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P11D9 Cadillac 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 Cadillac 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 380

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

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

What does this mean?

What are the Possible Causes of the DTC P11D9 Cadillac?

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 Cadillac?

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 Cadillac 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 Cadillac 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 Cadillac Code

1. What are the common symptoms of OBDII code P11D9 in a Cadillac related to the O2 Pump Current Control Circuit Low Voltage (NOx Sensor 2)?

The common symptoms include poor engine performance, reduced fuel efficiency, and the illumination of the check engine light.

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

Possible causes include a faulty NOx sensor, wiring issues, a defective O2 pump, or a problem with the engine control module.

3. How can I diagnose the O2 Pump Current Control Circuit Low Voltage issue in my Cadillac?

Diagnosis involves using an OBDII scanner to retrieve the trouble code, inspecting the NOx sensor and its wiring, testing the O2 pump, and checking for any loose connections.

4. Can driving with OBDII code P11D9 cause further damage to my Cadillac?

Continued driving with this code may result in decreased engine efficiency, potential damage to the catalytic converter, and increased emissions.

5. How can I repair the O2 Pump Current Control Circuit Low Voltage issue in my Cadillac?

Repair may involve replacing the NOx sensor, repairing or replacing damaged wiring, fixing the O2 pump, or reprogramming the engine control module.

6. Is it safe to drive my Cadillac with the check engine light on due to code P11D9?

It is generally not recommended to drive with the check engine light on, as it indicates a potential issue that requires attention to prevent further damage to the vehicle.

7. Can a DIY enthusiast fix the OBDII code P11D9 issue in a Cadillac?

DIY enthusiasts with automotive repair knowledge and the necessary tools may be able to address the issue, but it is recommended to consult a professional mechanic for an accurate diagnosis and proper repair.

8. How much does it typically cost to repair OBDII code P11D9 in a Cadillac?

The cost of repair can vary depending on the exact cause of the issue, but it may range from a few hundred to over a thousand dollars, including parts and labor.

9. Will resetting the check engine light resolve OBDII code P11D9 in a Cadillac?

Resetting the check engine light will clear the code temporarily, but it will not fix the underlying issue causing the O2 Pump Current Control Circuit Low Voltage fault.

10. How often should I have my Cadillac's NOx sensor and O2 pump inspected to prevent OBDII code P11D9?

Regular maintenance and inspections as per the manufacturer's recommendations can help prevent issues like O2 Pump Current Control Circuit Low Voltage, so it is advisable to follow the service schedule provided in the owner's manual.