Exhaust Gas Recirculation Flow Excessive Detected
The P0402 code means the vehicle's onboard diagnostic system has detected: Exhaust Gas Recirculation Flow Excessive Detected. This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- moderate
- Estimated cost
- $100 - $400 (parts and labor)
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Common Symptoms
- Check Engine Light illuminated
- Rough or unstable idle
- Engine surging or hesitation
- Engine stalling at idle
- Pinging or knocking under load
Probable Causes (Ranked by Likelihood)
- EGR valve stuck open Very High
- Carbon buildup holding EGR valve open High
- Faulty EGR pressure feedback sensor (DPFE) Moderate
- Blocked EGR passages causing incorrect readings Low
Common Fixes by Vehicle
What techs usually find when diagnosing P0402 on specific vehicles — tap your vehicle for the fix and the exact part:
2001-2011 Ford Ranger 3.0L/4.0L Easy DIY
The DPFE sensor is the #1 cause of P0402 on Ford Rangers. The sensor reads excessive EGR flow even when the valve is closed. Replace the DPFE sensor (Motorcraft) -- it is a $25 part on the firewall with two rubber hoses. Takes 10 minutes. Confirm the exact part for your year and engine with a retailer's fitment lookup or your VIN before ordering - these applications split by engine and build date.
Labor: 15-30 minutes1999-2007 Chevrolet Silverado 5.3L/4.8L Moderate DIY
Carbon buildup in the EGR passages of the intake manifold causes excessive flow readings. Remove the EGR valve and clean the passages with carburetor cleaner and a long brush. Inspect the EGR valve pintle for carbon deposits. Replace the EGR valve gasket with a new Fel-Pro unit.
Labor: 1-2 hours1998-2007 Honda Accord 2.3L/3.0L Moderate DIY
EGR passages in the intake manifold become clogged with carbon, causing the EGR valve to stick open. Remove the EGR valve and clean the port with a wire brush and carb cleaner. If the valve diaphragm is torn or the valve does not hold vacuum, replace it.
Labor: 1-1.5 hoursFrequently Asked Questions
Can I drive with code P0402?
You can drive short distances, but the engine may idle rough or stall. Excessive EGR flow dilutes the air-fuel mixture at idle, causing drivability problems. Repair promptly to avoid stalling in traffic.
Can I clean the EGR valve instead of replacing it?
Yes. Many EGR valves can be removed and cleaned with carburetor cleaner to remove carbon deposits. If the valve moves freely after cleaning and holds vacuum, it may not need replacement.
Why is P0402 especially common on Ford vehicles?
Ford vehicles with DPFE (Differential Pressure Feedback EGR) sensors are prone to this code. The DPFE sensor fails frequently and gives false high-flow readings, triggering P0402.
What actually makes the computer set an EGR code?
The OBD II regulation requires the system to flag EGR when flow deviates from the manufacturer's specified rate — in either direction, too much or too little — by enough to push emissions past 1.5 times the FTP standards; and, where no EGR fault could do that, when there is no detectable EGR flow at all (Title 13 CCR 1968.2, section (e)(8.2)). Note that excess flow is a malfunction too, which is why an EGR code does not automatically mean a blocked passage. This is the threshold the monitor is designed around, not a description of your specific fault — the regulation says what the system must detect, not how to find it on your vehicle.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Visually inspect the EGR valve for carbon buildup preventing full closure
-
With the engine idling, manually close the EGR valve -- if idle smooths out, the valve is stuck open
-
Test the DPFE sensor by comparing its voltage readings to specifications (typically 0.45V at idle)
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Check EGR vacuum lines and electrical connectors for damage or leaks
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Clean the EGR valve and passages with carburetor cleaner and retest
Sources 2
This page is built from documented references. Verify against your own service info before repair work.
- California Code of Regulations, Title 13 section 1968.2 (OBD II)malfunction criteria, section (e)
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
P0402 on Diesel, EV & Equipment
The same code ID appears across other engines and platforms. The diagnostic flow varies by manufacturer — these are the platform-specific breakdowns:
Commonly Affected Vehicles
- 1997-2010 Ford F-150
- 2000-2008 Ford Taurus
- 1998-2006 Ford Explorer
- 2001-2010 Ford Ranger
- 2003-2012 Honda Accord
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