AutoCodes – Dodge – P21B4 Dodge

P21B4 Dodge Code - NOx Absorber Over Temperature

Quick Answer

When the engine runs in DeNOx mode, the Powertrain Control Module (PCM) monitors how much post-injection fuel has been injected. Common causes include Exhaust Temperature Sensors failed in-range low, Unintended fueling, Damaged NOx absorber catalyst. 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: P21B4 Dodge indicates NOx Absorber Over Temperature.
Common causes: Common causes include Exhaust Temperature Sensors failed in-range low, Unintended fueling, Damaged NOx absorber catalyst.
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 518

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 Aug 09, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P21B4 Dodge Description

When the engine runs in DeNOx mode, the Powertrain Control Module (PCM) monitors how much post-injection fuel has been injected. Once it exceeds a threshold, the measured O2 Sensor 1/1 is supposed to be lower than a threshold. If after a sufficient amount of post fuel is injected, the O2 Sensor 1/1 value is still high for a calibrated time, the fail counter is incremented by 1. If it is not, it is decremented by 1. If the counter has been incremented or decremented for a calibrated number of times, and the counter value is greater than a calibrated value, this fault is set. The Diagnostic Trouble Code (DTC) will set when the NAC outlet temperature exceeds a calibrated high threshold for a calibrated period of time.

OBDII Code P21B4 Dodge - NOx Absorber Over Temperature - AutoCodes.com — P21B4 Dodge Code - NOx Absorber Over Temperature

What does this mean?

What are the Possible Causes of the DTC P21B4 Dodge?

Exhaust Temperature Sensors failed in-range low
Unintended fueling
Damaged NOx absorber catalyst

How to Fix the DTC P21B4 Dodge?

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 P21B4 Dodge 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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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 P21B4 Dodge Code

1. What are the common symptoms of OBDII code P21B4 Dodge (NOx Absorber Over Temperature)?

- Common symptoms include the check engine light coming on, reduced engine performance, and potential exhaust system issues.

2. What can cause the OBDII code P21B4 Dodge to trigger?

- This code is typically triggered when the NOx absorber reaches an over-temperature condition due to exhaust system malfunctions or sensor failures.

3. How serious is the NOx Absorber Over Temperature fault code?

- This fault code should be addressed promptly as it can lead to increased emissions, potential damage to the catalytic converter, and decreased fuel efficiency.

4. Can driving with the P21B4 code present cause further damage to the vehicle?

- Continuing to drive with this fault code may cause additional stress on the exhaust system components and lead to more severe engine issues over time.

5. What are some DIY repair tips for OBDII code P21B4 Dodge?

- DIY repair tips include checking for exhaust leaks, inspecting the NOx sensor, and ensuring proper operation of the NOx absorber system components.

6. How can I reset the OBDII code P21B4 Dodge after making repairs?

- The code can be reset using an OBDII scanner or by disconnecting the vehicle's battery for a few minutes to clear the fault code.

7. Can a faulty NOx absorber be cleaned or repaired, or does it need to be replaced?

- In some cases, cleaning the NOx absorber or replacing faulty components like sensors may resolve the issue. However, severe damage may require a full replacement.

8. Is it safe to drive my vehicle with the NOx Absorber Over Temperature fault code temporarily cleared?

- It is generally safe to drive the vehicle after clearing the code, but it is important to monitor for any recurring symptoms or issues that may indicate a persistent problem.

9. How much does it typically cost to repair the NOx Absorber Over Temperature fault code?

- Repair costs can vary depending on the extent of the damage and whether components need to be repaired or replaced. It is recommended to consult a mechanic for an accurate estimate.

10. Are there any preventative maintenance steps I can take to avoid OBDII code P21B4 Dodge in the future?

- Regularly inspecting and maintaining the exhaust system, monitoring for unusual engine behavior, and addressing any warning lights promptly can help prevent this fault code from occurring.