Code families
P codes relate primarily to powertrain systems, C to chassis, B to body and U to network communication. The first digits also indicate whether a code is broadly standardized or manufacturer-specific.
Manufacturer aliases
Some manufacturers display internal references such as DF codes alongside or instead of an OBD P code. AllChip’s library links supplied aliases to canonical references when a mapping is available.
Context makes the diagnosis
Freeze-frame data, occurrence count, status, ambient condition and related codes matter. A low-voltage event can create many secondary codes; an airflow fault can trigger EGR or boost plausibility codes without the named component being defective.
Before a calibration request
Record every code, repair history and relevant live data. Do not erase evidence before diagnosis. Emissions or safety faults must be repaired and handled in accordance with local law.