Diagnóstico / Códigos de avería
Exhaust Gas Recirculation (EGR) Flow Excessive
The ECU detected more EGR flow than commanded, usually from an EGR valve stuck open or a faulty position sensor.
Qué significa este código
P0402 on the Mercedes Sprinter VS30 is the opposite of P0401: the ECU sees more recirculated exhaust flow than it commanded. On the OM642 this typically happens when the EGR valve sticks open (often partway, jammed by carbon), or when the position sensor misreports the valve's state. Too much EGR flow dilutes the intake charge, causing rough running, hesitation, and sometimes a smoky idle. The ECU sets P0402 and illuminates the check engine light. The fix is usually cleaning or replacing the EGR valve so it seats and meters properly again, plus verifying the position sensor and control circuit.
Descripción oficial
- EGR flow (high pressure) too high.
Síntomas
- Rough idle or stumbling
- Hesitation on light throttle
- Check engine light
- Smoky or sooty idle
- Minor power loss
Advertencia — revísalo pronto
The ECU detected more EGR flow than commanded, usually from an EGR valve stuck open or a faulty position sensor.
Causas posibles
- EGR valve stuck partially open (carbon)
- Faulty EGR position sensor over-reporting flow
- EGR actuator control fault
- Failed valve return spring/mechanism
- Wiring/connector fault to the EGR valve
Pasos de diagnóstico
- Scan and record all codes; note related codes (P0401, P0299).
- Read freeze-frame for EGR commanded vs. actual position.
- Command the valve closed and confirm it fully seats (actual position returns to zero).
- Remove and inspect the valve for carbon holding it open.
- Test the position sensor and actuator against spec.
- Clean or replace the EGR valve; verify proper seating after repair.
Reparaciones recomendadas
- Clean or replace a carbon-clogged EGR valve and clear the passages.
- Force a regeneration, or replace the DPF if it is aged or damaged.
- Replace faulty differential-pressure, NOx, or exhaust-temperature sensors.
- Repair the SCR/AdBlue dosing system or refill with correct-quality DEF.
- Fix upstream combustion faults that prevent proper regeneration.
Piezas que podrías necesitar
- EGR valve~$200–$500
- EGR valve gasket/seal kit~$15–$40
Preguntas frecuentes
Why would the EGR flow be too high?
Usually the valve is stuck open — carbon prevents it from fully closing, so exhaust keeps flowing into the intake when it shouldn't. A failing position sensor can also make the ECU think flow is excessive.