Fault code P20D5 – exhaust aftertreatment fuel injector “B” stuck open

Fault code P20D5 is called “Exhaust Aftertreatment Fuel Injector “B” Stuck Open” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P20D5

Stored code P20D5 means that the control module has detected a fuel injector “B” of the exhaust aftertreatment system stuck in the open position. The marked “B” injector indicates which recovery injector has failed.

Fault code P20D5 – exhaust aftertreatment fuel injector

The exhaust aftertreatment system (EAS) is sometimes called a selective catalytic reduction (SCR) system. Typically, the system consists of a catalyst, particulate filter, reducing agent injection system, and nitrogen oxide (NOx) trap.

SCR systems inject a reducing agent into the exhaust before the particulate filter or catalytic converter. Precisely timed injection increases the temperature of the filter element and allows it to work more efficiently.

As a result, the filter element lasts longer and emits less harmful exhaust gases.

The entire SCS system is monitored and controlled either by the PCM or by a separate controller that communicates with the PCM. The controller monitors the O₂, NOx and exhaust temperature sensors to determine the appropriate time to inject the reducing agent.

If the PCM detects an EAS “B” fuel injector stuck in the open position. Then code P20D5 will be stored and the malfunction indicator light may illuminate.

Symptoms of vehicle malfunctions

The main signal that an error P20D5 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. The “Check engine” control lamp on the control panel will light up (the code will be stored as a fault).
  2. Other related fault codes may also be present.
  3. Reduced engine power.
  4. Black smoke coming out of the exhaust pipe.
  5. Increased fuel consumption.
  6. The engine may go into emergency operation.

Stored fault code P20D5 should be considered serious and corrected as soon as possible. The SCR system may be disabled, causing damage to the particulate filter and catalytic converter.

Factors that can cause this error code

The error code P20D5 can mean that one or more of the following problems have occurred:

  • EAS fuel injector is defective.
  • Open or short circuit in exhaust aftertreatment control circuit.
  • Insufficient recovering fluid in the tank.
  • In rare cases, PCM failure or programming error.

How to fix or reset OBD-2 code P20D5

Some suggested steps for troubleshooting and fix the error code P20D5:

  1. Read all stored data and error codes with an OBD-II scan tool. To find out when and under what circumstances error P20D5 appeared.
  2. Clear the error codes from the computer memory and test-drive the vehicle to see if the fault appears again.
  3. If the error code appears again, visually inspect the electrical wires and connectors.
  4. Visually inspect and test the EAS fuel injector.
  5. If necessary, repair or replace the EAS fuel injector and any defective wires.
  6. Check the reconditioning fluid in the tank.
  7. If there are no defects, check the PCM module and its program part.

Diagnose and repair of problems

Before you begin the process of troubleshooting a P20D5, you should research the technical service bulletins (TSBs) for your particular vehicle. In some cases, this can save a lot of time by pointing you in the right direction.

The diagnosis itself should begin with a visual inspection of the restorer system harnesses and connectors. Burned or damaged wiring and connectors should be repaired or replaced before proceeding with testing.

Using a multimeter, test the power supply to the SCR control system. Check the fuses when the circuit is loaded to avoid misdiagnosis.

Using a scan tool, activate the EAS fuel injector to check the control circuit output voltage. If the voltage is insufficient, the controller is most likely defective or has a programming error.

When the voltage output circuit is within the parameters, use a multimeter to check the EAS fuel injector. If the injector does not meet the manufacturer’s specifications, it has most likely failed.

In most cases, failure of the EAS fuel injector is the cause of error P20D5.

On which vehicles does this problem occur most frequently

Fault code P20D5 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Chevrolet
  • Ford
  • GMC
  • Mercedes-Benz (Sprinter)
  • Toyota (Land Cruiser)

Fault code P20D5 can sometimes be found with other errors. The most common are the following: P20D1, P20D2, P20D3, P20D4, P20D6.


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