P0402
Medium SeverityEGR Excessive Flow
Emissions System
P0402 — Instant Answer
EGR Excessive Flow
Severity: MEDIUM SEVERITY
Meaning: Too much exhaust gas is being recirculated, causing rough idle and stalling.
Safe to drive? Usually yes with caution, but confirm root cause before long trips.
Estimated repair cost: $20 - $150
Most common causes:
- 1. EGR valve stuck open (35-45% of cases)
- 2. Carbon holding EGR open (10-25% of cases)
- 3. Faulty EGR control solenoid (10-25% of cases)
Symptoms
- ⚠️Rough idle
- ⚠️Stalling at idle
- ⚠️Hesitation
- ⚠️Check engine light
Related Symptoms
Common Causes
How to Diagnose P0402
- 1Inspect EGR valve for carbon
- 2Check EGR solenoid
- 3Clean or replace EGR valve
OEM Procedures for P0402
P0402 affects the EGR Valve. Found 8 OEM service manual procedures.
Adjustment/Replacement - Specification
Adjustment/Replacement - Specification
Adjustment/Replacement - Specification
Adjustment/Replacement - Specification
Adjustment/Replacement - Specification
Adjustment/Replacement - Specification
Adjustment/Replacement - Specification
Adjustment/Replacement - Specification
OEM Diagnostic Flowchart
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Related Resources
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Related Symptoms
Browse →Rough idle often traces back to ignition, air metering, vacuum leaks, or timing-related faults before it becomes a full misfire complaint.
A check-engine light is a graph entry point into code pages, symptom-specific diagnosis, and the exact repair categories most often associated with those failures.
Exact Vehicle Hubs
Browse →Open the exact vehicle hub for a repair workflow commonly associated with P0402.
Open the exact vehicle hub for a repair workflow commonly associated with P0402.
Open the exact vehicle hub for a repair workflow commonly associated with P0402.
Open the exact vehicle hub for a repair workflow commonly associated with P0402.
Open the exact vehicle hub for a repair workflow commonly associated with P0402.
Open the exact vehicle hub for a repair workflow commonly associated with P0402.
Exact Repair Workflows
Browse →Open the exact repair flow most commonly associated with P0402 on this vehicle.
Open the exact repair flow most commonly associated with P0402 on this vehicle.
Open the exact repair flow most commonly associated with P0402 on this vehicle.
Open the exact repair flow most commonly associated with P0402 on this vehicle.
Open the exact repair flow most commonly associated with P0402 on this vehicle.
Open the exact repair flow most commonly associated with P0402 on this vehicle.
Related Codes
The EGR system flow is not within expected parameters.
The EGR is not flowing enough exhaust gas. Usually carbon buildup blocking the passages.
The EGR valve control solenoid or motor has a circuit fault.
Frequently Asked Questions
- Why does a stuck-open EGR cause rough idle?
- At idle, the engine does not need EGR. Extra exhaust gas dilutes the fuel mixture, making it too lean to idle properly.
- Can a stuck EGR cause stalling?
- Yes — if the EGR is stuck wide open at idle, the engine gets too much inert gas and cannot maintain idle.
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Author & Review
Written by AllOEMManuals Editorial Team. Reviewed by ASE-certified technicians and updated with factory-reference checks for fitment-sensitive steps.
This guide was drafted with AI assistance and reviewed for accuracy by a human editor.
Last updated: 2026-05-07