Need car parts? Select your vehicle
Reading Time: 5 minutes

The P20BA is a trouble code that indicates a potential issue with the control circuit of a diesel engine’s reductant heater.

What is a reductant heater and why is it important?

The reductant heater is a component that is used to prevent diesel exhaust fluid from freezing or crystallizing in low temperatures. It is usually located in the diesel exhaust fluid filter reservoir and/or the reductant injector supply hose(s).

What Does the P20BA Code Mean?

Diagnostic trouble code (DTC) P20BA stands for “Reductant Heater “A” Control Circuit Performance.” This trouble code sets when the powertrain control module (PCM) has detected that the voltage signal from the control circuit of the designated reductant heater “A” is out of the expected range. The P20BA trouble code may also be stored if the reductant heater does not perform as required.

The designation of reductant heaters is used in vehicles that have multiple units. In order to determine which is the “A” circuit in your specific application, you will need to consult a specific repair manual or database.

Replacement Diesel Emissions Fluid Heater Isolated
P20BA trouble code may be stored if the reductant heater does not perform as required.

Note: The definition of code P20BA may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition

While modern diesel engines are built to be more powerful than ever, they cannot meet strict federal US emissions standards with basic exhaust management systems (i.e., exhaust gas recirculation or EGR, diesel particulate filters (DPF), catalytic converters, NOx trap). The selective catalytic reduction (SCR) system was invented to better manage the exhaust of strong diesel engines by reducing the amount of leftover NOx in the exhaust system.

The selective catalytic reduction system works by injecting a reductant compound or a diesel exhaust fluid (DEF) into the exhaust. Injecting diesel exhaust fluid in a precisely-timed manner helps elevate and maintain the proper exhaust temperature needed to maximize filtration. This process reduces the amount of harmful exhaust entering the atmosphere.

The PCM or a dedicated SCR controller is responsible for monitoring the entire selective catalytic reduction system. The controller determines the exact timing of diesel exhaust fluid injection by keeping track of the oxygen sensor, NOx sensor, and the exhaust temperature sensor, among others.

The P20BA code is a serious code that should be addressed immediately because it may disable the SCR system. Catalytic converter damage may also occur as a result if this code isn’t urgently addressed.

What Are the Possible Causes of the P20BA Code?

Like many other trouble codes, the P20BA trouble code has several possible causes. Below are some of the most likely reasons why the P20BA code sets:

  • Faulty reductant heater
  • Bad reductant temperature sensor
  • Wiring issues, such as open or shorted circuits in the reductant heater control
  • Glow plug control module (GPCM)/ SCR controller failure
  • Faulty PCM/ programming error (not usually)

What Are the Common Symptoms of the P20BA Code?

When a trouble code sets, the vehicle’s PCM may send a signal to illuminate the appropriate warning light. In some cases, an active warning light is the only indicator that a trouble code has set. However, in many cases, other signs may also be noticeable. Below are the most common symptoms of the P20BA code:

  • Malfunction indicator lamp (MIL) or check engine light on
  • DPF regeneration may not occur (possibly putting the vehicle into Reduced Power Mode)
  • Other SCR-related codes may set

How to Diagnose the P20BA Code

mechanic with blue clothing determines the OBD code with diagnostic scanner
In order to properly diagnose and fix the problem, you’ll have to narrow down the main cause from a list of possible causes.

Diagnostic trouble codes can only indicate the general location and nature of a potential issue within the vehicle, not the root cause. In order to properly diagnose and fix the problem, you’ll have to narrow down the main cause from a list of possible causes. This is a time-consuming task that requires accuracy and attention to detail.

If you want to learn more about the troubleshooting process for the P20BA trouble code, repair manuals and databases are the best sources of information. These resources contain detailed repair information as well as helpful visual guides, such as diagrams and illustrations.

How to Fix the P20BA Code

In order to come up with an effective, long-term solution to a diagnostic trouble code such as P20BA, you’ll  first need to consult a vehicle-specific repair manual or database. These sources provide detailed repair information that’s particular to a specific make and model. Remember that vehicles are made differently, depending on the manufacturer. That means that vehicles will have varying terminology and components.

The same holds true for repair instructions. Let’s compare the setting conditions for the P20BA code on a Ford vehicle (2016 Ford F-250 Super Duty Platinum) and on a GMC vehicle (2015 GMC Sierra 2500HD SLT). The P20BA code sets on a Ford F-250 when the reductant dosage control module determines that the conductance of the reductant heater does not fall within a set threshold.

Meanwhile, the P20BA code on GMC vehicles is stored if specific conditions (i.e., voltage, engine speed, emission reduction fluid tank level, activity duration, and temperature readings, etc.) are met. Because of this, the troubleshooting process and solution to the P20BA code on a Ford vehicle are vastly different from those on a GMC vehicle.

If you’re a seasoned DIYer who’s planning on fixing the P20BA code on your own, a vehicle-specific repair manual or database is your best resource. However, if you’re not familiar with how trouble code repairs work, it’s best to consult a certified mechanic or technician for repairs so you can avoid personal injury or costly mistakes.

Products Mentioned in this Guide

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

husky liners wheel well guards
Notify of
Inline Feedbacks
View all comments
Kevin French

I had a code P20b9 on 2011 3500HD Chevy. I fix the problem but can’t reset code do you know what scanner I can buy that will reset this code without having to take my truck to a dealer

Hi Kevin,

P20B9 is a generic code that any scan tool or code reader should be able to clear. If the code refuses to clear, that’s because the problem has not actually been fixed, and the computer is re-setting the code right away. Usually, this happens when there’s an open circuit that the computer picks up on immediately.

View all Questions & Answers Answers BE PART OF OUR COMMUNITY: Share your knowledge & help fellow drivers Join Now
Copyright ©2022, Inc. All Rights Reserved.