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P21B3 Dodge Code - Closed Loop NOx Absorber At Limit Too High

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 Mass Air Flow (MAF) Sensor value not learned, EGR valve sticking or restricted, Thermostat outlet restricted. 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
P21B3 Dodge indicates Closed Loop NOx Absorber At Limit Too High.
Common causes
Common causes include Mass Air Flow (MAF) Sensor value not learned, EGR valve sticking or restricted, Thermostat outlet restricted.
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 840
How popular is this code, among other codes? Low
What is this?
Table of contents Created and updated by William Orellana on Aug 09, 2020
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Code P21B3 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 if the time duration after an active soot regeneration is requested exceeds a calibrated threshold and the Diesel Oxidation Catalyst inlet temperature has not reached the light-off temperature threshold to begin closed-loop control.
OBDII Code P21B3 Dodge - Closed Loop NOx Absorber At Limit Too High - AutoCodes.com
P21B3 Dodge Code - Closed Loop NOx Absorber At Limit Too High
What does this mean?

What are the Possible Causes of the DTC P21B3 Dodge?

  • Mass Air Flow (MAF) Sensor value not learned
  • EGR valve sticking or restricted
  • Thermostat outlet restricted
  • Faulty EGR cooler bypass control valve
  • Faulty EGR airflow control valve
  • Leaking or damaged NOx absorber catalyst

How to Fix the DTC P21B3 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 P21B3 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.

Need more information about the P21B3 Dodge 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 P21B3 Dodge Code

1. What does the OBDII code P21B3 mean on a Dodge?

The P21B3 code indicates that the closed-loop NOx absorber system has detected NOx levels that are too high, suggesting the system is not operating efficiently.

2. What are the common symptoms of a P21B3 code?

Symptoms may include the check engine light turning on, reduced engine performance, increased emissions, and potentially lower fuel efficiency.

3. What causes the P21B3 code to appear?

Common causes include a faulty NOx sensor, a malfunctioning NOx absorber, issues with the exhaust system, or software-related problems in the engine control module (ECM).

4. Can I drive my Dodge with a P21B3 code?

Driving with this code is not recommended as it can lead to higher emissions, potential damage to the NOx absorber, and reduced fuel efficiency.

5. How is the P21B3 code diagnosed?

Diagnosis typically involves scanning for codes, inspecting the NOx sensor and absorber system, checking for exhaust leaks, and verifying proper ECM operation.

6. How can I fix the P21B3 code on my Dodge?

Repairs may include replacing a faulty NOx sensor, servicing or replacing the NOx absorber, repairing exhaust leaks, or updating the ECM software.

7. Is a faulty NOx sensor a common issue with the P21B3 code?

Yes, a faulty NOx sensor is a frequent cause of this code, as it can provide inaccurate data to the ECM.

8. How much does it cost to fix a P21B3 code?

Repair costs vary but may range from $200 to $800 depending on whether the NOx sensor, absorber, or another component needs replacement.

9. Can an exhaust leak trigger the P21B3 code?

Yes, exhaust leaks can interfere with NOx sensor readings, potentially causing this code to appear.

10. Will clearing the code fix the P21B3 issue?

Clearing the code without addressing the underlying problem will not fix the issue, and the code is likely to return.

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