AutoCodes – Generic – P11D9

P11D9 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 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 1,658

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 P11D9 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 - O2 Pump Current Control Circuit Low Voltage (NOx Sensor 2) - AutoCodes.com — P11D9 Code - O2 Pump Current Control Circuit Low Voltage (NOx Sensor 2)

What does this mean?

What are the Possible Causes of the DTC P11D9?

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?

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 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 code?

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Need Help with the Code?

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Information for Specific Makes

P11D9 Buick — O2 Pump Current Control Circuit Low Voltage (NOx Sensor 2)
P11D9 Cadillac — O2 Pump Current Control Circuit Low Voltage (NOx Sensor 2)
P11D9 Chevrolet — O2 Pump Current Control Circuit Low Voltage (NOx Sensor 2)
P11D9 GMC — O2 Pump Current Control 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 P11D9 Code

1. What are the common symptoms of OBDII code P11D9 (O2 Pump Current Control Circuit Low Voltage)?

- Common symptoms include poor engine performance, decreased fuel efficiency, rough idling, and the illumination of the Check Engine Light.

2. What are the possible causes of OBDII code P11D9?

- Possible causes of this code include a faulty NOx sensor, damaged wiring or connectors in the O2 pump current control circuit, a malfunctioning O2 pump, or issues with the power supply to the sensor.

3. How can I diagnose OBDII code P11D9?

- To diagnose this code, you can use an OBDII scanner to retrieve the specific fault codes. Additionally, a thorough visual inspection of the NOx sensor wiring and connectors can help identify any visible damage.

4. What are the recommended repair tips for OBDII code P11D9?

- Repair tips may include checking and repairing any damaged wiring or connectors in the O2 pump current control circuit, testing and possibly replacing the NOx sensor, or addressing any issues with the O2 pump itself.

5. Can I drive my vehicle with OBDII code P11D9?

- It is not recommended to drive your vehicle with this code present, as it can lead to further damage to the engine and emissions system. It is best to address the underlying issue promptly.

6. How much does it typically cost to repair OBDII code P11D9?

- The cost of repairing this code can vary depending on the exact cause of the issue, the extent of the damage, and the labor rates in your area. It is advisable to consult with a professional mechanic for a more accurate estimate.

7. Will resetting the Check Engine Light resolve OBDII code P11D9?

- Simply resetting the Check Engine Light may temporarily turn it off, but the underlying issue causing the code will still remain. It is important to diagnose and repair the root cause of the problem to prevent further issues.

8. How often does OBDII code P11D9 occur in vehicles?

- This specific OBDII code may not be as common as some others, but it can still occur in vehicles equipped with NOx sensors and O2 pump current control circuits.

9. Can a DIY enthusiast repair OBDII code P11D9?

- Depending on the skill level and experience of the individual, some DIY enthusiasts may be able to address this code by following repair guides and utilizing the necessary tools. However, it is recommended to seek professional help if unsure.

10. Are there any preventative measures to avoid OBDII code P11D9?

- Regular maintenance, such as checking and replacing sensors and components as recommended by the manufacturer, can help prevent issues that may trigger this code. Additionally, driving responsibly and avoiding rough driving conditions can also help maintain the health of the vehicle's systems.