What it means
Exhaust Aftertreatment Fuel Injector B Control Circuit/Open: the control circuit is open. This injector doses fuel into the exhaust to raise temperature for diesel particulate-filter regeneration; it does not fuel the engine.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Aftertreatment fuel injector B meters fuel into the exhaust to raise temperature for DPF regeneration and is separate from engine fueling. P20D1 sets when injector B’s control circuit is detected open, meaning the electrical path may be broken at the injector winding, connector, wiring, or control module connection.
Common causes
Most likely first.
- Injector winding open
- Pin pushed back out of connector body
- Cracked solder joint inside the module or sensor
Symptoms
- Check engine light on
- Possible exhaust smoke or fuel odor during regeneration
How to diagnose it
- Save freeze-frame data and review injector B command and regeneration status to understand when the open-circuit fault appeared.
- Inspect injector B’s connector for a pushed-back pin, corrosion, looseness, or damaged wiring.
- With the ignition off as directed by the manufacturer, disconnect injector B and check its winding for an open circuit against the manufacturer’s specification.
- Check continuity through injector B’s control wire and inspect the harness for breaks or chafing.
- If the injector and harness pass, check the relevant control-module connector and circuit driver using the manufacturer’s wiring diagram and procedure.
Common fixes
- Seat or replace a pushed-back or damaged terminal at injector B’s connector.
- Repair a broken or chafed section of injector B wiring.
- Replace injector B if its winding is open against the manufacturer’s specification.
- Repair the control-module connection or module fault if testing isolates the open circuit there.
Can I keep driving?
If the vehicle drives normally, a short trip for diagnosis is generally reasonable, but DPF regeneration may be incomplete and soot loading can rise with continued use. Avoid long trips if regeneration warnings or reduced power appear.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.