P0402 fault code: Exhaust Gas Recirculation Flow Excessive Detected
Last updated · OBDCode UK editorial
Excessive EGR flow is not, on its own, an order to stop at the roadside. Drive with care to a garage. Stop if the engine management light flashes, the engine judders badly, or you feel unwell while idling.
Can I DIY?
Caution — conditions apply. We do not publish DIY repair or strip-down steps for this code on this page. Read codes and observe only; leave the repair to a qualified garage.
Some checks may be possible for a careful DIY driver with the right tools and a safe place to work. Stop if anything feels beyond your skill or kit.
Never idle in a closed garage to read codes — an open door is not enough. CO is odourless and can kill. Run diagnostics in open air. Headache or nausea with exhaust smell: get fresh air and stop.
What does P0402 mean?
P0402 is a generic (SAE standard) powertrain code reported by your car’s engine control unit. It sits in the P04xx block, which covers auxiliary emission controls. The stored description is “Exhaust Gas Recirculation Flow Excessive Detected”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.
How to diagnose P0402 yourself
- Confirm P0402 and freeze-frame: Scan with an OBD-II reader while stationary in open air. Note whether P0402 is current or pending, freeze-frame rpm, load and coolant temperature, and every other stored code from that scan. Stop if: The engine management light is flashing, or you intend to strip the inlet to reach the valve.
Park safely and switch off before locating the socket. Its position varies, so use the vehicle handbook and never force or dismantle trim. - Keep the stored codes for the garage: Photograph or write the full code list and freeze-frame. Do not clear P0402 to ‘see if it comes back’ before a technician has seen it. Do not idle in a closed garage to reproduce the fault. Stop if: You feel dizzy or sick, the light starts flashing, or the next step in your mind is to remove the EGR valve.
Will P0402 fail an MOT?
An illuminated engine management light is a Major defect at MOT until the lamp stays off. Because EGR is part of emissions control, a garage may also need to re-check the exhaust emissions test after repair.
Before booking your test, check what usually fails on your car: see our MOT pass rates by make and model, built from 33.1 million DVSA tests.
What the MOT data says
These figures are copied from the MOT fail cohort for the certificate wording below. They are not a diagnosis of this car.
Certificate wording: “Exhaust gas recirculation valve Emission control equipment fitted by the manufacturer missing, obviously modified or obviously defective”.
Of 601 Class 4 vehicles that failed a 2024 MOT on that wording, 1.5% (95% CI 0.8–2.8) failed on the same wording again in 2025. The not-tested gap versus control was 17.6 points.
Related guides
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P0402 — quick answers
Is it safe to drive with P0402?
Drive with care. Excessive EGR flow is not, on its own, an order to stop at the roadside. Drive with care to a garage. Stop if the engine management light flashes, the engine judders badly, or you feel unwell while idling.
Can I fix P0402 myself?
Caution — conditions apply. We do not publish DIY repair or strip-down steps for this code on this page. Read codes and observe only; leave the repair to a qualified garage. Basic tools only — for example a household socket set, tyre gauge, or a consumer OBD reader.
Will P0402 fail my MOT?
An illuminated engine management light is a Major defect at MOT until the lamp stays off. Because EGR is part of emissions control, a garage may also need to re-check the exhaust emissions test after repair.
Fault-code identifiers are standard diagnostic facts. Their explanations and diagnostic guidance on this site are original editorial summaries, not reproduced SAE wording. MOT defect rules reflect the DVSA MOT inspection manual (2026). This page is general guidance for UK drivers, not a substitute for a professional diagnosis.