AutoCodes – GMC – P221F GMC

P221F GMC Code - Reductant Heater 3 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 3, Reductant Heater 3 harness is open or shorted, Reductant Heater 3 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: P221F GMC indicates Reductant Heater 3 Current Too High.
Common causes: Common causes include Faulty Reductant Heater 3, Reductant Heater 3 harness is open or shorted, Reductant Heater 3 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.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 459

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 Sep 10, 2021

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

Code P221F 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 short circuit by detecting a high current in the heater.

OBDII Code P221F GMC - Reductant Heater 3 Current Too High - AutoCodes.com — P221F GMC Code - Reductant Heater 3 Current Too High

What does this mean?

What are the Possible Causes of the DTC P221F GMC?

Faulty Reductant Heater 3
Reductant Heater 3 harness is open or shorted
Reductant Heater 3 circuit poor electrical connection
Faulty Glow Plug Control Module (GPCM)

How to Fix the DTC P221F 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 P221F 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 P221F GMC code?

Need more information on how to fix the P221F GMC code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P221F 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 P221F GMC Code

1. What are the common symptoms of OBDII code P221F GMC (Reductant Heater 3 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 are the possible causes of OBDII code P221F GMC?

- The code P221F GMC can be triggered by issues such as a faulty reductant heater, damaged wiring or connectors, or problems with the electronic control module.

3. How can I diagnose the cause of OBDII code P221F GMC?

- To diagnose the cause of this code, you may need to conduct a thorough inspection of the reductant heater system, check the wiring and connectors for any damage, and use a scan tool to gather more information from the vehicle's computer.

4. Can I continue driving my vehicle with OBDII code P221F GMC?

- It is not recommended to continue driving the vehicle with this code present, as it can lead to further damage to the emissions system and potentially cause the vehicle to fail an emissions test.

5. How can I repair OBDII code P221F GMC (Reductant Heater 3 Current Too High)?

- Repairing this code may involve replacing the faulty reductant heater, repairing any damaged wiring or connectors, or reprogramming the electronic control module.

6. Are there any DIY tips for fixing OBDII code P221F GMC?

- While some basic inspections and checks can be done by DIY enthusiasts, it is recommended to seek the help of a professional mechanic for accurate diagnosis and repair of this code.

7. Can a faulty reductant heater cause other issues in the vehicle?

- Yes, a faulty reductant heater can lead to reduced fuel efficiency, increased emissions, and potential damage to other components of the emissions system.

8. How long does it typically take to repair OBDII code P221F GMC?

- The repair time for this code can vary depending on the exact cause of the issue and the availability of parts. It is best to consult with a mechanic for a more accurate estimate.

9. Will resetting the check engine light resolve OBDII code P221F GMC?

- Simply resetting the check engine light will not fix the underlying issue causing the code. It is important to diagnose and repair the root cause to prevent the code from reoccurring.

10. Is OBDII code P221F GMC a common issue in GMC vehicles?

- While not extremely common, the code P221F GMC can occur in GMC vehicles equipped with reductant heater systems, especially in older models or those with high mileage.