AutoCodes – GMC – P221E GMC

P221E GMC Code - Reductant Heater 3 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 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: P221E GMC indicates Reductant Heater 3 Current Too Low.
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.

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Code Popularity 822

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 P221E 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 P221E GMC - Reductant Heater 3 Current Too Low - AutoCodes.com — P221E GMC Code - Reductant Heater 3 Current Too Low

What does this mean?

What are the Possible Causes of the DTC P221E 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 P221E 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 P221E 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.

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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 P221E GMC Code

1. What are the common symptoms of OBDII code P221E GMC (Reductant Heater 3 Current Too Low)?

The common symptoms include the check engine light coming on, reduced engine performance, and potential failure to pass emissions tests.

2. What are the possible causes of OBDII code P221E GMC?

The code P221E GMC (Reductant Heater 3 Current Too Low) can be caused by issues such as a faulty reductant heater 3, wiring issues, a defective reductant heater control module, or a malfunctioning powertrain control module (PCM).

3. How can I diagnose the cause of OBDII code P221E GMC?

Diagnosing the cause of P221E involves using an OBDII scanner to retrieve the code, checking the reductant heater 3 and related components for faults, and inspecting the wiring for any damage or loose connections.

4. Can I continue driving with OBDII code P221E GMC?

It is generally not recommended to continue driving with the P221E code present, as it can lead to reduced engine performance and potential damage to the emissions control system. It is advisable to address the issue promptly.

5. How can I repair OBDII code P221E GMC?

Repairing P221E involves addressing the root cause of the code, which may involve replacing the faulty reductant heater 3, repairing or replacing damaged wiring, or addressing any issues with the control modules.

6. Is it possible to reset OBDII code P221E GMC without repairs?

While you can clear the code with an OBDII scanner, it is not recommended to do so without addressing the underlying issue causing the P221E code. Ignoring the problem can lead to further complications.

7. Can a DIY enthusiast fix OBDII code P221E GMC?

Depending on your level of experience and access to tools, a DIY enthusiast may be able to address the P221E code by following repair guides, but it is recommended to consult a professional if unsure.

8. How much does it cost to repair OBDII code P221E GMC at a mechanic?

The cost of repairing P221E at a mechanic can vary depending on the root cause of the issue, the cost of parts, and labor rates. It is advisable to get multiple quotes from different mechanics.

9. What other codes may be associated with OBDII code P221E GMC?

Other related codes that may be associated with P221E include P220E (Reductant Heater 3 Control Circuit/Open) and P220F (Reductant Heater 3 Control Circuit Performance).

10. How long does it take to repair OBDII code P221E GMC?

The repair time for P221E can vary depending on the complexity of the issue and the availability of parts. It may take anywhere from a few hours to a day or more to diagnose and fix the problem.