AutoCodes – Generic – P221C

P221C Code - Reductant Heater 2 Current Too Low

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: P221C indicates Reductant Heater 2 Current Too Low.
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 3,635

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 P221C 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 open circuit by detecting a low current in the heater.

OBDII Code P221C - Reductant Heater 2 Current Too Low - AutoCodes.com — P221C Code - Reductant Heater 2 Current Too Low

What does this mean?

What are the Possible Causes of the DTC P221C?

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 P221C?

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 P221C 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 P221C code?

Need more information on how to fix the P221C code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P221C code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

P221C Chevrolet — Reductant Heater 2 Current Too Low
P221C GMC — Reductant Heater 2 Current Too Low

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 P221C Code

1. What are the common symptoms of OBDII code P221C (Reductant Heater 2 Current Too Low)?

The common symptoms include the malfunction indicator light (MIL) illuminating on the dashboard, reduced engine performance, and potential failure to pass emissions testing.

2. What are the possible causes of OBDII code P221C?

Possible causes of code P221C include a faulty reductant heater 2, damaged wiring or connectors in the reductant heater circuit, a failed powertrain control module (PCM), or issues with the reductant heater control module.

3. How can I diagnose OBDII code P221C?

Diagnosing code P221C involves using a scan tool to retrieve the code, checking for related codes, inspecting the reductant heater 2 and its wiring, testing the heater resistance, and verifying proper operation of the reductant heater system.

4. Can I still drive my vehicle with OBDII code P221C?

It is generally safe to drive the vehicle with code P221C, but it is important to address the issue promptly to prevent potential damage to the emissions system and ensure optimal engine performance.

5. How can I repair OBDII code P221C?

Repairing code P221C may involve replacing the faulty reductant heater 2, repairing damaged wiring or connectors, resetting the PCM, or addressing any underlying issues that may have triggered the code.

6. Is it possible to reset OBDII code P221C without fixing the underlying issue?

Resetting the code without addressing the underlying issue may temporarily turn off the MIL, but the code is likely to return if the root cause of the problem is not resolved.

7. Can a DIY enthusiast fix OBDII code P221C at home?

Depending on the skill level and experience of the individual, some DIY enthusiasts may be able to diagnose and repair code P221C at home. However, complex electrical issues may require professional assistance.

8. How much does it typically cost to repair OBDII code P221C?

The cost of repairing code P221C can vary depending on the specific cause of the issue, parts needed for replacement, and labor costs. On average, the repair may range from $100 to $500 or more.

9. What are the long-term effects of ignoring OBDII code P221C?

Ignoring code P221C can lead to decreased fuel efficiency, potential damage to the catalytic converter, and increased emissions output. It is advisable to address the issue promptly to avoid more costly repairs in the future.

10. How can I prevent OBDII code P221C from reoccurring?

To prevent code P221C from reoccurring, it is essential to address any underlying issues promptly, follow recommended maintenance schedules, use quality diesel exhaust fluid (DEF), and ensure the reductant heater system is functioning correctly.