P0404
Fix within a few daysYour engine's computer detected that the Exhaust Gas Recirculation (EGR) valve is not opening or closing as expected, or its position is outside the normal operating range.
Code P0404 means your EGR valve isn't working correctly. Common causes: Stuck EGR valve (70%), clogged EGR passages (20%). Drivability: Yes, safe to drive, but fix soon. Repair cost: $90-$330 DIY, $200-$600 professional.
Can I Drive With P0404?
Yes, for short trips only
Essential trips under 10 miles, avoid highways and heavy acceleration. Fix within a few days.
Stop driving immediately if: Engine stalls frequently, severe power loss, or loud knocking noises.
Symptoms of P0404
- 1Check Engine Light is on
- 2Rough or unstable idle
- 3Engine stalling, especially at idle
- 4Reduced engine power or acceleration
- 5Engine knocking or pinging (detonation)
- 6Increased fuel consumption
Common Causes of P0404
Parts most likely causing this code, ranked by probability
Carbon buildup or an internal electrical failure prevents the EGR valve from opening or closing properly.
70% of P0404 cases are fixed by replacing the EGR valve
Carbon deposits restrict the flow of exhaust gas through the EGR system, preventing the computer from seeing the expected flow.
20% of P0404 cases are fixed by cleaning clogged EGR passages
If your vehicle uses a separate solenoid or motor to control the EGR valve, a failure here prevents proper valve operation.
5% of P0404 cases are fixed by replacing the EGR solenoid or motor
Damaged wires or corroded connectors to the EGR valve or solenoid can disrupt the control signal or feedback.
5% of P0404 cases are fixed by repairing wiring or connectors
Check These First (Before Buying Parts)
- Visually inspect the EGR valve and any attached vacuum lines for obvious damage, cracks, or disconnections.
- Check for any loose electrical connectors at the EGR valve or solenoid.
- Listen for any vacuum leaks around the EGR system if your vehicle uses a vacuum-operated valve.
How to Diagnose P0404
- 1Visually inspect the EGR valve and its vacuum lines (if applicable) for damage or disconnections.
- 2Check for carbon buildup around the EGR valve pintle and in the EGR passages.
- 3Use a vacuum pump to test a vacuum-operated EGR valve, observing if it holds vacuum and opens.
- 4Use a scan tool to command the EGR valve open and closed, monitoring its position sensor feedback.
- 5Test the electrical resistance of the EGR valve's solenoid or motor and check for proper voltage supply.
- 6If passages are suspected, remove the EGR valve and inspect/clean the intake manifold passages.
P0404 on Popular Vehicles
Ford F-150
2004-2014Known for EGR valve failures due to carbon buildup, especially on 4.6L and 5.4L engines. Clogged EGR passages in the intake manifold are also a common contributing factor.
80% fixed by replacing EGR valve and/or cleaning passages
Chevrolet Silverado
2007-2013EGR valve issues are frequent, often leading to rough idle and reduced performance. Carbon buildup is the primary culprit, affecting the valve's ability to open and close correctly.
75% fixed by replacing EGR valve
Honda Accord
2003-2007Some Accord models experience P0404 due to a sticky or failed EGR valve. Cleaning the valve and ensuring the intake manifold's EGR port is clear often resolves the problem.
70% fixed by cleaning or replacing EGR valve
Frequently Asked Questions
What does P0404 mean?
P0404 indicates that your vehicle's computer has detected an issue with the Exhaust Gas Recirculation (EGR) system's control circuit, specifically that the EGR valve is not performing within its expected range.
Can I drive with P0404?
Yes, you can drive with P0404, but you should fix it within a few days. Ignoring it can lead to rough idling, reduced power, and eventually more expensive repairs.
Will P0404 clear itself?
No, P0404 will not clear itself. The underlying mechanical or electrical issue causing the EGR valve to malfunction must be repaired before the code will clear. Clearing the code without fixing the problem will result in it returning.
