P0404 on the 6.7L Cummins is an EGR position-related code. It tells you the EGR valve is not reporting the position the ECM expects, which usually means the valve is binding on soot or the position feedback is off. Here is how to read the code and repair it.
What P0404 means
P0404 is defined as Exhaust Gas Recirculation Circuit Range/Performance. The 6.7L Cummins EGR valve has a position sensor that tells the ECM where the valve actually is. When commanded position and reported position do not agree, or the feedback is out of range, the ECM sets P0404. On this engine it typically means the valve is sticking or the sensor circuit is faulty.
Common causes
- Soot buildup causing the EGR valve to stick or move slowly
- Failed EGR valve actuator motor
- Faulty EGR position sensor
- Corroded or damaged connector and wiring on the EGR circuit
- Internal EGR valve wear affecting feedback accuracy
Symptoms
- Check engine light with stored P0404
- Rough idle or hesitation
- Reduced power or limp mode
- Failed or incomplete regens
- Elevated exhaust temperatures in some cases
How to diagnose it
Command the EGR valve open and closed with a scan tool while watching position feedback. A valve that lags, sticks, or cannot reach commanded position confirms a mechanical or actuator problem. If feedback is erratic or reads out of range at rest, suspect the position sensor or wiring. Inspect the connector for corrosion and check the harness for chafing. On high-mile 6.7L Cummins, carbon binding is the leading cause of P0404.
How to fix it
Clean the valve if soot is causing it to bind, or replace the EGR valve assembly if the actuator or internal feedback has failed. Repair corroded connectors and damaged wiring. Replace a proven-faulty position sensor. After the repair, clear the code and command the valve through its range to confirm smooth, accurate feedback, then complete a drive cycle to verify the code stays off.
Frequently asked questions
What is the difference between P0404 and P0401?
P0404 is about the valve's position feedback being out of range or not matching command, while P0401 is about actual EGR flow being too low.
Can cleaning fix P0404?
If soot is causing the valve to stick, cleaning can restore proper movement. If the actuator or position sensor has failed, the valve needs replacement.
Is P0404 safe to drive with?
You can usually drive short distances, but a binding EGR valve can cause limp mode and failed regens, so repair it soon.
Need parts or a second opinion? The team at Core Diesel Parts can help you match the right components to your engine. Email sales@coredieselparts.com with your VIN and symptoms and we will point you to the correct parts.
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