Failed exhaust aftertreatment fuel injector B (stuck closed internally); Open or shorted wiring in the injector control circuit; Corroded or loose electrical connector at the injector; Faulty powertrain control module driver for the injector circuit; Clogged fuel supply line or low fuel pressure to the injector; Exhaust system blockage or excessive backpressure preventing proper injector operation

DTC codes / P20xx · Fuel and air metering and auxiliary emission controls / P20D6

P20D6Exhaust Aftertreatment Fuel Injector B Stuck Closed

Q: What does code P20D6 mean?

Exhaust Aftertreatment Fuel Injector B Stuck Closed. P20D6 indicates that the powertrain control module has detected a fault in the exhaust aftertreatment fuel injector B circuit, specifically that the injector is stuck closed. The computer commands the injector to open and deliver fuel into the exhaust stream for regeneration or heating, but the circuit feedback or resulting temperature change does not match the expected response.

P20D6 indicates that the powertrain control module has detected a fault in the exhaust aftertreatment fuel injector B circuit, specifically that the injector is stuck closed. The computer commands the injector to open and deliver fuel into the exhaust stream for regeneration or heating, but the circuit feedback or resulting temperature change does not match the expected response.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering and auxiliary emission controls

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Reduced fuel economy due to frequent or failed regeneration attempts
A noticeable decrease in engine power or limp mode in some vehicles
Exhaust smoke or unusual odor if the injector leaks or fails to deliver fuel
Extended crank times or rough running if the fault affects related systems
A message on the driver information center indicating exhaust system service required

Common causes, most likely first

Failed exhaust aftertreatment fuel injector B (stuck closed internally)
Open or shorted wiring in the injector control circuit
Corroded or loose electrical connector at the injector
Faulty powertrain control module driver for the injector circuit
Clogged fuel supply line or low fuel pressure to the injector
Exhaust system blockage or excessive backpressure preventing proper injector operation

How to diagnose and fix it

Inspect the injector electrical connector and wiring for damage, corrosion, or looseness
Measure the resistance of the injector and compare to the manufacturer's specification
Check for battery voltage and ground signals at the injector connector during a commanded activation
Test fuel pressure and flow to the injector to rule out supply issues
Perform a bidirectional scan tool test to command the injector on and observe circuit response
Replace the exhaust aftertreatment fuel injector B if it fails electrical or flow testing
Clear the diagnostic trouble codes and verify the repair with a road test that includes a regeneration cycle

What a stuck-closed injector really means

A stuck-closed injector often sets this code without any driveability complaint, so the warning light may be the only clue until regeneration fails.
Technicians sometimes replace the injector only to find the real fault is a chafed wire in the harness near the exhaust, so always inspect the circuit first.
This code can be set by a fuel pressure problem rather than a failed injector, especially if the low-pressure pump is weak or the filter is restricted.
On some vehicles, the aftertreatment injector is used for both regeneration and exhaust heating, so a stuck-closed injector may cause a secondary code for catalyst efficiency or particulate filter performance.
A scan tool that can command the injector on and off is essential; without it, you cannot confirm whether the injector or the control circuit is at fault.

Can I keep driving with P20D6?

You can usually continue driving to a repair shop, but avoid heavy loads and long trips because the exhaust aftertreatment system may not regenerate properly. If the check engine light starts flashing or you notice severe power loss, stop driving and seek service immediately.

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.