AutoCodes – Generic – P22A9

P22A9 Code - NOx Sensor 2 Heater Feedback Circuit Low Voltage

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: P22A9 indicates NOx Sensor 2 Heater Feedback Circuit Low Voltage.
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 1,276

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 P22A9 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 P22A9 - NOx Sensor 2 Heater Feedback Circuit Low Voltage - AutoCodes.com — P22A9 Code - NOx Sensor 2 Heater Feedback Circuit Low Voltage

What does this mean?

What are the Possible Causes of the DTC P22A9?

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 P22A9?

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 P22A9 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 P22A9 code?

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Need Help with the Code?

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Information for Specific Makes

P22A9 Buick — NOx Sensor 2 Heater Feedback Circuit Low Voltage
P22A9 Cadillac — NOx Sensor 2 Heater Feedback Circuit Low Voltage
P22A9 Chevrolet — NOx Sensor 2 Heater Feedback Circuit Low Voltage
P22A9 GMC — NOx Sensor 2 Heater Feedback Circuit Low Voltage

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 P22A9 Code

1. What are common symptoms of OBDII code P22A9 (NOx Sensor 2 Heater Feedback Circuit Low Voltage)?

- Common symptoms include poor engine performance, decreased fuel efficiency, and illuminated Check Engine Light.

2. What can cause OBDII code P22A9 to trigger?

- This code is typically triggered by a malfunction in the NOx Sensor 2 heater feedback circuit, leading to low voltage feedback.

3. How serious is OBDII code P22A9 (NOx Sensor 2 Heater Feedback Circuit Low Voltage)?

- While the vehicle may still be operable with this code, it is important to address it promptly to prevent potential damage to the catalytic converter and ensure optimal engine performance.

4. Can driving with OBDII code P22A9 cause further damage to the vehicle?

- Continuing to drive with this code may lead to increased emissions, reduced fuel efficiency, and potential long-term damage to the vehicle's emission control system.

5. How can I diagnose the issue causing OBDII code P22A9?

- Diagnosis typically involves using an OBDII scanner to read the code, inspecting the NOx Sensor 2 heater circuit for faults, and testing the sensor's voltage feedback.

6. What are some possible repair tips for fixing OBDII code P22A9?

- Repair options may include checking and repairing wiring connections, replacing the NOx Sensor 2 heater, or addressing any underlying electrical issues causing the low voltage feedback.

7. Is it possible to reset OBDII code P22A9 without fixing the underlying issue?

- While clearing the code may temporarily turn off the Check Engine Light, it is crucial to address the root cause of the problem to prevent it from recurring.

8. Can a DIY enthusiast repair OBDII code P22A9 at home?

- Depending on the individual's skill level and access to tools, some DIY enthusiasts may be able to address this code by following repair guides and tutorials. However, professional diagnosis and repair are recommended for complex issues.

9. How much does it typically cost to fix OBDII code P22A9 at a mechanic or dealership?

- The cost of repairing this code can vary depending on the extent of the issue, parts needed, labor rates, and whether the repair is done at a mechanic or dealership. It is advisable to obtain quotes from multiple sources.

10. Are there any preventative maintenance measures to avoid OBDII code P22A9 in the future?

- Regularly servicing the vehicle, maintaining proper engine performance, and addressing any warning signs promptly can help prevent issues like OBDII code P22A9 from occurring.