AutoCodes – GMC – P20BB 2016 GMC Sierra

P20BB 2016 GMC Sierra Code - Reductant Heater 1 Control Circuit Low 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: P20BB 2016 GMC Sierra indicates Reductant Heater 1 Control Circuit Low 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 162

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 P20BB 2016 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 shorted to ground or overloaded for greater than 4 s.

OBDII Code P20BB 2016 GMC Sierra - Reductant Heater 1 Control Circuit Low Voltage - AutoCodes.com — P20BB 2016 GMC Sierra Code - Reductant Heater 1 Control Circuit Low Voltage

What does this mean?

What are the Possible Causes of the DTC P20BB 2016 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 P20BB 2016 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 P20BB 2016 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 P20BB 2016 GMC Sierra code?

Need more information on how to fix the P20BB 2016 GMC Sierra code? Get Access to Factory Service Manuals

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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 P20BB 2016 GMC Sierra Code

1. What does the OBDII code P20BB mean for a 2016 GMC Sierra?

P20BB indicates a problem with the Reductant Heater 1 Control Circuit, specifically low voltage, which affects the functioning of the diesel exhaust fluid (DEF) system.

2. What are the symptoms of code P20BB in a 2016 GMC Sierra?

Common symptoms include a check engine light, possible reduction in DEF system efficiency, and in some cases, limited engine performance due to emissions system issues.

3. What causes the P20BB code on a GMC Sierra?

Causes may include a faulty reductant heater, damaged wiring or connectors in the control circuit, or a malfunctioning powertrain control module (PCM).

4. Is it safe to drive a 2016 GMC Sierra with code P20BB?

While the truck may still be drivable, ignoring this code could lead to reduced emissions system performance and eventually trigger limp mode, restricting power.

5. How do you diagnose the P20BB code on a 2016 GMC Sierra?

Diagnosis involves inspecting the reductant heater, checking the wiring and connectors for damage, and testing the circuit for proper voltage and continuity.

6. Can a faulty reductant heater cause code P20BB?

Yes, a defective reductant heater can lead to low voltage in the control circuit, triggering the P20BB code.

7. How is the P20BB code repaired on a 2016 GMC Sierra?

Repairs may include replacing the reductant heater, repairing or replacing damaged wiring, or reprogramming or replacing the PCM if needed.

8. What tools are needed to fix code P20BB on a GMC Sierra?

Youâ€™ll need an OBDII scanner, a multimeter to test voltage and continuity, and possibly replacement parts like a reductant heater or wiring harness.

9. Does the P20BB code affect emissions on a 2016 GMC Sierra?

Yes, this code can impact the DEF system, potentially increasing emissions and reducing compliance with environmental regulations.

10. How much does it cost to fix code P20BB on a GMC Sierra?

Repair costs vary but typically range from $200 to $600, depending on whether the reductant heater or wiring needs replacement. Labor costs may increase if extensive diagnostics are required.