P20D6 Exhaust Aftertreatment Fuel Injector B Stuck Closed

The second exhaust fuel doser (B) fails to deliver fuel even though the control unit commands it open. No manufacturer documents P20D6 publicly. For doser A, Volvo and Mack handle the matching code P20D0 by checking the dosing module and replacing the nozzle, whose tip tends to clog with carbon; the same weak spot applies to B. A blocked doser means the catalyst stays too cool for regeneration, so soot keeps accumulating in the filter until power is cut back. CARB requires a malfunction once the injection system cannot achieve regeneration. Stuck open on the same doser is P20D5.

Likely causes

Symptoms

• Check engine light on
• Failed or frequent regenerations
• Reduced power once the filter is heavily loaded

Repair estimate

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

Related codes

References: law.cornell.edu, static.nhtsa.gov.