Battery voltage low
The reading is real and it is dangerously low. Low oil pressure, low coolant level and low rail pressure land here. Treat it as a real condition until proven otherwise.
SPN 168 — Battery voltage low
SPN 168 is the parameter the ECM is flagging on All makes engines. The FMI that comes with it tells you how it failed. Each failure mode below has its own causes and its own test order — do not treat them as the same repair.
The reference is free. The diagnosis is Pro.
Every SPN and FMI page on this site stays open — no account needed. Pro members can take the code into Blue Collar AI with the VIN, symptoms and photos, keep per-truck history, and print a work order. $14.99 a month or $99.99 a year.