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P22A4 2018 GMC Sierra 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 2018 GMC Sierra 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 154

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 P22A4 2018 GMC Sierra 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 2018 GMC Sierra - NOx Sensor 2 Heater Control Circuit Low Voltage - AutoCodes.com — P22A4 2018 GMC Sierra Code - NOx Sensor 2 Heater Control Circuit Low Voltage

What does this mean?

What are the Possible Causes of the DTC P22A4 2018 GMC Sierra?

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 2018 GMC Sierra?

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 2018 GMC Sierra 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 P22A4 2018 GMC Sierra code?

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Need Help with the 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 P22A4 2018 GMC Sierra Code

What does the OBD-II code P22A4 mean for a 2018 GMC Sierra?

P22A4 indicates a problem with the NOx Sensor 2 Heater Control Circuit, specifically low voltage detected in the circuit.

What are the symptoms of code P22A4 in a 2018 GMC Sierra?

Symptoms may include a check engine light, decreased fuel efficiency, engine hesitation, or reduced performance due to improper NOx sensor operation.

What causes the P22A4 code to appear?

Common causes include a faulty NOx sensor 2 heater, damaged wiring or connectors in the circuit, or a malfunctioning PCM (powertrain control module).

Can I drive my 2018 GMC Sierra with code P22A4?

Driving with this code is possible but not recommended, as it may lead to increased emissions and reduced engine performance.

How is code P22A4 diagnosed?

A technician will typically inspect the NOx sensor 2, wiring, and connectors for damage, and perform voltage and continuity tests on the heater control circuit.

What repairs are needed to fix P22A4?

Repairs may include replacing the NOx sensor 2, repairing damaged wiring or connectors, or reprogramming or replacing the PCM if necessary.

How much does it cost to fix a P22A4 code on a 2018 GMC Sierra?

Repair costs vary, but replacing the NOx sensor can range from $300 to $800, depending on parts and labor. Wiring repairs may cost less.

Can a faulty NOx sensor cause other problems?

Yes, a faulty NOx sensor can affect engine performance, increase emissions, and potentially damage other components like the catalytic converter.

How do I prevent the P22A4 code from reoccurring?

Regular maintenance, inspecting wiring and connectors for damage, and using high-quality fuel can help prevent issues with the NOx sensor heater circuit.

Is it necessary to clear the P22A4 code after repairs?

Yes, after repairs, the code should be cleared using an OBD-II scanner to ensure the issue has been resolved and the check engine light stays off.