P20B9 Code 6.7 Powerstroke: What Does it Mean?, Causes, Symptoms & Fixes

The P20B9 diagnostic trouble code (DTC) has been common to many diesel engine vehicles since 1996. But the P20B9 code 6.7 Powerstroke has gained high notoriety due to its frequent occurrence and confusing source issues.

According to the code’s definition, P20B9 means that the control circuit of reductant heater A is open or unresponsive. Typically, the appearance of P20B9 indicates some fault in the DEF tank, DEF/reductant heater, or PCM.

Although this code is often the result of exhaust system problems, other critical and underlying problems can also be the cause. So, ignoring and not fixing the code would be a bad decision.

In this article, I’ll explain all the components and faults associated with this code, alongside the common symptoms and fixes.

What Does P20B9 Code Means in 6.7 Powerstroke Diesel?

As I stated earlier, this code says, “Reductant Heater ‘A’ Control Circuit/Open,” where A indicates the specific heater in the diesel exhaust fluid (DEF) tank.

The SCR system in 6.7 Powerstroke requires a reductant component: the DEF. This urea and deionized water solution is injected into the exhaust stream to react with NOx emissions and neutralize them.

If you live in cold places, DEF freezing will be a common occurrence. DEF freezes at 12o F (-11o C), and when the reductant temperature sensor detects that the DEF’s temperature is approaching freezing point, the PCM (power control module) instructs the glow plug control module to provide power to the heating element.

The OBD scanner reading the P20B9 code means the PCM has picked up no voltage from the DEF tank reductant heater. In other words, the operation of PCM trying to launch the DEF heater has failed for some reason.

This usually means that the heater is malfunctioning or the PCM has some sort of issue. Besides these, the issue can also stem from the wiring, sensors, and connectors associated with the heater circuit.

Also Read: Ford 6.7 Powerstroke DPF Back Exhaust Worth It?

Is the P20B9 Code Serious in 6.7 Engine?

On the surface, the code seems pretty generic. But that’s not the case in reality. As the manufacturers and the government highly mandate the SCR system, its well-being is engineered to be highly integrated into your engine performance.

You have read this DTC in the scanner means the SCR system is most probably not working. And a diesel truck with disabled SCR is not passing the emission test ever, which means your vehicle is no longer on-roadworthy.

Besides the emission quality being severely poor, your engine will suffer from performance issues and poor fuel economy. The SCR system will also be subjected to catalyst damage which refers to the degradation of the SCR catalyst.

So, it is important to address the P20B9 code as promptly as possible to avoid these problems from the 6.7 engine.

Another Diagnostic Trouble Code for 6.7 Powerstroke Engine: P1249 Code 6.7 Powerstroke.

6 Common Symptoms Indicating a P20B9 Code in Powerstroke 6.7

Like other DTCs, P20B9 comes with some common signs for you to identify. As soon as you notice your vehicle showing 2 or 3 of the signs mentioned below, get a proper scan.

1. Dwindling Engine Performance

This is a common sign for most of the issues with your engine. Whenever you notice reduced engine performance, engine hesitation, or a noticeable decrease in acceleration, check for potential error codes.

2. Poor Fuel Economy

A faulty reductant heater can impact your 6.7 Powerstroke’s fuel mileage. If you notice a sudden decrease in fuel economy or find that you need to refuel more frequently than usual, it could be related to the P20B9 code.

3. Illuminated Check Engine Light

This is another common symptom of P20B9. The CEL indicates that the engine/power control module (ECM) has detected a fault and has stored a diagnostic trouble code (DTC), in this case, P20B9.

4. Failed Emissions Test

As the P20B9 code means that the SCR process is not running properly, the engine emission will contain a high amount of NOx content. So, there is no chance your vehicle is passing an emission test. 

5. Excessive Amount of Black Smoke

Due to the reduction reaction not taking place in the SCR, the emission quality will be very poor and full of black smoke. 

6. Other Related Codes

In many cases, the P20B9 code will be accompanied by other codes related to the reductant system or emissions control, like P20BA And P20BB.

