OBD-II Code · Emissions
P0402
EGR Flow Excessive
Severity
medium
Worth booking. It costs fuel, emissions or comfort until it is fixed.
Can you drive it
Only if running normally
A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety.
Indicative cost (USD)
$100–$500
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
Too much EGR flow.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
- Rough idle
- Stalling
Likely causes
- Stuck open EGR valveMost common
- Leaking EGR gasket
Read the full diagnostic procedureP0402 is the opposite of P0401 — excessive EGR flow.
P0402 is the opposite of P0401 — excessive EGR flow. The ECM commanded the valve toward closed (or completely closed during idle, where EGR should be zero) but is still seeing exhaust gas in the intake stream via MAP/MAF/DPFE signal. The dominant cause on gas engines past 80,000 miles is a carbon-coked pintle that won't seat fully closed: chunks of baked-on soot sit between the pintle and the seat, exhaust leaks past at idle, and the engine runs rough or stalls at stoplights with a P0402 stored.
Diagnostic ladder
- pull the valve, look at the seat under good light, and check for a visible gap or carbon flakes preventing seating; the pintle should snap closed under spring pressure with zero gap when uncommanded.
- Scan-tool EGR position live data at idle — a healthy valve reads pintle-closed (typically <0.7V on the position sensor); a stuck-partially-open valve reads 0.9-1.5V at idle and that's your code.
- Other common cause: a torn EGR valve diaphragm on older vacuum-operated valves (pre-2005 Toyota, GM, Chrysler) where intake vacuum pulls the valve open at idle when it should be closed — pinch the vacuum line at the valve and see if the rough idle clears.
- On DPFE-equipped Fords, a leaking DPFE rubber hose can over-report flow and trigger P0402 even with a perfectly sealing valve.
Vehicle-specific patterns2003-2010 GM 3.5/3.9L V6 (Impala, Malibu, Uplander, Lucerne) is the textbook P0402 — the linear EGR valve pintle cokes up with carbon and won't fully…
- 2003-2010GM 3.5/3.9L V6 (Impala, Malibu, Uplander, Lucerne) is the textbook P0402 — the linear EGR valve pintle cokes up with carbon and won't fully seat, idle goes rough, and the code throws within a few drive cycles; clean the seat with carb cleaner if the pintle isn't pitted, otherwise replace ($90-$160 part).
- 2000-2007Chrysler/Dodge 3.3/3.8L V6 (Caravan, Town & Country) throws P0402 from a stuck EGR solenoid valve that won't fully close — common enough that aftermarket valves come with a TSB-style cleaning kit.
- 1998-2004Toyota 4Runner/Tacoma with the 5VZ-FE 3.4L V6 throws P0402 from a torn EGR modulator diaphragm bleeding vacuum to the valve at idle — modulator is $40, valve is fine.
- 2005-2010Ford Mustang 4.0L SOHC V6 throws P0402 from a stuck-open valve combined with a leaking DPFE hose — replace both the hose and the valve to clear it permanently.
Estimated repair$30 (carb cleaner DIY) to $300+ (valve + position sensor + gasket).
Look up another code
P0402 — frequently asked
What does a P0402 code mean?
Too much EGR flow.
What causes a P0402 code?
Common causes: Stuck open EGR valve; Leaking EGR gasket.
What are the symptoms of a P0402 code?
Typical symptoms: Check engine light; Rough idle; Stalling.
Is it safe to drive with a P0402 code?
Only if running normally. A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety. Estimated repair: $100-$500.
How do I diagnose a P0402 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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