SPN 5394
CAUTION
DEF dosing valve
The truck's control module (ECU) reports a fault on: DEF dosing valve.
SPN 5394 means a truck control module (ECU) flagged a fault on DEF dosing valve, part of the SCR / DEF system on heavy-duty diesel trucks. DERATE rates it CAUTION: drive to a shop today, because the engine may cut power. Part usually replaced: DEF dosing valve / injector, $250–$900 (aftermarket to dealer) plus 1–2.5 h labor.
SCR / DEF
Can I keep driving?
Drive to a shop today. The engine may cut power (derate) if the fault stays active.
Part usually replaced
DEF dosing valve / injector
$250–$900 (aftermarket to dealer)
Labor: 1–2.5 h
USD, part only. Labor is billed at the shop's hourly rate.
Data: DERATE verified base, updated October 2026
Related codes
Read it off your own dash
Take one photo and DERATE tells you whether you can keep driving.
Ask DERATE
DERATE assists. It does not replace inspection by a qualified technician.