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P11D9 2015 GMC Sierra Code - O2 Pump Current Control 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
P11D9 2015 GMC Sierra indicates O2 Pump Current Control 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 153
How popular is this code, among other codes? Low
What is this?
Table of contents Created and updated by William Orellana on Mar 24, 2024
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Code P11D9 2015 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 P11D9 2015 GMC Sierra - O2 Pump Current Control Circuit Low Voltage (NOx Sensor 2) - AutoCodes.com
P11D9 2015 GMC Sierra Code - O2 Pump Current Control Circuit Low Voltage (NOx Sensor 2)
What does this mean?

What are the Possible Causes of the DTC P11D9 2015 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 P11D9 2015 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 P11D9 2015 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 P11D9 2015 GMC Sierra code?

Need more information on how to fix the P11D9 2015 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P11D9 2015 GMC Sierra 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 P11D9 2015 GMC Sierra Code

1. What does the OBDII code P11D9 mean on a 2015 GMC Sierra?

P11D9 indicates a low voltage issue in the O2 Pump Current Control Circuit for NOx Sensor 2, which monitors and controls nitrogen oxide emissions.

2. What are the common symptoms of a P11D9 code on a GMC Sierra?

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 P11D9 code to appear on a 2015 GMC Sierra?

Common causes include a faulty NOx sensor 2, damaged wiring or connectors in the sensor circuit, or issues with the engine control module (ECM).

4. Can I drive my 2015 GMC Sierra with a P11D9 code?

Driving with a P11D9 code is not recommended as it can lead to increased emissions, reduced engine performance, and potential damage to other components.

5. How do I diagnose the P11D9 code on a GMC Sierra?

Diagnosis involves using a scan tool to verify the code, inspecting the NOx sensor 2 and its wiring for damage, and testing the circuit voltage to confirm the issue.

6. How is the P11D9 code fixed on a 2015 GMC Sierra?

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

7. How much does it cost to fix a P11D9 code on a GMC Sierra?

Costs vary, but replacing a NOx sensor can range from $300 to $700, while wiring repairs and ECM replacement may add additional costs.

8. What tools do I need to troubleshoot the P11D9 code?

A professional-grade OBDII scan tool, a multimeter, and basic hand tools are essential for diagnosing and repairing this code.

9. Can a dirty or clogged NOx sensor cause the P11D9 code?

While a dirty sensor is less common, it’s possible. However, the code is more often caused by electrical issues or sensor failure.

10. Will clearing the P11D9 code with a scan tool fix the issue?

Clearing the code may turn off the check engine light temporarily, but the underlying problem must be fixed to prevent the code from returning.

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