What it means
Exhaust Aftertreatment Fuel Injector A 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
Exhaust aftertreatment fuel injector A sprays fuel into the exhaust to raise its temperature for diesel particulate filter regeneration; it does not supply fuel to the engine. The control module monitors injector A’s electrical path and sets P20CB when that circuit is open and current cannot flow as expected.
Common causes
Most likely first.
- Injector winding open
- Open wire to injector
- Pin pushed back out of connector body
Symptoms
- Check engine light on
- Possible exhaust smoke or fuel odor during regeneration
How to diagnose it
- Review freeze-frame data and DPF regeneration status, and check for related aftertreatment injector or circuit codes.
- With the exhaust cool and the system powered down as directed by the manufacturer, inspect injector A’s connector and harness for a loose plug, broken wire, corrosion, or a backed-out pin.
- Check connector seating and terminal retention, then inspect the harness route for heat damage or abrasion near the exhaust.
- Test injector A’s winding and circuit continuity using the wiring diagram and the manufacturer’s procedure to locate the open.
- If the injector and wiring pass, check the control-module side of the circuit against the manufacturer’s specification.
Common fixes
- Reseat a loose injector A connector and secure its terminals.
- Repair an open or heat-damaged wire in injector A’s circuit.
- Replace injector A if its winding is confirmed open.
- Repair the module-side circuit only if testing confirms that it is the source of the open.
Can I keep driving?
The engine may still run normally, but DPF regeneration can be impaired and the filter may accumulate soot. Avoid repeatedly interrupting regeneration attempts, and have the fault addressed if DPF warnings appear or exhaust smoke or fuel odor occurs during regeneration.
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.