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P0402 Exhaust Gas Recirculation Flow Excessive Detected

Too much exhaust gas is entering the intake — typically an EGR valve stuck open, which makes the engine idle badly.

Emissions

The opposite of P0401. Exhaust gas is inert, so too much of it at the wrong time displaces the air and fuel the engine needs. Because idle is the condition where EGR should be closed entirely, a valve stuck open shows up as a rough, stumbling idle — this code usually comes with symptoms you can feel, unlike P0401.

Diagnose P0402 on your specific vehicle Add your year, make and model for ranked causes, repair videos and the exact parts you need

Can I keep driving?

Driveable

Yes, but expect rough idle and possible stalling at stops.

How serious

Moderate. Stalling in traffic is a genuine nuisance and a mild safety concern.

Symptoms you'll notice

What causes P0402

Ordered by what to check first — how likely each cause is, weighed against what it costs to rule out. Working down the list in order is what stops you replacing an expensive part to fix a cheap problem.

01

EGR valve stuck open

Carbon deposits on the valve seat stop it closing fully, so exhaust flows constantly. The most common cause and often cleanable.

02

Failed EGR valve diaphragm or solenoid

A ruptured diaphragm or a solenoid stuck energised holds the valve open regardless of command.

03

Faulty DPFE or EGR position sensor

A sensor over-reporting flow sets this code even with a correctly operating valve.

04

Vacuum control fault

A control solenoid stuck passing vacuum keeps a vacuum-operated valve open at idle.

05

Damaged EGR gasket

A blown gasket between valve and manifold allows uncontrolled flow past a valve that is closing correctly.

How to diagnose it

  1. Remove the EGR valve and check whether it seats fully and whether carbon is holding it open.
  2. With the engine idling, check whether the valve is open when it should be closed.
  3. Compare commanded EGR position against actual on live data.
  4. Inspect the gasket and mounting surface for damage.
  5. On vacuum systems, check whether vacuum is present at the valve at idle when it shouldn't be.

Parts you might need

Tools for the job

Related trouble codes

Get the parts list for your vehicle Ranked causes, tutorials and live part prices for your exact year, make and model

Fitment matters. Causes and parts above are the common cases for P0402 across vehicles. The specific part numbers, procedures and torque specs vary by year, make, model and engine — always confirm against service data for your vehicle before buying parts or starting work.