P20D5 Exhaust Aftertreatment Fuel Injector B Stuck Open

The second exhaust fuel doser (B) keeps passing fuel after it has been told to shut. No manufacturer documents P20D5 publicly; for the single doser A, Volvo and Mack trace the equivalent code P20CF to the fuel supply or the dosing module, and Ram fixed it on Cummins pickups with software. Detection usually relies on pressure in the doser feed line not rising again after closing, or on unexplained heat across the catalyst. Raw diesel in a hot catalyst can overheat it and causes smoke and fuel smell. CARB requires such injection faults to be caught. The stuck-closed counterpart is P20D6.

Likely causes

Symptoms

• Check engine light on
• White smoke or fuel smell
• Higher fuel consumption

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.