P0402 - Exhaust Gas Recirculation Flow Excessive Detected

EGR flow is higher than expected.

Treat the code as the starting point: compare symptoms, likely causes, and repair paths before pricing parts or moving into an estimate.

Code Overview

EGR flow is higher than expected.

Common Causes

• EGR valve stuck open
• Control solenoid holding the valve on
• Carbon preventing the EGR valve from seating
• Feedback sensor reporting flow incorrectly

Symptoms

• Rough idle or stalling
• Stumble off idle
• Check-engine light with reduced combustion stability

Diagnostic Steps

1. Inspect the EGR valve for sticking or carbon buildup
2. Check whether the valve is being commanded open when it should be closed
3. Inspect vacuum or electronic control components for constant EGR command
4. Compare EGR feedback data to actual engine behavior if equipped

Repair Difficulty

Moderate

General difficulty estimate for the most common repair path.

Likely Repairs & Cost Guides

Use symptoms, scan data, and quick checks to confirm the likely repair path before pricing parts. The estimator helps compare repair paths before replacing anything unnecessarily.

Related OBD Codes

Browse nearby code-family pages when the same fault pattern overlaps across systems, such as misfire, lean fuel trim, EVAP sealing, cooling, or charging faults.

Next Steps

Move from code lookup to diagnosis, then estimate the likely repair only after symptoms, causes, and checks point to the same path.