How do I fix P0404 myself?
You can fix P0404 yourself by first inspecting the EGR valve and its vacuum lines for damage or carbon buildup. If the valve is stuck, you can try cleaning it with EGR cleaner. If cleaning does not work, replacing the EGR valve is the next step. You may also need to clean the EGR passages in the intake manifold.
How much does it cost to fix P0404?
Fixing P0404 yourself typically costs $90-$330 for parts like a new EGR valve and gaskets. Professional repair at a shop will cost $200-$600, including parts and labor.
P0404 keeps coming back - why?
P0404 keeps coming back because the root cause was not fully addressed. This often happens if only the EGR valve was replaced, but the EGR passages in the intake manifold remain clogged with carbon, or if there's an underlying electrical issue that was overlooked.
Will P0404 fail emissions/smog test?
Yes, P0404 will cause your vehicle to fail an emissions or smog test. The EGR system is a critical component of your vehicle's emissions control, and a malfunction will prevent it from passing inspection.
What's the difference between P0404 and P0401?
P0404 indicates a general range or performance problem with the EGR valve's control circuit, meaning it's not moving as expected. P0401 specifically means 'EGR Flow Insufficient Detected,' indicating that the computer commanded the EGR valve open but did not detect enough exhaust gas flow.
P0404 on Ford F-150?
P0404 is common on Ford F-150s, particularly older models with the 4.6L or 5.4L engines. The most frequent cause is a faulty or carbon-clogged EGR valve, often accompanied by clogged EGR passages in the intake manifold. Cleaning or replacing the EGR valve and ensuring clear passages usually resolves the issue.
Questions to Ask Your Mechanic
Did you test the EGR valve's actual movement and position sensor feedback with a scan tool?
Good answer: Yes, I commanded the EGR valve open and closed and monitored the feedback. It was sticking at X% or not responding as expected.
Did you check for carbon buildup in the EGR passages in the intake manifold?
Good answer: Yes, I removed the EGR valve and inspected the passages. They were partially or fully clogged, which I've now cleaned.
Repair Cost Estimate
DIY Repair
Parts only
$90-$330
Shop Repair
Parts + labor
$200-$600
Save $110-$270 by doing it yourself
Difficulty
intermediate
Time
1-3 hours
Intermediate - requires basic mechanical skills, possibly a vacuum pump or scan tool for proper diagnosis, and careful cleaning of carbon deposits.
Cost of Waiting
Ignoring P0404 can lead to persistent rough idling, engine stalling, reduced fuel economy, and increased harmful emissions. Continued operation with a faulty EGR system can also cause engine knocking (detonation), which can damage internal engine components over time. A $100-$300 EGR valve replacement now prevents potential engine damage later.
While You're In There...
Always replace the gasket when removing or replacing the EGR valve to ensure a proper seal and prevent exhaust leaks.
If you are cleaning EGR passages, it's a good time to clean the throttle body as well, as carbon buildup often occurs in both areas.
Tools You'll Need
- Basic socket set
- Wrenches
- Screwdrivers
- EGR cleaner
- Vacuum pump (for vacuum-operated EGR valves)
- OBD-II scan tool (to monitor data and clear code)
- Torque wrench
P0404 is a common emissions code. Most repairs involve replacing or cleaning the EGR valve, which is a straightforward job for an intermediate DIYer, and your engine will run much smoother afterward.
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Your Next Steps
Step 1: Visually inspect the EGR valve and all associated vacuum lines and electrical connectors for any obvious damage or disconnections.
Step 2: If no obvious issues are found, remove the EGR valve and inspect it for heavy carbon buildup. Try cleaning the valve and the EGR passages in the intake manifold with a dedicated EGR cleaner.
Step 3: If cleaning does not resolve the issue, or if the valve is electronically faulty, you will likely need to replace the EGR valve. Ensure you use a new gasket during reinstallation.