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P11D9 2017 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 2017 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 127
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 2017 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 2017 GMC Sierra - O2 Pump Current Control Circuit Low Voltage (NOx Sensor 2) - AutoCodes.com
P11D9 2017 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 2017 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 2017 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 2017 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 2017 GMC Sierra code?

Need more information on how to fix the P11D9 2017 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the 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 P11D9 2017 GMC Sierra Code

What does the OBD-II code P11D9 indicate on a 2017 GMC Sierra?

Code P11D9 indicates that the O2 pump current control circuit for NOx Sensor 2 is experiencing low voltage, which may affect the vehicle's emissions control system.

What are common symptoms of the P11D9 code?

Symptoms may include the check engine light turning on, reduced fuel efficiency, poor engine performance, or higher emissions levels.

What causes the P11D9 code to appear?

Common causes include a faulty NOx sensor 2, wiring or connector issues in the O2 pump control circuit, or a malfunctioning engine control module (ECM).

Can driving with the P11D9 code cause damage?

While driving with this code may not immediately damage the engine, prolonged issues with the NOx sensor can lead to increased emissions and potentially damage other components.

How is the P11D9 code diagnosed?

A mechanic will use a diagnostic scanner to verify the code, inspect the NOx sensor and related wiring, and test the pump current control circuit for proper functionality.

How can the P11D9 code be repaired?

Repairs may involve replacing the NOx sensor 2, repairing or replacing damaged wiring, or updating/reprogramming the ECM.

How much does it cost to fix the P11D9 code on a 2017 GMC Sierra?

Repair costs can range from $200 to $600, depending on whether the NOx sensor or wiring needs replacement.

Can I clear the P11D9 code without fixing the issue?

Clearing the code without addressing the underlying problem may temporarily turn off the check engine light, but the code is likely to return.

How do I prevent the P11D9 code from occurring again?

Regular maintenance, inspecting wiring for damage, and using high-quality fuel can help prevent NOx sensor-related issues.

Is the NOx sensor under warranty for a 2017 GMC Sierra?

The NOx sensor may be covered under the emissions warranty. Check your vehicle's warranty details or contact your dealership for confirmation.

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