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P11D2 2018 GMC Sierra Code - O2 Signal Circuit High 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
P11D2 2018 GMC Sierra indicates O2 Signal Circuit High 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 132
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 P11D2 2018 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 P11D2 2018 GMC Sierra - O2 Signal Circuit High Voltage (NOx Sensor 2) - AutoCodes.com
P11D2 2018 GMC Sierra Code - O2 Signal Circuit High Voltage (NOx Sensor 2)
What does this mean?

What are the Possible Causes of the DTC P11D2 2018 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 P11D2 2018 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 P11D2 2018 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 P11D2 2018 GMC Sierra code?

Need more information on how to fix the P11D2 2018 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P11D2 2018 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 P11D2 2018 GMC Sierra Code

1. What does the OBDII code P11D2 mean on a 2018 GMC Sierra?

The P11D2 code indicates a high voltage issue in the O2 signal circuit for NOx Sensor 2, which monitors nitrogen oxide levels in the exhaust.

2. What are the common symptoms of the P11D2 code?

Symptoms may include a check engine light, reduced fuel efficiency, increased emissions, and possibly reduced engine performance.

3. What causes the P11D2 code to appear?

This code can be caused by a faulty NOx Sensor 2, damaged wiring or connectors in the O2 signal circuit, or a malfunctioning engine control module (ECM).

4. Can I drive my 2018 GMC Sierra with the P11D2 code?

While the vehicle may still be drivable, it’s not recommended as it may lead to poor performance, increased emissions, and potential damage to other components.

5. How is the P11D2 code diagnosed?

A technician will use a scan tool to confirm the code, inspect the NOx sensor and related wiring for damage, and test the sensor’s voltage and signal output.

6. How do you fix the P11D2 code on a 2018 GMC Sierra?

Repairs may include replacing the NOx Sensor 2, repairing or replacing damaged wiring, and ensuring proper connections in the O2 signal circuit.

7. How much does it cost to repair the P11D2 code?

The repair cost can vary but typically ranges from $300 to $700, depending on whether the NOx sensor or wiring needs replacement.

8. Can a dirty or clogged exhaust system cause the P11D2 code?

Yes, issues like a clogged catalytic converter or excessive soot buildup can affect NOx sensor readings and trigger the code.

9. Will clearing the P11D2 code with a scan tool fix the issue?

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

10. How can I prevent the P11D2 code from occurring again?

Regular maintenance of the exhaust system, ensuring clean fuel, and promptly addressing any OBDII codes can help prevent this issue.

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