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SPN 641

CAUTION

Turbo actuator (VGT)

The truck's control module (ECU) reports a fault on: Turbo actuator (VGT).

SPN 641 means a truck control module (ECU) flagged a fault on turbo actuator (VGT), part of the Air intake / Turbo system on heavy-duty diesel trucks. DERATE rates it CAUTION: drive to a shop today, because the engine may cut power. Part usually replaced: Turbo (VGT) actuator, $600–$2,200 (aftermarket to dealer) plus 2–5 h labor.

Air intake / Turbo

Can I keep driving?

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

Most likely causes

  • Seized VGT vanes

  • Actuator motor

  • Soot buildup

Recommended tests

  1. 1. Actuator sweep test with software

Part usually replaced

Turbo (VGT) actuator

$600–$2,200 (aftermarket to dealer)

Labor: 2–5 h

USD, part only. Labor is billed at the shop's hourly rate.

Data: DERATE verified base, updated October 2026

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