DURAMAX-P220A serious Duramax ›

NOx Sensor Circuit Bank 1 Sensor 2

The DURAMAX-P220A (Duramax) diesel fault code means: NOx Sensor Circuit Bank 1 Sensor 2. This is a serious severity code.

Unverified. We could not confirm this code's definition against freely available manufacturer documentation, so treat the meaning, severity and fix guidance on this page as unconfirmed. Check it against the manufacturer's service information for your exact model and serial range before acting on it. This page is kept out of search engines for that reason, and we are working through this family manual by manual.

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Keep driving?
Yes, with caution
DIY difficulty
advanced
Estimated cost
$300-$500 NOx sensor, $200 DEF injector, $2,500-$4,500 full SCR replacement
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What Are the Symptoms of DURAMAX-P220A?

  • Check Engine Light
  • 'Service Emissions System' or 'Service DEF System' message
  • Countdown to speed limit reduction (5 mph eventually) if uncorrected
  • Extra DEF consumption
  • DPF regen occurring more frequently

What Causes DURAMAX-P220A? (Most Likely First)

  • Downstream (post-SCR) NOx sensor fault Very Likely
  • Contaminated DEF fluid (use ONLY API-certified DEF) Likely
  • DEF injector clogged with crystallized urea Possible
  • NOx sensor end-of-life (typical 100-150K miles) Possible
  • Wiring or connector fault at sensor Possible

Can I Still Drive with DURAMAX-P220A?

Yes, with caution. DURAMAX-P220A is rated serious severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.

Frequently Asked Questions

What is P220A on a Duramax?

Duramax code P220A (NOx Sensor Circuit Bank 1 Sensor 2) is a serious-severity diagnostic trouble code triggered by the engine control module when it detects a problem in the associated system. ALWAYS use API-certified DEF from a sealed container. Contaminated or wrong DEF is the #1 cause of SCR system failure.

Is a Duramax P220A safe to drive?

Short-term yes, but the PCM enters a countdown that reduces top speed to 5 mph if the fault isn't cleared. Repair before hitting 0 miles remaining.

How much does it cost to fix P220A on a Duramax?

NOx sensor $300-$500 installed. DEF injector $200-$400. SCR catalyst $2,500-$4,500.

Mechanics Guide Step-by-step diagnosis

How Do You Diagnose DURAMAX-P220A?

  1. Scan for all SCR codes together — a single NOx sensor failure often cascades into multiple DTCs

  2. Verify DEF quality — use a refractometer or DEF test strips (should be 32.5% urea ± 0.5%)

  3. Inspect the DEF injector for crystallized urea deposits; clean or replace

  4. If both upstream and downstream NOx sensors are reading the same value at idle, one may be failed

  5. Use Tech 2 / GDS2 to run SCR performance tests after repair to clear countdown

Sources 1

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

  • SAE J2012Diagnostic Trouble Code Definitions (defines P220A as a generic OBD-II code)

Which Vehicles Commonly Get DURAMAX-P220A?

  • 2011-2016 Chevy Silverado 2500/3500 HD 6.6L Duramax LML
  • 2011-2016 GMC Sierra 2500/3500 HD 6.6L Duramax LML
  • 2017+ Chevy Silverado 2500/3500 HD 6.6L Duramax L5P
  • 2017+ GMC Sierra 2500/3500 HD 6.6L Duramax L5P

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