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P0402 P0xxx · 动力总成（P） 中严重度
Exhaust Gas Recirculation Flow Excessive Detected
Too much exhaust gas is entering the intake. The EGR valve is stuck open or the flow signal is over-reading, starving the mixture of oxygen.
严重程度说明： 中——已影响行驶或排放，请本周内安排检修
你会注意到的故障现象
- Rough idle or stalling
- Lack of power
- Black smoke on diesels
- Hard starting when hot
常见原因
按可能性从高到低排列——从最上面开始查。
- 1 EGR valve stuck open from carbon
- 2 Faulty EGR position sensor
- 3 Short in the signal circuit
- 4 Incorrect valve fitted after a repair
如何排查
先做花钱最少、侵入最小的检查——大多数这类码不是零件问题。
- ✓ Watch EGR actual vs commanded position at idle — a valve that should be closed but is not confirms the fault.
- ✓ Remove and inspect the valve for carbon holding it open.
- ✓ Check the position sensor signal sweeps smoothly across its range.
- ✓ Blank the passage briefly with a test plate to confirm the symptom disappears.
维修方案
- Clean or replace the EGR valve
- Clean the EGR passages in the manifold
- Repair the position sensor wiring
P0402 —— 常见问题
Can I blank off the EGR? +
For off-road or test purposes only. On road vehicles it is illegal in most markets and will fail inspection.
Why does it stall at idle? +
Exhaust gas displaces oxygen in the intake; at idle the engine cannot tolerate the dilution.