A code that signals the exhaust gas recirculation (EGR) system is flowing too much exhaust gas back into the intake. On Jaguar diesel engines, this often points to a stuck-open EGR valve, a faulty EGR position sensor, or a blocked EGR cooler. Ignoring it can lead to reduced performance and eventual engine damage.
P0402 means the engine control unit (ECU) has detected that the exhaust gas recirculation (EGR) flow rate is higher than commanded. On most Jaguar diesel engines - from the Ingenium AJ200D to the 3.0 TDV6 - this is typically caused by a stuck-open EGR valve, a faulty EGR position sensor, or carbon buildup in the EGR system. The fix can range from a £150 cleaning to a £600+ EGR valve or cooler replacement.
Do not ignore P0402. Excessive EGR can cause poor combustion, leading to increased soot and potential DPF blockage.
In a modern Jaguar diesel, the exhaust gas recirculation (EGR) system reduces nitrogen oxide (NOx) emissions by recirculating a portion of exhaust gas back into the intake manifold. The ECU controls the EGR valve to regulate the flow rate based on engine load, speed, and temperature. P0402 is triggered when the ECU detects that the actual EGR flow is higher than the commanded flow - meaning the valve is allowing too much exhaust gas into the intake. This can happen because the EGR valve is stuck open due to carbon buildup, the EGR position sensor is faulty, or the EGR cooler is blocked. The code is common on Ingenium diesel engines in the XE and XF, as well as the 3.0 TDV6 in the XF and F-Pace. The underlying cause is almost always related to the EGR system, making it a code that demands systematic diagnosis.
If you experience a loss of power and see black smoke, arrange a diagnostic check immediately.
Based on real diagnostic patterns from Jaguar specialists. The order reflects both likelihood and typical repair cost.
| Cause | Likelihood | Typical Cost (Fitted) | Notes |
|---|---|---|---|
| Carbon buildup on EGR valve | High | £150–£350 | Valve may be stuck partially open; cleaning often resolves the issue |
| Faulty EGR position sensor | Medium | £180–£400 | Sensor misreads valve position, causing incorrect flow calculations |
| EGR valve stuck open | Medium | £400–£700 | Valve may need replacement if cleaning fails |
| Blocked EGR cooler | Medium | £500–£900 | Carbon buildup in the cooler can restrict flow; common on high-mileage 204DTD units |
| Faulty EGR solenoid or vacuum line | Low | £150–£300 | Vacuum leak or solenoid failure can cause uncontrolled flow |
| Wiring or ECU communication fault | Low | £100–£400 | Corrosion or a bad connection can cause intermittent faults |
Cost figures [PATTERN DATA] - indicative independent‑specialist pricing, not drawn from our engine replacement dataset.
A competent Jaguar specialist will follow this order to avoid misdiagnosing an expensive EGR valve replacement.
Using diagnostic software, read the commanded vs actual EGR valve position. A significant discrepancy often indicates a stuck valve or sensor issue.
A visual inspection of the EGR valve can reveal carbon deposits. Cleaning the valve and the intake ports is often the fix.
A blocked cooler can restrict flow; a pressure test or visual check can confirm this.
Check for vacuum leaks and test the solenoid operation. A cheap repair if found.
If cleaning fails and the sensor is confirmed working, replacement is the final step.
Our diagnostic wizard walks the same order, or use the registration lookup to confirm your engine.
Conditionally, yes - but only to get it directly to a garage. P0402 is not an immediate engine-destroying fault like low oil pressure. However, driving with excessive EGR flow can cause poor combustion, leading to increased soot production, which can clog the DPF and EGR cooler over time. More critically, if the code is caused by a stuck-open EGR valve, continued driving can lead to a significant loss of power and increased fuel consumption. If the car has entered limp mode, it's unsafe for motorway driving due to lack of power. Have it recovered or drive it gently to a specialist.
It means the ECU has detected that the EGR valve is allowing too much exhaust gas into the intake. This is often due to carbon buildup, a stuck valve, or a faulty position sensor.
Conditionally, yes - but only to get it directly to a garage. Avoid heavy acceleration and long journeys, as excessive EGR flow can lead to poor combustion and increased soot, which can damage the DPF. If the car is in limp mode, have it recovered.
It can be. While it may be resolved with a simple cleaning, it could also indicate a failing EGR valve or cooler that needs replacement. Immediate diagnosis is recommended.
The cost ranges from about £150 for a cleaning to £400–£900 for a full EGR valve or cooler replacement. Diagnostic time is typically 1–2 hours.
Only temporarily. The code will return as soon as the ECU detects the flow discrepancy again. Clearing it also destroys freeze‑frame data that helps diagnosis.
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