AutoCodes – GMC – P221C GMC

P221C GMC 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 GMC 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 1,212

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

What does this mean?

What are the Possible Causes of the DTC P221C GMC?

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 GMC?

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 GMC 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 GMC code?

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Need Help with the Code?

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

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 GMC Code

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

The common symptoms of code P221C include the check engine light illuminating, reduced engine performance, and potential issues with emissions.

2. What can cause the OBDII code P221C GMC to trigger?

Code P221C is usually triggered by a malfunction in the reductant heater 2 circuit, which can be caused by a faulty heater element, wiring issues, or a defective reductant heater control module.

3. How serious is the OBDII code P221C GMC?

While the severity can vary, it is important to address code P221C promptly to avoid potential damage to the emissions control system and ensure proper vehicle performance.

4. How can I diagnose the OBDII code P221C GMC?

Diagnosing code P221C typically involves using a scan tool to retrieve the code, inspecting the reductant heater 2 system components for damage or corrosion, and testing the circuit for proper voltage and continuity.

5. What are some repair tips for fixing OBDII code P221C GMC?

Repair tips for addressing code P221C may include checking and repairing any damaged wiring, replacing the reductant heater 2 element if faulty, or resetting the code after repairs are completed.

6. Can I drive my vehicle with the OBDII code P221C GMC illuminated?

It is generally not recommended to drive with the check engine light on, as it indicates a potential issue that requires attention. It is best to address code P221C as soon as possible.

7. How much does it cost to repair OBDII code P221C GMC?

The cost of repairing code P221C can vary depending on the cause of the issue, the extent of the repairs needed, and labor rates in your area. It is advisable to consult with a professional mechanic for an accurate estimate.

8. Can I reset the OBDII code P221C GMC on my own?

You can attempt to reset the code using an OBDII scanner or by disconnecting the vehicle's battery for a few minutes. However, it is important to address the underlying issue causing the code to prevent it from reoccurring.

9. Will OBDII code P221C GMC affect my vehicle's fuel efficiency?

Code P221C may impact your vehicle's fuel efficiency if it causes engine performance issues or affects the emissions control system. Addressing the code promptly can help maintain optimal fuel efficiency.

10. How long does it take to repair OBDII code P221C GMC?

The repair time for code P221C can vary depending on the specific cause of the issue, the availability of parts, and the mechanic's expertise. Simple fixes may take a few hours, while more complex repairs could require more time.