A P0402 on the 6.0L Power Stroke tells you the computer sees more exhaust gas recirculation flow than it commands, usually because the EGR valve is stuck open or the system is reading flow incorrectly.
What P0402 means
EGR Flow Excessive is a diagnostic trouble code the engine computer sets when the monitored value falls outside its expected range. On the 6.0L Power Stroke, it points to a specific area of the fuel, air, or emissions system, and reading it correctly saves you from replacing good parts.
Common causes
- EGR valve stuck open from soot buildup
- Sticking or contaminated EGR valve motor
- Faulty EGR position feedback
- Carbon-clogged EGR passages skewing the reading
Symptoms you may notice
- Rough or surging idle
- Hesitation and reduced power
- Increased soot and poor throttle response
- Illuminated check-engine light
How to diagnose it
Scan the EGR position and commanded values and compare them. A valve that will not close, or reads open when commanded shut, confirms the fault. Inspect the valve and passages for the heavy soot that keeps it from seating.
How to fix it
Clean the EGR valve and passages if soot is the cause, or replace the valve if it is worn or the motor has failed. Because the EGR system ties into the cooler, inspect cooler condition while the area is apart. A healthy cooling and emissions system reduces the soot that causes this code to return.
Frequently asked questions
Can I drive with P0402?
You can, but the stuck-open EGR hurts running quality and adds soot. Address it promptly to avoid further buildup.
Is it the valve or a sensor?
Compare commanded versus actual EGR position on a scan tool. A valve that will not close is mechanical; a mismatched reading may be the position feedback.
Will cleaning fix it?
If the valve is simply sooted, cleaning it and the passages often clears the code. A worn valve or failed motor needs replacement.
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