AutoCodes – Dodge – P21B2 Dodge

P21B2 Dodge Code - Excessive Time To Enter Closed Loop NOx Absorber Control

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: P21B2 Dodge indicates Excessive Time To Enter Closed Loop NOx Absorber Control.
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 953

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 P21B2 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, during post fuel injection, the O2 Sensor 1/1 value is above a calibrated threshold a fail count is recorded as incremented. If not, it is recorded as decremented. After a calibrated number of total counts (incremented and decremented), the counter value is above a calibrated value, a fault is set.

OBDII Code P21B2 Dodge - Excessive Time To Enter Closed Loop NOx Absorber Control - AutoCodes.com — P21B2 Dodge Code - Excessive Time To Enter Closed Loop NOx Absorber Control

What does this mean?

What are the Possible Causes of the DTC P21B2 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 P21B2 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 P21B2 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 P21B2 Dodge Code

What does the OBDII code P21B2 mean for a Dodge vehicle?

P21B2 indicates that the engine control module (ECM) has detected an excessive amount of time to enter closed-loop NOx absorber control, which is part of the emissions system.

What are the common symptoms of a P21B2 code in a Dodge?

Symptoms may include an illuminated check engine light, reduced fuel efficiency, increased emissions, and possible engine hesitation or poor performance.

What causes the P21B2 code to appear?

Possible causes include a malfunctioning NOx sensor, issues with the NOx absorber, exhaust leaks, software problems in the ECM, or faulty wiring in the emissions system.

Can a P21B2 code affect drivability?

Yes, it can cause performance issues, such as reduced engine power or hesitation, and may result in the vehicle failing an emissions test.

How do you diagnose a P21B2 code?

Diagnosis typically involves using an OBDII scanner to confirm the code, inspecting the NOx sensors and absorber for damage, checking for exhaust leaks, and testing the wiring and connectors in the emissions system.

What repairs can fix a P21B2 code?

Repairs may include replacing a faulty NOx sensor, repairing exhaust leaks, updating the ECM software, or replacing the NOx absorber if it is damaged or clogged.

Can a loose or damaged exhaust system trigger the P21B2 code?

Yes, exhaust leaks can affect the NOx absorber's ability to function properly and may cause this code to set.

Is it safe to drive with a P21B2 code?

While the vehicle may still be drivable, ignoring this code can lead to increased emissions, reduced fuel efficiency, and potential damage to the emissions system.

Does the P21B2 code require specialized tools for repair?

Yes, diagnosing and repairing this code often requires an OBDII scanner, a multimeter for testing electrical connections, and potentially advanced tools for emissions testing.

Can a software update resolve the P21B2 code?

In some cases, a software update from the manufacturer may fix calibration issues in the ECM that are causing the code.