The ECU has detected that the exhaust gas recirculation (EGR) system is flowing too much exhaust gas – the mirror image of P0401. Often caused by a stuck-open EGR valve, a faulty position sensor, or a leaking vacuum line. We rank the causes cheapest-first so you can avoid replacing the valve unnecessarily.
P0402 means the EGR valve is letting too much exhaust gas into the intake manifold. On Land Rover diesels – especially 204DTD Ingenium and 306DT V6 – this is most often caused by a sticking EGR valve that won't close fully, a faulty position sensor, or a vacuum system fault. Ignoring it can lead to rough idling, poor performance, and increased fuel consumption, but the fix is often straightforward and cheap.
Do not replace the EGR valve before trying a clean and checking the vacuum system. Follow the cheapest-first diagnostic order below.
The EGR system recirculates a small amount of exhaust gas back into the intake manifold to reduce NOx emissions. The ECU controls the EGR valve – either via vacuum or an electric actuator – and monitors its position (or inferred flow) using a sensor. P0402 is set when the ECU sees that the actual EGR flow (or valve position) is greater than the commanded value for a set period. This indicates excessive flow – the valve is not closing fully when it should. The most common cause is carbon build‑up that prevents the valve from seating properly, but it can also be caused by a faulty position sensor, a vacuum leak that pulls the valve open, or debris lodged in the valve. On Land Rover engines, the 204DTD and 306DT are both prone to EGR issues, and P0402 is often the first sign that the valve is sticking or failing.
Ordered by how often each turns out to be the real culprit – with typical fitted cost against each, so you can sanity‑check any quote you've been given.
| Cause | Likelihood | Typical Cost (fitted) | Notes |
|---|---|---|---|
| Carbon build‑up causing valve to stick open | Very High | £100–£250 (clean) | Most common – cleaning the valve resolves it |
| Faulty EGR position sensor (integrated or external) | High | £150–£400 | Sensor gives false high position reading |
| Vacuum leak or faulty vacuum solenoid (on vacuum‑operated EGR) | Medium | £50–£200 | Cheap to fix – often a split hose |
| Debris or foreign object in the valve | Medium | £100–£300 (clean) | Less common, but can cause valve to jam |
| EGR valve internal failure (seized motor or damaged actuator) | Low | £500–£1,500+ | Least common – replacement needed |
Cost figures [PATTERN DATA] – indicative independent‑specialist pricing based on known failure patterns for Land Rover diesel engines.
Read the EGR position sensor data. If the valve is commanded closed but the position reading stays high, the valve is stuck open.
Inspect hoses for cracks, leaks, or disconnections. A simple hose repair often resolves the code.
Remove the valve and clean with carburettor cleaner. This resolves the majority of P0402 cases.
Check for blockages that might force the valve open – cleaning or replacing may be required.
If the valve is mechanically seized or the motor is dead, replacement is necessary.
Use our diagnostic wizard to step through the same logic, or confirm your engine with the registration lookup first.
Yes, but it's not ideal. P0402 itself isn't an emergency – a stuck-open EGR valve won't cause immediate engine failure. However, driving with excessive EGR flow can lead to rough idling, poor throttle response, increased fuel consumption, and eventually carbon build‑up in the intake manifold, which can cause more serious issues. If the code is accompanied by limp mode or black smoke, get it checked promptly. It's safe to drive gently to a specialist, but don't ignore it for months – the carbon deposits will only get worse.
Yes, for short distances and gently. It won't cause immediate breakdown, but it can lead to increased emissions, reduced fuel economy, and carbon build‑up. If the engine goes into limp mode or you see black smoke, get it checked promptly.
No – in most cases, simply cleaning the valve and pipework resolves the issue. Replacement is only needed if the valve is physically seized or the motor is dead. Follow the diagnostic order above to avoid an expensive misdiagnosis.
Only temporarily. The code will return if the flow is still excessive. Clearing it also wipes freeze‑frame data that would help a specialist diagnose the root cause.
Expect 1–2 hours of diagnostic time at an independent JLR specialist – around £100–£200, often offset against the repair if you proceed with them.
For the 204DTD Ingenium, cleaning the EGR valve is the most common and cheapest fix – it resolves the code in over 70% of cases [PATTERN DATA]. A simple carbon clean often does the trick.
Cheapest‑First AlwaysWe rank causes by likelihood and cost, not by what's profitable to quote.
Honest About CostWhere a fault is usually cheap to fix, we say so plainly.
12 Vetted JLR SpecialistsDiagnostics carried out by people who work on these daily.
100% IndependentNo sponsors, no manufacturer influence.
Compare diagnostic and repair quotes from our vetted specialist network.
COMPARE QUOTES NOW → RUN THE DIAGNOSTIC WIZARD