What does P0402 mean?
The ECM detected excessive EGR flow.
Quick Decision Guide
- Carbon-clogged EGR passage
- Sticking EGR valve
- Vacuum control issue
When to stop driving
Usually safe short-term if the vehicle runs normally, but diagnose soon to prevent drivability and emissions issues.
Reviewed by ratchit Automotive Solutions for clarity and inspection-first safety framing. Not a substitute for professional diagnosis.
Repair Decision & Cost Guide
Use this guide to decide what to inspect first, what it may cost, and when to move from DIY checks to professional diagnosis.
P0402 does not automatically mean the catalytic converter has failed. It may involve O2 sensor behavior, exhaust leaks, fuel trim, or unresolved misfires — inspect upstream causes before replacing the converter.
DIY vs. Shop
Can you keep driving?
Best first DIY check
Don't replace this first
When to seek a shop
Recommended next action
Estimated Repair Cost
Inspection cost
$0–$25 DIY scanner
Shop diagnostic cost
$80–$150 (typical shop diagnostic fee)
Shop repair cost
$100–$4,000
Diagnostic uncertainty: This code points to a system or condition, not a guaranteed failed part. Inspect before replacing.
Cost variation: Costs vary by vehicle, location, part quality, labor rate, and the confirmed root cause.
Inspect Before Replacing
These checks are cheap, fast, and rule out the most common causes before spending money on parts.
- 1Inspect EGR passages for carbon restriction.
- 2Check vacuum lines or electronic control wiring.
Track this emissions issue
Save this issue to My Garage, track what you inspect, and build service history for this vehicle.
V-IQ readiness preview: Medium impact — resolving and tracking this issue may improve your V-IQ readiness. Tracking active codes and resolutions builds a service history we use to estimate V-IQ readiness over time.
Understanding P0402 in detail
P0402 points to exhaust gas recirculation flow or control behavior outside the expected range. EGR faults may come from carbon buildup, a sticking valve, clogged passages, vacuum control issues, wiring faults, or sensor feedback problems. Inspect carbon restriction and control signals before replacing the EGR valve.
Symptoms of P0402
- Check engine light
- Rough idle
- Ping or knock
- Hesitation
- Failed emissions test
- Poor fuel economy
Common causes
- Carbon-clogged EGR passage
- Sticking EGR valve
- Vacuum control issue
- Faulty EGR sensor
- Damaged wiring
- DPFE or feedback issue
How to diagnose P0402
Steps ordered by urgency — tackle Now items first.
- NowInspect EGR passages for carbon restriction.
- NowCheck vacuum lines or electronic control wiring.
- SoonReview commanded vs actual EGR behavior with a scan tool.
- SoonInspect related sensors and connectors.
- LaterClean passages before replacing the valve when carbon is present.
How to fix P0402
Fixes listed in order of likelihood and cost-efficiency.
- 1Clean EGR passages
- 2Repair vacuum or wiring issue
- 3Replace EGR valve after testing
- 4Replace EGR feedback sensor
- 5Repair control solenoid issue
Want to check your full vehicle?
Run a free maintenance scan to see what else needs attention based on your year, make, model, mileage, and climate.
Recommended tools & parts
These recommendations appear because this issue commonly requires inspection in this system area. ratchit does not recommend replacing parts until the likely cause is confirmed.
O2 Sensor & Catalyst Inspection Kit
Confirm O2 sensor behavior and exhaust integrity before replacing the catalytic converter
Check O2 sensor behavior before replacing the catalytic converter Verify fitment for your year/make/model.
Sensor & Diagnostic Kit
Test and replace common engine sensors — O2, MAF, cam/crank
Check sensor behavior before replacing parts Verify fitment for your year/make/model.
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Estimated Repair Cost — P0402
Ranges vary by vehicle, region, and shop. Use as a ballpark — always get a quote.
DIY estimate
$10 – $100
Shop estimate
$100 – $350
DIY estimate
$50 – $300
Shop estimate
$250 – $1,000
DIY estimate
$200 – $1,200
Shop estimate
$800 – $4,000
Cost data is estimated and may not reflect your specific vehicle or location.
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Frequently Asked Questions
Track this emissions issue — track what you inspect and build service history for this vehicle.
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