Exhaust aftertreatment fuel injector B internally shorted or stuck open; Chafed or shorted wiring in the injector control circuit contacting ground; Corroded or damaged electrical connector at the injector; Failed driver circuit inside the powertrain control module; Contamination or debris holding the injector pintle open; Exhaust system modifications or leaks that allow moisture into the injector

DTC codes / P20xx · Fuel and air metering and auxiliary emission controls / P20D5

P20D5Exhaust Aftertreatment Fuel Injector B Stuck Open

Q: What does code P20D5 mean?

Exhaust Aftertreatment Fuel Injector B Stuck Open. This code indicates that the powertrain control module has detected a stuck-open condition in the circuit for exhaust aftertreatment fuel injector B, which is used to inject diesel fuel into the exhaust stream to raise temperature for regeneration of the diesel particulate filter. The computer monitors the injector circuit and recognizes that current flow remains higher than expected even when the injector should be closed, signalling a short to ground or a failed injector.

This code indicates that the powertrain control module has detected a stuck-open condition in the circuit for exhaust aftertreatment fuel injector B, which is used to inject diesel fuel into the exhaust stream to raise temperature for regeneration of the diesel particulate filter. The computer monitors the injector circuit and recognizes that current flow remains higher than expected even when the injector should be closed, signalling a short to ground or a failed injector.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaFuel and air metering and auxiliary emission controls

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
A noticeable fuel smell from the exhaust, especially after the engine is shut off
White or bluish smoke from the tailpipe due to unburned fuel entering the exhaust
Reduced fuel economy as extra fuel is injected when it should not be
Possible rough running or misfire if the excess fuel affects exhaust backpressure
In some cases, the vehicle may enter limp mode or limit regeneration events

Common causes, most likely first

Exhaust aftertreatment fuel injector B internally shorted or stuck open
Chafed or shorted wiring in the injector control circuit contacting ground
Corroded or damaged electrical connector at the injector
Failed driver circuit inside the powertrain control module
Contamination or debris holding the injector pintle open
Exhaust system modifications or leaks that allow moisture into the injector

How to diagnose and fix it

Use a scan tool to verify the code and check for related codes in the aftertreatment system
Inspect the injector wiring harness and connector for chafing, corrosion, or loose pins
Measure the resistance of the injector with a multimeter and compare to specifications
Disconnect the injector and check for a short to ground on the control wire
If the circuit tests good, remove and inspect the injector for sticking or contamination
Replace the faulty injector and clear the codes, then perform a regeneration test drive
If the code returns, test the powertrain control module driver circuit or replace the module

Before replacing the exhaust fuel injector

A stuck-open injector often causes no driveability symptoms, so the code may be the only clue and should not be ignored.
Wiring harness damage near the exhaust manifold is a common cause that is frequently overlooked when only the injector is replaced.
Excess fuel from a stuck-open injector can wash down cylinder walls and dilute engine oil, so check oil level and condition.
The code can be set by a short to ground in the control wire even if the injector itself is good, so always test the circuit first.
After repairs, a forced regeneration with a scan tool is often needed to verify the fix and prevent repeat codes.

Can I keep driving with P20D5?

It is not recommended to drive for long with this code because unburned fuel can overheat and damage the diesel particulate filter. If you must drive, avoid heavy loads and long idling, and schedule service as soon as possible.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.