AutoCodes – Generic – P22A8

P22A8 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: P22A8 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 1,378

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 P22A8 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 P22A8 - NOx Sensor 2 Heater Feedback Circuit Low Voltage - AutoCodes.com — P22A8 Code - NOx Sensor 2 Heater Feedback Circuit Low Voltage

What does this mean?

What are the Possible Causes of the DTC P22A8?

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 P22A8?

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 P22A8 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 P22A8 code?

Need more information on how to fix the P22A8 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P22A8 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

P22A8 Buick — NOx Sensor 2 Heater Feedback Circuit Low Voltage
P22A8 Cadillac — NOx Sensor 2 Heater Feedback Circuit Low Voltage
P22A8 Chevrolet — NOx Sensor 2 Heater Feedback Circuit Low Voltage
P22A8 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 P22A8 Code

1. What are the common symptoms of OBDII code P22A8?

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

2. What does the NOx Sensor 2 Heater Feedback Circuit Low Voltage mean?

- It indicates that the electrical circuit responsible for heating the NOx sensor 2 is experiencing low voltage.

3. What are the possible causes of the NOx Sensor 2 Heater Feedback Circuit Low Voltage code?

- Potential causes include a faulty NOx sensor, damaged wiring or connectors, a defective heater circuit, or a problem with the vehicle's ECM.

4. How can I diagnose the NOx Sensor 2 Heater Feedback Circuit Low Voltage issue?

- Diagnosis typically involves inspecting the sensor and its wiring, checking for continuity in the heater circuit, and using a scan tool to monitor sensor data.

5. Can I drive my vehicle with the P22A8 code?

- It is not recommended to drive the vehicle with this code active, as it can lead to increased emissions and potential damage to the catalytic converter.

6. How can I repair the NOx Sensor 2 Heater Feedback Circuit Low Voltage problem?

- Repair options may include replacing the NOx sensor, repairing damaged wiring or connectors, addressing issues with the heater circuit, or reprogramming the ECM.

7. Are there any DIY tips for fixing the P22A8 code?

- DIY repairs for this code may be challenging and require specialized tools. It is recommended to consult a professional mechanic for proper diagnosis and repair.

8. How much does it cost to fix the NOx Sensor 2 Heater Feedback Circuit Low Voltage issue?

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

9. Can a faulty NOx sensor cause other problems in the vehicle?

- Yes, a faulty NOx sensor can affect the vehicle's emissions output, fuel efficiency, and overall engine performance if not addressed promptly.

10. How can I prevent the NOx Sensor 2 Heater Feedback Circuit Low Voltage code from recurring?

- Regular maintenance, avoiding harsh driving conditions, and addressing any related issues promptly can help prevent the reoccurrence of this code.

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