P20DA Exhaust Aftertreatment Fuel Supply Control Circuit High

For the supply valve ahead of the exhaust doser, the control line reads too high, typically because it touches battery voltage or, on some drivers, an open line pulled up internally. Volvo and Mack log it as P20DA00 and list it in guide KC-2157 among the AHI module electrical faults, with the instruction to check that module's wiring and connector. A circuit stuck high leaves the valve unable to follow commands, so the control unit stops dosing and active regeneration is lost until the fault is repaired. Its siblings are P20D7 (line broken) and P20D9 (line grounded); a mechanically stuck valve sets P20DB or P20DC.

Likely causes

Symptoms

• Check engine light on
• Active regeneration not possible

Repair estimate

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

Parts involved

Related codes

References: static.nhtsa.gov, static.nhtsa.gov.