AutoCodes – Generic – P221D

P221D Code - Reductant Heater 2 Current Too High

Quick Answer

The Selective Catalyst Reduction (SCR) system reduces Oxides of Nitrogen (NOx) emissions by injecting a metered amount of Diesel Exhaust Fluid (DEF) or reductant into the exhaust gas stream entering the SCR catalyst. Common causes include Faulty Reductant Heater 2, Reductant Heater 2 harness is open or shorted, Reductant Heater 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: P221D indicates Reductant Heater 2 Current Too High.
Common causes: Common causes include Faulty Reductant Heater 2, Reductant Heater 2 harness is open or shorted, Reductant Heater 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 618

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 Sep 10, 2021

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P221D Description

The Selective Catalyst Reduction (SCR) system reduces Oxides of Nitrogen (NOx) emissions by injecting a metered amount of Diesel Exhaust Fluid (DEF) or reductant into the exhaust gas stream entering the SCR catalyst. Within the SCR catalyst, the reductant reacts with the NOx to form nitrogen, carbon dioxide, and water vapor. Upstream and downstream NOx sensors provide the Engine Control Module (ECM) with engine-out and tailpipe-out NOx levels in Parts Per Million (ppm). The ECM then adjusts the amount of reductant injected upstream of the SCR based on the NOx concentration. Engine-out NOx levels as measured by NOx Sensor 1 will either increase (high ppm) or decrease (low ppm) the amount of reductant injected. The NOx concentration as measured by NOx Sensor 2 provides the ECM with both an indication of the NOx conversion efficiency within the SCR as well as confirming the proper operation of the reductant system. The Diagnostic Trouble Code (DTC) will be set when the Glow Plug Control Module (GPCM) detects a heater short circuit by detecting a high current in the heater.

OBDII Code P221D - Reductant Heater 2 Current Too High - AutoCodes.com — P221D Code - Reductant Heater 2 Current Too High

What does this mean?

What are the Possible Causes of the DTC P221D?

Faulty Reductant Heater 2
Reductant Heater 2 harness is open or shorted
Reductant Heater 2 circuit poor electrical connection
Faulty Glow Plug Control Module (GPCM)

How to Fix the DTC P221D?

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 P221D 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 P221D code?

Need more information on how to fix the P221D code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P221D code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

P221D Chevrolet — Reductant Heater 2 Current Too High
P221D GMC — Reductant Heater 2 Current Too High

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 P221D Code

1. What are the common symptoms of OBDII code P221D (Reductant Heater 2 Current Too High)?

- Common symptoms include the check engine light coming on, reduced engine performance, and potential issues with the vehicle's emissions system.

2. What could cause OBDII code P221D to trigger?

- The code P221D may be triggered by a faulty reductant heater 2, a damaged wiring harness, a malfunctioning powertrain control module (PCM), or issues with the reductant heater control circuit.

3. How serious is OBDII code P221D (Reductant Heater 2 Current Too High)?

- While this code may not cause immediate drivability issues, it is important to address it promptly to prevent potential damage to the vehicle's emissions system and ensure compliance with environmental regulations.

4. Can I continue driving with OBDII code P221D active?

- It is generally not recommended to continue driving with the code active, as it can lead to increased emissions and potential damage to the vehicle's catalytic converter over time.

5. What are some repair tips for addressing OBDII code P221D?

- Repair tips may include inspecting and testing the reductant heater 2, checking the wiring harness for damage, verifying the operation of the PCM, and ensuring proper functioning of the reductant heater control circuit.

6. How can I diagnose OBDII code P221D at home?

- Diagnosing this code may require a scan tool to retrieve the code and data related to the reductant system. Basic electrical testing of the heater and related components may also be necessary.

7. Will resetting the check engine light resolve OBDII code P221D?

- Simply resetting the check engine light will not resolve the underlying issue causing code P221D. The root cause of the code should be identified and addressed to prevent it from reoccurring.

8. Is OBDII code P221D specific to certain vehicle makes and models?

- While code P221D is a generic OBDII code related to the reductant system, its specific interpretation and troubleshooting steps may vary slightly depending on the vehicle make and model.

9. Can a DIY enthusiast repair OBDII code P221D, or should it be done by a professional?

- Depending on the individual's skill level and access to tools, a DIY enthusiast may be able to address code P221D by following proper diagnostic procedures and repair guidelines. However, complex electrical issues may require professional assistance.

10. How much does it typically cost to repair OBDII code P221D at a mechanic or dealership?

- The cost of repairing code P221D can vary depending on the root cause of the issue, the labor rates of the mechanic or dealership, and the cost of any parts that need to be replaced. It is advisable to obtain a diagnosis and quote before proceeding with the repairs.