What Does P0404 Mean?
The EGR (Exhaust Gas Recirculation) valve's actual position or flow does not match what the ECM is commanding. The ECM monitors the difference between the commanded EGR position and the actual position reported by the feedback sensor, and this discrepancy has exceeded the acceptable range. The driver may notice rough idle, hesitation under load, or engine surging. This code indicates the EGR system is functioning but not accurately.
Common Causes
35%
Carbon buildup on the EGR valve pintle restricting movement range
25%
Faulty EGR position sensor providing inaccurate feedback to the ECM
20%
EGR valve motor or actuator weakened — cannot achieve full travel
12%
Wiring issue causing intermittent position sensor signal
8%
Vacuum leak in EGR vacuum supply (vacuum-operated systems)
Diagnostic Steps
1
Monitor EGR commanded position vs. actual position PIDs at idle and under load — the actual position should track the commanded position within 5-10%. Identify at what point the discrepancy occurs.
2
Command the EGR to various positions (0%, 25%, 50%, 75%, 100%) using bidirectional control and verify the position sensor reads back within tolerance at each step.
3
Remove the EGR valve and manually move the pintle — it should move freely through its full range. Inspect for carbon buildup or mechanical binding.
4
Check the position sensor reference voltage (typically 5V) and ground at the connector. A sagging reference voltage will cause inaccurate position readings.
5
Clean the EGR valve thoroughly with carburetor cleaner, reinstall, and clear codes. If the code returns, replace the EGR valve assembly.
Estimated Repair Cost
$100 - $400
Parts + labor, varies by vehicle and location
The EGR (Exhaust Gas Recirculation) valve's actual position or flow does not match what the ECM is commanding. The ECM monitors the difference between the commanded EGR position and the actual position reported by the feedback sensor, and this discrepancy has exceeded the acceptable range. The drive...
The most common cause of P0404 (Exhaust Gas Recirculation Circuit Range/Performance) is: Carbon buildup on the EGR valve pintle restricting movement range
Typical repair costs for P0404 range from $100 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive in most cases. The engine management system can compensate to some degree. The vehicle will likely fail emissions testing. Occasional rough idle or hesitation may occur. Repair at your convenience.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0404 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions Control / EGR System
Difficulty
Type
Generic (SAE)
Recommended Tools
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