Reasons Behind P20B9 DTC in 6.7 Powerstroke

There can be quite a few potential causes of the P20B9 code. Some of the most common ones are –

● Faulty Reductant Heater

Any critical mechanical damage or electrical fault in the heater circuit and parts can make the heater malfunction.

● Wiring or Connection Issues

With damaged wiring or loose connection, the PCM won’t be able to communicate and run processes with the heater components and sensors.

● Faulty PCM

PCM is like the brain of the engine, constantly regulating and controlling various engine processes. A faulty PCM may fail to communicate with the heater and control it, thus printing the code.

● Malfunctioning Reductant Heater Sensor

The heating mechanism has a sensor for detecting when the DEF temperature seems lower than normal or close to freezing. If the sensor is not working, the PCM won’t know the DEF condition and will fail to start the heater when required.

● Dirty DEF Tank

The heater struggling to heat the DEF properly or pick up the correct temperature of the fluid due to accumulated dirt inside the tank is a common reason for triggering the P20B9 code.

P20B9 Troubleshooting: Tools and Process

For troubleshooting the code, first, you’ll need to manage some tools. Here is the list –

  • An OBD-II scanner
  • A digital multimeter (volt/ohmmeter)
  • Wrench set
  • Flashlight
  • Source of diagnostic information
  • Other safety gears

1. Check the Wiring Harness and Connections

Looking for damage in the harness or loose wire connections in the reductant heater system should be your first task. It’s because a bad connection will be the most apparent cause of this code, and you can avoid a lot of hassle regarding the diagnosis process if you find the issue here.

To ensure that the wiring harness is actually working, use the multimeter or volt/ohmmeter to read the voltage differences and match the values with a technical service bulletin.

Make sure the bulletin is specific to your vehicle model and year.

2. Scan the Codes

If there is no issue found with the reductant heater harness and connectors, connect the OBD scanner with the PCM to get the specific error codes. Reading the P20B9 code will need you to do the next steps.

3. Inspect the Control System

Check the power supply to the SCR control system by utilizing the multimeter. Ensure that the circuit is loaded before testing the fuses to prevent incorrect diagnosis.

If the power (voltage) values match and the ground circuits required are identified, employ a scanner to activate the reductant heater and assess the voltage of the output control circuit.

This voltage value of the control circuit falling short indicates a faulty controller or potential programming error in the PCM as the cause.

4. Inspect the Heater and DEF Tank

The controller circuit providing optimum value means the issue is probably lying in the heater. Use the multimeter to read and match the voltage output from the heater for mismatched values.

Also, inspect the DEF tank for damage and dirt. Sometimes the heater may be functional, but the heat transfer could be obstructed by something.

Clearing the P20B9 Code

You can do the following steps to get rid of the P20B9 code –

  1. Clean the DEF Tank if dirty.
  2. Fix all the damaged connections or replace the harness.
  3. Replace the DEF heater if it’s faulty.
  4. If the tank is damaged or deformed, replace it.
  5. Replace the PCM if it’s faulty.

Cost of Troubleshooting for P20B9 Code in 6.7 Powerstroke Engine

Problem/StepRequired PartsParts Cost
TroubleshootingComplete tool set$150
Damaged harness or loose connectionWiring Harness$100
Problematic heaterDEF Reservoir Heater $150 – 200
Damaged or too dirty tankDEF Tank$400 – 450
Faulty PCMPCM$800 – 1,100

For 6.7 Powerstroke Owner: Symptoms of Ford 6.7 Powerstroke Turbo Failure.


Can I continue driving with the P20B9 code in a 6.7 Powerstroke?

It is generally not recommended to drive with an active fault code. In this case, it’s most probably about the reductant heater, which plays a crucial role in the vehicle’s exhaust after-treatment system, and driving with a malfunctioning heater can lead to reduced performance and potentially cause further damage.

Why is the scanner reading the P20B9 code in the warm seasons?

In such cases, it’s clearly a programming error in the PCM, and errors in PCM are always highly threatening. So, you should get that PCM checked and repaired as soon as possible.

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