Exhaust Gas Recirculation Flow Excessive Detected
The DURAMAX-P0402 (Duramax) diesel fault code means: Exhaust Gas Recirculation Flow Excessive Detected. This is a moderate severity code.
- Keep driving?
- Yes, with caution
- DIY difficulty
- intermediate
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What Are the Symptoms of DURAMAX-P0402?
- Check Engine Light on
- Rough idle or stalling
- Black smoke
- Loss of power
What Causes DURAMAX-P0402? (Most Likely First)
- EGR valve stuck open High
- EGR valve position sensor reading incorrectly Moderate
- Airflow sensor reading incorrectly Moderate
Can I Still Drive with DURAMAX-P0402?
Yes, with caution. DURAMAX-P0402 is rated moderate severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.
Frequently Asked Questions
What does P0402 mean on a Duramax?
P0402 means Exhaust Gas Recirculation Flow Excessive Detected. The engine computer has measured more exhaust gas recirculation flow than it commanded.
Is P0402 a Duramax-specific code?
No. P0402 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-P0402?
Command the EGR valve with a scan tool and compare commanded and actual position.
Inspect the EGR valve and passages for soot buildup.
Check the airflow reading, which the computer often uses to judge EGR flow.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines P0402 as a generic OBD-II code)
P0402 on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown:
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