AutoCodes – Generic – P20B9

P20B9 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 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.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 47,901

How popular is this code, among other codes? Medium

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
Tech Notes ▶
Cost to Diagnose
Comments
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

Code P20B9 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 - Reductant Heater 1 Control Circuit - AutoCodes.com — P20B9 Code - Reductant Heater 1 Control Circuit

What does this mean?

What are the Possible Causes of the DTC P20B9?

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?

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 does this mean?

Code Tech Notes

User Submitted Video

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P20B9 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 code?

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

Need Help with the Code?

Get the P20B9 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

P20B9 Chevrolet — Reductant Heater 1 Control Circuit
P20B9 Dodge — Reductant Heater 'A' Control Circuit Open
P20B9 Ford — Reductant Heater 'A' Control Circuit/Open
P20B9 GMC — Reductant Heater 1 Control Circuit
P20B9 Mercedes-Benz — Reductant Heater 'A' Control Circuit/Open
P20B9 RAM — Reductant Heater 'A' Control Circuit Open

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.