P0404: Exhaust Gas Recirculation Circuit Range/Performance
Updated November 13, 2026
The EGR valve lets a small amount of exhaust back into the intake to lower combustion temperatures. P0404 means the computer sees the EGR valve's position or flow not matching what it commanded: the valve may be sticking, slow, or reporting a position that doesn't make sense.
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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
- Carbon buildup making the EGR valve stick partly open or closed
- A failed EGR valve or its built-in position sensor
- A wiring or connector problem at the EGR valve
- On vacuum-operated systems, a cracked vacuum hose or failed EGR vacuum control solenoid
- On some Ford engines, a faulty DPFE (EGR pressure feedback) sensor or its cracked hoses
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
- Check engine light
- Rough idle or stalling if the valve sticks open
- Hesitation or pinging under load
- Failed emissions test
Is it safe to drive?
If the engine stalls or idles so roughly it might stall, don't drive it; get it fixed or towed. If it runs normally with a steady light, it's usually safe to drive gently for a short time, but 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 related EGR codes and, if your scanner supports it, command the EGR valve and compare desired and actual position in live data.
- With the engine off, inspect the EGR valve connector and wiring, and any vacuum hoses or DPFE sensor hoses for cracks.
- On a vacuum-operated valve, use a hand vacuum pump to apply vacuum and see whether it moves and holds.
- If you remove the valve to check for carbon, use a new gasket. Keep hands clear of the belts and fan whenever the engine is running.
- 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 P0404 mean?
P0404 is the generic OBD2 code for "Exhaust Gas Recirculation Circuit Range/Performance." The EGR valve lets a small amount of exhaust back into the intake to lower combustion temperatures. P0404 means the computer sees the EGR valve's position or flow not matching what it commanded: the valve may be sticking, slow, or reporting a position that doesn't make sense.
Is it safe to drive with P0404?
If the engine stalls or idles so roughly it might stall, don't drive it; get it fixed or towed. If it runs normally with a steady light, it's usually safe to drive gently for a short time, but get it checked soon.
How do I check P0404 myself?
Read the code and freeze-frame data with an OBD2 scanner, then: Scan for related EGR codes and, if your scanner supports it, command the EGR valve and compare desired and actual position in live data. With the engine off, inspect the EGR valve connector and wiring, and any vacuum hoses or DPFE sensor hoses for cracks. On a vacuum-operated valve, use a hand vacuum pump to apply vacuum and see whether it moves and holds. If you remove the valve to check for carbon, use a new gasket. Keep hands clear of the belts and fan whenever the engine is running.
Related codes
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