Fix Library
Practical, step-by-step fixes for heavy-duty vehicles & fleet problems — 67 published so far.
A P20EE code means your selective catalytic reduction (SCR) system detects inefficient NOx conversion, usually from contaminated diesel exhaust fluid (DEF), a…
See the fixCold temperatures reduce battery efficiency and increase heating demand, cutting an electric delivery van's range by 20‑40%. Precondition the battery while plugged…
See the fixSudden 20% fuel economy drop usually means a clogged DPF filter, leaking fuel injector, faulty turbo actuator, or incorrect ECM calibration. Start…
See the fixA sudden drop in fuel mileage usually means a clogged fuel filter, faulty injectors, low tire pressure, or a malfunctioning EGR system.…
See the fixHigher DEF consumption usually means the selective catalytic reduction (SCR) system is dosing more fluid to meet NOx limits, often due to…
See the fixA sudden 20% fuel economy drop usually means a clogged DPF, leaking injector, low tire pressure, or a stuck-open EGR valve —…
See the fixA heavy-duty truck alternator stops charging when the voltage regulator fails, the serpentine belt slips, or battery cables are corroded, preventing the…
See the fixYour heavy-duty truck's alternator isn't charging because of worn brushes, a failed voltage regulator, loose or corroded battery cables, a broken drive…
See the fixA DEF system fault with engine derate usually means the aftertreatment system detected a problem — like low DEF fluid, a bad…
See the fixYour DPF regenerates every 50 miles because excessive soot accumulates too fast, usually from short trips, bad injectors, wrong oil, EGR issues,…
See the fixFrequent DPF regeneration usually means the filter is clogged with soot from short trips, bad fuel, or a faulty sensor, preventing passive…
See the fixYour heavy-duty truck's batteries likely won't hold a charge overnight because of parasitic draws from accessories, a failing alternator, sulfated batteries, or…
See the fix
