Fault Family System: Powertrain (P-Codes) 6 SAE Codes

Exhaust Aftertreatment Fuel Supply Control

Diagnostic & Technical Explanation

P20D7 (Exhaust Aftertreatment Fuel Supply Control Circuit/Open) covers the diesel fuel dosing injector that meters extra fuel directly into the exhaust stream ahead of the oxidation catalyst to raise exhaust temperature for particulate filter regeneration. The ECM distinguishes an open/shorted driver circuit, a performance fault where commanded dosing does not raise exhaust temperature as expected, and a valve mechanically stuck open (which risks catalyst overheating) or stuck closed (which prevents regeneration entirely).

These 6 diagnostic trouble codes share one detection mechanism and one repair path, which is why MechanicDB groups them into a single authored fault family rather than repeating the same explanation 6 times.

Codes in this family (6)

Code	Definition	Repair coverage
P20D7	Exhaust Aftertreatment Fuel Supply Control Circuit/Open	4 ranked fixes
P20D8	Exhaust Aftertreatment Fuel Supply Control Performance	4 ranked fixes
P20D9	Exhaust Aftertreatment Fuel Supply Control Circuit Low	4 ranked fixes
P20DA	Exhaust Aftertreatment Fuel Supply Control Circuit High	4 ranked fixes
P20DB	Exhaust Aftertreatment Fuel Supply Control Stuck Open	4 ranked fixes
P20DC	Exhaust Aftertreatment Fuel Supply Control Stuck Closed	4 ranked fixes

What this page does not show

This page publishes the fault mechanism and the code index. The licensed dataset adds, for every one of the 15,886 codes, the full authored repair set (56,729 procedures in total) with the fields deliberately withheld here:

Procedures 2..n after the first-listed procedure
Aftermarket parts cost ranges in USD (est_parts_cost_min/max_usd)
Professional labor-hour estimates (est_labor_hours)
Step-by-step diagnostic and repair instructions
Replacement-part mappings and catalog lookups
6,637 manufacturer-specific OEM codes across 32 makes ($149 tier)

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