What are the most likely causes of SPN 94?

Plugged fuel filter; Weak transfer pump; Air in fuel

How do you diagnose code SPN 94?

1) Fuel pressure test at rail with gauge

What part is usually replaced for SPN 94 and how much does it cost?

Fuel filter (primary + secondary): $40–$160 USD (aftermarket to dealer), plus 0.5–1 h of labor.

← All codes

SPN 94

CAUTION

Fuel delivery pressure

The truck's control module (ECU) reports a fault on: Fuel delivery pressure.

SPN 94 means a truck control module (ECU) flagged a fault on fuel delivery pressure, part of the Fuel system on heavy-duty diesel trucks. DERATE rates it CAUTION: drive to a shop today, because the engine may cut power. Part usually replaced: Fuel filter (primary + secondary), $40–$160 (aftermarket to dealer) plus 0.5–1 h labor.

Fuel

Can I keep driving?

Drive to a shop today. The engine may cut power (derate) if the fault stays active.

Most likely causes

Plugged fuel filter
Weak transfer pump
Air in fuel

Recommended tests

1. Fuel pressure test at rail with gauge

Part usually replaced

Fuel filter (primary + secondary)

$40–$160 (aftermarket to dealer)

Labor: 0.5–1 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.

Available on the

App Store

Get it on

Google Play

Coming soon

Discover DERATE

Ask DERATE

Print your glovebox rescue cardThe most common codes, how urgent each one is and what to tell the mechanic, on one sheet.

DERATE assists. It does not replace inspection by a qualified technician.