierra 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 P11FD 2014 GMC Sierra 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 P11FD 2014 GMC Sierra Code

What does the OBDII code P11FD mean on a 2014 GMC Sierra?

P11FD indicates an issue with the O2 low reference circuit, specifically low voltage detected in NOx sensor 2, which monitors nitrogen oxide emissions.

What are the symptoms of a P11FD code in a 2014 GMC Sierra?

Common symptoms include an illuminated check engine light, reduced fuel efficiency, potential power loss, and possible limp mode activation.

What causes the P11FD code to appear?

Causes include faulty NOx sensor 2, damaged wiring or connectors, corrosion in the circuit, or a malfunctioning engine control module (ECM).

Can I drive my 2014 GMC Sierra with a P11FD code?

Driving is possible but not recommended, as it could lead to increased emissions, reduced performance, or further damage to the vehicle's exhaust system.

How do I diagnose a P11FD code?

Inspect the NOx sensor 2, check for damaged wiring or connectors, test the low reference circuit for continuity, and use a scan tool to monitor sensor voltage readings.

How do I fix the P11FD code on a 2014 GMC Sierra?

Repairs may include replacing the NOx sensor 2, repairing damaged wiring, cleaning corroded connectors, or reprogramming/updating the ECM if needed.

How much does it cost to fix a P11FD code?

Costs vary but typically range from $200 to $600 for parts and labor, depending on whether the NOx sensor or wiring needs replacement.

Can a faulty NOx sensor cause the P11FD code?

Yes, a faulty NOx sensor 2 is one of the primary causes of this code and should be tested and replaced if necessary.

What tools are needed to troubleshoot the P11FD code?

Youâ€™ll need a scan tool with OBDII capabilities, a multimeter for voltage testing, and potentially a wiring diagram for your vehicle.

Is the P11FD code covered under warranty for a 2014 GMC Sierra?

It may be covered under the emissions warranty, depending on your vehicle's mileage and specific warranty terms. Check with your dealership for details.