AutoCodes – GMC – P20B9 2017 GMC Sierra

P20B9 2017 GMC Sierra Code - Reductant Heater 1 Control Circuit

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: P20B9 2017 GMC Sierra indicates Reductant Heater 1 Control Circuit.
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 293

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 P20B9 2017 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 tank heater control circuit is open for greater than 4 s.

OBDII Code P20B9 2017 GMC Sierra - Reductant Heater 1 Control Circuit - AutoCodes.com — P20B9 2017 GMC Sierra Code - Reductant Heater 1 Control Circuit

What does this mean?

What are the Possible Causes of the DTC P20B9 2017 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 P20B9 2017 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 P20B9 2017 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 P20B9 2017 GMC Sierra code?

Need more information on how to fix the P20B9 2017 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the 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 P20B9 2017 GMC Sierra Code

What does the OBDII code P20B9 mean on a 2017 GMC Sierra?

The P20B9 code indicates an issue with the Reductant Heater 1 Control Circuit, which is responsible for warming the DEF (Diesel Exhaust Fluid) to prevent freezing and ensure proper operation of the emissions system.

What are the common symptoms of a P20B9 code on a 2017 GMC Sierra?

Symptoms may include a check engine light, reduced engine power, poor emissions performance, and possible DEF system warnings on the dashboard.

What causes the P20B9 code to appear?

Common causes include a faulty reductant heater, damaged wiring or connectors in the heater circuit, a blown fuse, or issues with the powertrain control module (PCM).

Can I still drive my 2017 GMC Sierra with a P20B9 code?

While the truck may still be drivable, ignoring the issue can lead to reduced emissions performance, potential DEF system freezing, and eventually, restricted engine function.

How is the P20B9 code diagnosed?

A mechanic will use a scan tool to confirm the code, inspect the reductant heater and its wiring, test the circuit for continuity, and check for power and ground at the heater connector.

What is the most common fix for the P20B9 code?

The most common fix is replacing the faulty reductant heater, though repairing damaged wiring or replacing a blown fuse may also resolve the issue.

How much does it cost to fix the P20B9 code on a GMC Sierra?

Repair costs can range from $150 to $500 or more, depending on whether the issue is with the reductant heater itself, the wiring, or other related components.

Can a blown fuse cause the P20B9 code?

Yes, a blown fuse in the reductant heater circuit can trigger the P20B9 code, as it prevents power from reaching the heater.

Is the P20B9 code covered under warranty for a 2017 GMC Sierra?

It depends on the warranty coverage and mileage of your vehicle. The reductant heater may be covered under the emissions warranty, so check with your dealer.

Can I reset the P20B9 code without repairing the issue?

You can clear the code with an OBDII scanner, but if the underlying issue isn’t fixed, the code will likely return and may cause further problems.