DURAMAX-P0409 moderate Duramax ›

Exhaust Gas Recirculation Sensor "A" Circuit

The DURAMAX-P0409 (Duramax) diesel fault code means: Exhaust Gas Recirculation Sensor "A" Circuit. This is a moderate severity code.

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Keep driving?
Yes, with caution
DIY difficulty
intermediate
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What Are the Symptoms of DURAMAX-P0409?

  • Check Engine Light on
  • Possible reduced power

What Causes DURAMAX-P0409? (Most Likely First)

  • Failed EGR sensor High
  • Open or shorted sensor wiring High
  • Corroded or damaged connector Moderate
  • Engine computer input fault Low

Can I Still Drive with DURAMAX-P0409?

Yes, with caution. DURAMAX-P0409 is rated moderate severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.

Frequently Asked Questions

What does P0409 mean on a Duramax?

P0409 means Exhaust Gas Recirculation Sensor "A" Circuit. The engine computer has detected a fault in the EGR sensor "A" circuit.

Is P0409 a Duramax-specific code?

No. P0409 is a generic OBD-II code defined by SAE J2012, so it means the same thing on any vehicle that sets it. The exact conditions GM uses to set it on its diesels are in GM service information.

Mechanics Guide Step-by-step diagnosis

How Do You Diagnose DURAMAX-P0409?

  1. Find which sensor is EGR sensor "A" on your engine in the service information.

  2. Inspect the connector and harness for heat damage.

  3. Check the sensor reference voltage, ground and signal circuits.

Sources 1

This page is built from documented references. Verify against your own service info before repair work.

  • SAE J2012Diagnostic Trouble Code Definitions (defines P0409 as a generic OBD-II code)

P0409 on Other Platforms

The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown:

Gas / Automotive (OBD-II) Generic OBD-II definition for P0409 Kubota moderate EGR Sensor Correlation (A/B)

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More Duramax codes → Diesel home All diesel codes Heavy-duty Guides

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