P0404 - Exhaust Gas Recirculation Circuit Range/Performance
P0404 is an EGR flow, feedback, or control fault. Confirm whether the problem is carbon restriction, valve movement, vacuum/control, sensor feedback, or wiring.
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Compare trims at idle, 2500 RPM, and cruise before pricing sensors.
Check intake boots, PCV hoses, and post-MAF leak paths.
Inspect MAF contamination and airflow data after intake leaks are considered.
Look for cracked ducts, loose clamps, and unmetered air after the MAF.
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Code Overview
P0404 is an EGR flow, feedback, or control fault. Confirm whether the problem is carbon restriction, valve movement, vacuum/control, sensor feedback, or wiring.
Common Causes
- Carbon-restricted EGR passages, valve pintle, intake port, or tube
- EGR valve stuck open or closed
- EGR solenoid, vacuum supply, DPFE/pressure feedback, or position sensor fault
- Wiring, connector, or control circuit issue
- Exhaust backpressure, intake leak, or fuel-control problem affecting flow test results
Symptoms
- Check engine light
- Pinging under load
- Rough idle or stalling if EGR sticks open
- Failed emissions test
- Reduced fuel economy
Diagnostic Steps
- Confirm whether the fault is insufficient flow, excessive flow, circuit, or sensor feedback
- Inspect vacuum hoses, solenoid plumbing, EGR tube, valve, and passages for carbon or leaks
- Command EGR and watch idle quality, MAP/MAF change, and feedback data where supported
- Check DPFE/pressure feedback hoses and sensor readings on Ford-style systems
- Verify power, ground, and control circuits before replacing electronic EGR valves
- After repair, road test under monitor conditions and confirm no pinging, stalling, or pending EGR codes
Repair Difficulty
Moderate
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