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P11D8 2018 GMC Sierra Code - O2 Pump Current Control Circuit (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
P11D8 2018 GMC Sierra indicates O2 Pump Current Control Circuit (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 268
How popular is this code, among other codes? Low
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Table of contents Created and updated by William Orellana on Mar 24, 2024
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Code P11D8 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 P11D8 2018 GMC Sierra - O2 Pump Current Control Circuit (NOx Sensor 2) - AutoCodes.com
P11D8 2018 GMC Sierra Code - O2 Pump Current Control Circuit (NOx Sensor 2)
What does this mean?

What are the Possible Causes of the DTC P11D8 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 P11D8 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 P11D8 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 P11D8 2018 GMC Sierra code?

Need more information on how to fix the P11D8 2018 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P11D8 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 P11D8 2018 GMC Sierra Code

1. What does the OBDII code P11D8 mean on a 2018 GMC Sierra?

P11D8 refers to an issue with the O2 pump current control circuit for NOx Sensor 2, which monitors and regulates emissions-related components in the exhaust system.

2. What are the symptoms of the P11D8 code in a 2018 GMC Sierra?

Common symptoms include an illuminated check engine light, reduced engine performance, increased emissions, and possibly poor fuel efficiency.

3. What causes the P11D8 code to appear on my GMC Sierra?

Potential causes include a faulty NOx Sensor 2, damaged wiring in the O2 pump circuit, a malfunctioning ECM, or poor electrical connections.

4. Can I drive my 2018 GMC Sierra with the P11D8 code active?

While the truck may still be drivable, it’s not recommended as it can lead to higher emissions, reduced performance, or damage to other components if left unresolved.

5. How do I diagnose the P11D8 code on my GMC Sierra?

Start by scanning for other related codes, inspecting the wiring and connectors for damage, testing the NOx sensor functionality, and checking the ECM for faults.

6. How do I fix the P11D8 code on a 2018 GMC Sierra?

Repairs may include replacing the NOx Sensor 2, repairing or replacing damaged wiring, cleaning electrical connectors, or reprogramming or replacing the ECM if necessary.

7. How much does it cost to fix the P11D8 code?

The repair cost varies, but replacing a NOx sensor typically ranges from $300 to $800, depending on parts and labor rates.

8. Can a bad NOx Sensor 2 trigger other codes in a GMC Sierra?

Yes, a faulty NOx sensor can cause additional codes related to emissions, fuel mixture, and exhaust system malfunctions.

9. How do I prevent the P11D8 code from recurring?

Regular maintenance, including inspecting and cleaning exhaust components and electrical connections, can help prevent this code from reappearing.

10. Will a software update fix the P11D8 code on a 2018 GMC Sierra?

In some cases, a software update for the ECM may resolve the issue, but this depends on the root cause of the code.

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