P0402
Medium SeverityEGR Excessive Flow
Emissions System
What Does P0402 Mean?
Too much exhaust gas is being recirculated, causing rough idle and stalling.
Common Fix
Clean or replace EGR valve
Estimated Cost (DIY)
$20 - $150
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 Diagnostic Flowchart
Scroll to load technician if/then branches.
Read live data and freeze frame for P0402 to pinpoint the cause before buying parts.
Ready to fix it yourself?
Find My Vehicle Repair Guide →Select your exact vehicle for a personalized step-by-step guide
Related Resources
Repair guides, symptom pages, and wiring diagrams related to P0402.
OEM Manual Evidence
Browse →A L L Diagnostic Trouble Codes ( DTC ) — 2013 GMC Truck Savana 2500 V8-6.6L DSL Turbo Service Manual | Operation CHARM Operation CHARM : Ca...
A L L Diagnostic Trouble Codes ( DTC ) — 2013 GMC Truck Savana 3500 V8-6.6L DSL Turbo Service Manual | Operation CHARM Operation CHARM : Ca...
A L L Diagnostic Trouble Codes ( DTC ) — 2013 GMC Truck Savana 4500 V8-6.6L DSL Turbo Service Manual | Operation CHARM Operation CHARM : Ca...
A L L Diagnostic Trouble Codes ( DTC ) — 2013 Chevy Truck Express 2500 V8-6.6L DSL Turbo Service Manual | Operation CHARM Operation CHARM :...
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.
Related Repair Guides
If your vehicle has triggered P0402, these DIY repair guides may help: