AutoCodes – GMC – P20C0 2018 GMC Sierra

P20C0 2018 GMC Sierra Code - Reductant Heater 2 Control Circuit High Voltage

Quick Answer

As reductant will freeze at temperatures below -11°C (12°F), there are 2 reductant heaters located in the reductant tank. Common causes include Faulty Reductant Heater, Reductant Heater harness is open or shorted, Reductant Heater 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: P20C0 2018 GMC Sierra indicates Reductant Heater 2 Control Circuit High Voltage.
Common causes: Common causes include Faulty Reductant Heater, Reductant Heater harness is open or shorted, Reductant Heater 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 161

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 Jul 29, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P20C0 2018 GMC Sierra Description

As reductant will freeze at temperatures below -11°C (12°F), there are 2 reductant heaters located in the reductant tank. One heats the reductant in the tank, and one heats the reductant supplied to the reductant injector supply pipe. The Engine Control Module (ECM) monitors the reductant temperature in the tank in order to determine if the reductant temperature is below its freeze point. If the ECM determines that the reductant may be frozen, it activates a "defrost strategy" energizing the reductant eater. This energizing action terminates when the temperature sensor measures a threshold value over which the heater must be deactivated.
The Diagnostic Trouble Code (DTC) will be set when the ECM indicates the reductant line heater control circuit is shorted to a voltage for greater than 4 s.

OBDII Code P20C0 2018 GMC Sierra - Reductant Heater 2 Control Circuit High Voltage - AutoCodes.com — P20C0 2018 GMC Sierra Code - Reductant Heater 2 Control Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P20C0 2018 GMC Sierra?

Faulty Reductant Heater
Reductant Heater harness is open or shorted
Reductant Heater circuit poor electrical connection
Faulty Reductant Pump and Sensor Assembly
Faulty Reductant Control Module

How to Fix the DTC P20C0 2018 GMC Sierra?

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 P20C0 2018 GMC Sierra 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 P20C0 2018 GMC Sierra code?

Need more information on how to fix the P20C0 2018 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P20C0 2018 GMC Sierra 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 P20C0 2018 GMC Sierra Code

What does OBDII code P20C0 mean for a 2018 GMC Sierra?

Code P20C0 indicates a high voltage issue in the Reductant Heater 2 Control Circuit, which is part of the diesel exhaust fluid (DEF) system.

What are common symptoms of code P20C0 in a 2018 GMC Sierra?

Symptoms may include the check engine light turning on, DEF system warnings, reduced engine power, and difficulty maintaining proper DEF temperature.

What causes code P20C0 in a 2018 GMC Sierra?

Common causes include a faulty reductant heater, damaged wiring or connectors in the circuit, or a malfunctioning control module.

Can code P20C0 affect vehicle performance?

Yes, this code can lead to reduced engine performance and prevent the DEF system from functioning properly, potentially causing emissions issues.

How is code P20C0 diagnosed in a 2018 GMC Sierra?

Technicians typically use a scan tool to check for related codes, inspect the wiring and connectors, and test the reductant heater's electrical resistance and voltage.

Can I still drive my 2018 GMC Sierra with code P20C0?

Driving with this code is possible but not recommended, as it may lead to reduced engine performance and increased emissions over time.

How do you fix code P20C0 in a 2018 GMC Sierra?

Repairs may involve replacing the reductant heater, repairing damaged wiring or connectors, or reprogramming the control module if necessary.

How much does it cost to repair code P20C0?

Repair costs can vary widely, but replacing the reductant heater typically costs between $200 and $500, depending on parts and labor.

Can weather conditions cause code P20C0?

Cold weather can sometimes exacerbate issues with the reductant heater, especially if the DEF system struggles to maintain proper temperature.

Is code P20C0 a common issue in GMC Sierra trucks?

Itâ€™s not uncommon for diesel trucks like the GMC Sierra to experience reductant heater-related codes, especially in colder climates or as the vehicle ages.