AutoCodes – Generic – P22A4

P22A4 Code - NOx Sensor 2 Heater Control 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: P22A4 indicates NOx Sensor 2 Heater Control 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 2,305

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 P22A4 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 P22A4 - NOx Sensor 2 Heater Control Circuit Low Voltage - AutoCodes.com — P22A4 Code - NOx Sensor 2 Heater Control Circuit Low Voltage

What does this mean?

What are the Possible Causes of the DTC P22A4?

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 P22A4?

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 P22A4 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.

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Information for Specific Makes

P22A4 Buick — NOx Sensor 2 Heater Control Circuit Low Voltage
P22A4 Cadillac — NOx Sensor 2 Heater Control Circuit Low Voltage
P22A4 Chevrolet — NOx Sensor 2 Heater Control Circuit Low Voltage
P22A4 GMC — NOx Sensor 2 Heater Control 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 P22A4 Code

1. What are the common symptoms of OBDII code P22A4 (NOx Sensor 2 Heater Control Circuit Low Voltage)?

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

2. What are the possible causes of OBDII code P22A4?

- The code P22A4 can be triggered by a faulty NOx sensor 2 heater, damaged wiring or connectors in the sensor circuit, or a malfunctioning powertrain control module (PCM).

3. How can I diagnose OBDII code P22A4?

- Diagnosing code P22A4 involves using an OBDII scanner to retrieve the code, inspecting the NOx sensor 2 heater circuit for any visible issues, and testing the sensor and related components for proper functionality.

4. Can I continue driving with OBDII code P22A4 present?

- It is not recommended to continue driving with code P22A4 present, as it can lead to further damage to the engine and emissions system. It is best to address the issue promptly.

5. How can I repair OBDII code P22A4?

- Repairing code P22A4 typically involves replacing the faulty NOx sensor 2 heater, repairing any damaged wiring or connectors, or reprogramming the PCM if necessary.

6. Are there any DIY tips for fixing OBDII code P22A4?

- DIY tips for fixing code P22A4 include carefully inspecting the sensor and its connections for any visible issues, checking the fuses related to the sensor circuit, and ensuring proper grounding of the sensor.

7. How much does it cost to repair OBDII code P22A4?

- The cost of repairing code P22A4 can vary depending on the root cause of the issue, the cost of parts, and labor charges. It is recommended to obtain quotes from different mechanics or repair shops for an accurate estimate.

8. Can a faulty NOx sensor cause other issues besides triggering code P22A4?

- Yes, a faulty NOx sensor can lead to other issues such as increased emissions, failed emissions tests, and potential damage to the catalytic converter and other engine components if left unresolved.

9. Is it safe to reset the check engine light after repairing OBDII code P22A4?

- It is safe to reset the check engine light after repairing code P22A4, as long as the underlying issue has been properly addressed. Resetting the light allows you to monitor if the code reappears, indicating any lingering problems.

10. How can I prevent OBDII code P22A4 from recurring in the future?

- To prevent code P22A4 from recurring, it is important to perform regular maintenance on your vehicle, including checking the NOx sensor 2 heater circuit during routine inspections and addressing any issues promptly to avoid further complications.