AutoCodes – GMC – P11FD GMC

P11FD GMC 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 GMC 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 486

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

What does this mean?

What are the Possible Causes of the DTC P11FD GMC?

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 GMC?

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 GMC 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 GMC code?

Need more information on how to fix the P11FD GMC code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P11FD GMC code diagnosed by a professional: Find a repair shop in your area

Information for Specific GMC Models

P11FD 2014 GMC Sierra — O2 Low Reference Circuit Low Voltage (NOx Sensor 2)
P11FD 2015 GMC Sierra — O2 Low Reference Circuit Low Voltage (NOx Sensor 2)
P11FD 2016 GMC Sierra — O2 Low Reference Circuit Low Voltage (NOx Sensor 2)
P11FD 2017 GMC Sierra — O2 Low Reference Circuit Low Voltage (NOx Sensor 2)
P11FD 2018 GMC Sierra — O2 Low Reference Circuit Low Voltage (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 P11FD GMC Code

1. What are the common symptoms of OBDII code P11FD GMC (O2 Low Reference Circuit Low Voltage for NOx Sensor 2)?

- Common symptoms include poor engine performance, decreased fuel efficiency, and illuminated Check Engine Light.

2. What are the possible causes of OBDII code P11FD GMC?

- Possible causes may include a faulty NOx sensor, damaged wiring or connectors in the O2 sensor circuit, or issues with the NOx sensor heater.

3. How can I diagnose OBDII code P11FD GMC?

- Diagnosis typically involves using a scan tool to read the code, checking the wiring and connectors for damage, and testing the NOx sensor's functionality.

4. Can a DIY enthusiast repair OBDII code P11FD GMC?

- Repairing this code may require advanced automotive knowledge and specialized tools. It is recommended to consult a professional mechanic for proper diagnosis and repair.

5. What are the repair tips for addressing OBDII code P11FD GMC?

- Repair tips may include checking and repairing any damaged wiring or connectors, testing the NOx sensor's operation, and resetting the code after repairs are made.

6. Is it safe to continue driving with OBDII code P11FD GMC?

- It is not recommended to continue driving with this code as it may lead to further damage to the vehicle's emissions system and affect overall engine performance.

7. How much does it cost to fix OBDII code P11FD GMC?

- The cost of fixing this code can vary depending on the specific issue causing it. Repair costs may include parts replacement, labor, and diagnostic fees.

8. Can extreme weather conditions trigger OBDII code P11FD GMC?

- Extreme weather conditions, such as extreme cold or heat, can potentially affect the NOx sensor's operation and trigger this code.

9. How often does OBDII code P11FD GMC occur in GMC vehicles?

- The occurrence of this specific code can vary among GMC vehicles, but it is not a common issue compared to other OBDII codes.

10. Are there any recalls related to OBDII code P11FD GMC?

- It is advisable to check with the manufacturer or authorized GMC service centers for any recalls related to OBDII code P11FD and related issues.

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