OBD codes / P0402
P0402
ModerateExhaust Gas Recirculation (EGR) Flow Excessive
P0402 is generally safe to drive with short-term, though the rough idle or stalling at stops can be annoying and occasionally inconvenient. It's low-risk mechanically. Try cleaning the EGR valve and passages before replacing parts — a stuck-open valve from carbon is the common cause.
What this code means
The EGR system routes a measured amount of exhaust back into the intake to lower combustion temperatures and emissions. P0402 means too MUCH is flowing — the opposite of P0401. The usual cause is an EGR valve stuck open, often from carbon holding it off its seat, or a faulty EGR position sensor reporting the wrong amount. Excess exhaust at idle dilutes the mixture, so the classic symptom is a rough idle or stalling at stops. A cleaning often fixes it.
Symptoms you might notice
- Rough idle or stalling, especially at stops
- Hesitation at low speed
- Check-engine light
- Failed emissions test
What it costs to fix
Typical range: $100–$500 · about ~0.5–2.5 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| EGR clean (labor-only) | $0–$20 | ~1–2.5 hrs |
| EGR valve | $50–$300 | ~0.5–1.5 hrs |
| EGR position sensor | $25–$100 | ~0.3–1 hrs |
Cleaning out the carbon that holds the valve open is the cheap, common fix and may be labor-only. A new valve is modest; the sensor is cheaper. Cost climbs only if the EGR is buried in the intake.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0402 for my exact vehicle →
Frequently asked
Can I drive with P0402?
Usually yes, short-term — it mainly causes a rough idle or stalling at stops. It's not a major safety issue, so you can drive to get it cleaned or diagnosed; fix it before an emissions test.
What's the difference between P0401 and P0402?
Opposite problems: P0401 is too LITTLE EGR flow (often a clogged valve/passages), P0402 is too MUCH (often a valve stuck open). Both are frequently solved by cleaning, but they point in opposite directions.
Will cleaning fix P0402?
Often — carbon holding the EGR valve open is the most common cause, and a thorough cleaning frequently restores proper flow. If it returns quickly, the valve or position sensor may need replacing.
How much does it cost to fix P0402?
Frequently inexpensive — a clean may be labor-only, and a valve or sensor is modest. Cost only rises if the EGR is buried in the intake and takes real disassembly to reach.
Seeing P0402 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P0402 for my vehicleGeneric OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.