P0402: Exhaust Gas Recirculation (EGR) Flow Excessive Detected
Updated November 12, 2026
The EGR system feeds a small amount of exhaust back into the engine to lower combustion temperatures. P0402 means the computer is seeing more EGR flow than it commanded, often when the valve should be closed, such as at idle. Too much exhaust at idle makes the engine run rough or stall.
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🔧 Want to check this yourself? An OBD2 scanner reads the code; models with live data also show the sensor readings used in the checks below. See code readers and scanners from $24.99 ↓ · Which scanner do I need?
Common causes
- An EGR valve stuck partly open, often from carbon buildup
- A faulty EGR position or pressure sensor (for example, the DPFE sensor on many Fords) giving a false reading, or cracked sensor hoses
- On older vacuum-operated systems, a faulty EGR vacuum control solenoid applying vacuum when it shouldn't
Code meanings can vary slightly by manufacturer. Use these as a starting point and confirm with your vehicle's service information or a mechanic before replacing parts.
Symptoms
- Rough idle
- Stalling at idle or when coming to a stop
- Hesitation or misfire
- Check engine light
Is it safe to drive?
If the engine stalls, don't drive it in traffic; have it towed, since stalling can cost you power steering and brake assist. If it runs normally with a steady light, get it checked soon.
How to check it with a scanner
- Plug an OBD2 scanner into the port under the dashboard and read all stored codes and the freeze-frame data (the conditions when the code set).
- Scan for other EGR codes, and if your scanner shows it, compare desired and actual EGR position.
- With the engine off and cool, remove the EGR valve following your vehicle's procedure and check for carbon holding it open; clean or replace it with a new gasket.
- On vacuum-operated valves, with the engine off, use a hand vacuum pump to check that the diaphragm holds vacuum and the valve snaps fully closed when released.
- Inspect the EGR pressure sensor hoses for cracks or being swapped.
- After a repair, clear the code and drive normally for a few days to confirm it doesn't come back.
A basic code reader shows the code; scanners with live data let you watch sensor readings, which is what you need for most of the checks above. See OBD2 scanners under $100.
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Questions
What does P0402 mean?
P0402 is the generic OBD2 code for "Exhaust Gas Recirculation (EGR) Flow Excessive Detected." The EGR system feeds a small amount of exhaust back into the engine to lower combustion temperatures. P0402 means the computer is seeing more EGR flow than it commanded, often when the valve should be closed, such as at idle. Too much exhaust at idle makes the engine run rough or stall.
Is it safe to drive with P0402?
If the engine stalls, don't drive it in traffic; have it towed, since stalling can cost you power steering and brake assist. If it runs normally with a steady light, get it checked soon.
How do I check P0402 myself?
Read the code and freeze-frame data with an OBD2 scanner, then: Scan for other EGR codes, and if your scanner shows it, compare desired and actual EGR position. With the engine off and cool, remove the EGR valve following your vehicle's procedure and check for carbon holding it open; clean or replace it with a new gasket. On vacuum-operated valves, with the engine off, use a hand vacuum pump to check that the diaphragm holds vacuum and the valve snaps fully closed when released. Inspect the EGR pressure sensor hoses for cracks or being swapped.
Related codes
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