AutoCodes – GMC – P221D GMC

P221D GMC 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 GMC 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 247

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

What does this mean?

What are the Possible Causes of the DTC P221D 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 P221D 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 P221D 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 P221D GMC code?

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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 P221D GMC Code

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

- Common symptoms include the check engine light coming on, reduced engine performance, and potential emissions issues.

2. What can cause OBDII code P221D GMC to trigger?

- The code can be triggered by a faulty reductant heater 2, issues with the reductant system, or wiring problems.

3. How serious is OBDII code P221D GMC?

- While the code itself may not cause immediate harm to the vehicle, it can affect emissions and overall engine performance if left unresolved.

4. How can I diagnose the cause of OBDII code P221D GMC?

- Diagnosing the code usually involves checking the reductant heater 2 for proper operation, inspecting the reductant system components, and testing the wiring for any faults.

5. What are some tips for repairing OBDII code P221D GMC?

- Repair tips may include replacing the faulty reductant heater 2, repairing or replacing damaged wiring, and ensuring proper functioning of the reductant system components.

6. Can I drive my vehicle with OBDII code P221D GMC active?

- It is generally not recommended to drive the vehicle with the code active, as it can lead to reduced engine performance and potential emissions issues.

7. How much does it typically cost to repair OBDII code P221D GMC?

- Repair costs can vary depending on the exact cause of the code, but they may range from a few hundred to a few thousand dollars, including parts and labor.

8. Will OBDII code P221D GMC cause my vehicle to fail an emissions test?

- Yes, having this code active may cause your vehicle to fail an emissions test due to potential issues with the reductant system.

9. Can I reset OBDII code P221D GMC with a simple OBDII scanner?

- While you can clear the code with an OBDII scanner, it is important to diagnose and repair the underlying issue to prevent the code from reoccurring.

10. How long does it typically take to repair OBDII code P221D GMC?

- The repair time can vary depending on the exact cause of the code and the availability of parts, but it may take a few hours to a day for the repair to be completed.