1921 SPN Fault Code

1921 spn fault code name is Aux Valve 1 Fail Safe Mode Command. If you don't take the time to look into 1921 spn fault when it arises, it can add up quickly. One small issue like 1921 can cause a larger component to become damaged without taking the time to investigate. If you suspect your truck is suffering from one of these issues, look into replacing those small components to save money down the road.

Note: The name and description of 1921 code represents text descriptions for faults supported by another coding system and does not necessarily comply with SAE J1939. For a specific engine manufacturer's explanation for codes, please consult the engine's technical manual. See also other spn codes.