P0402: Exhaust Gas Recirculation (EGR) Flow Excessive

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.

• EGR flow (high pressure) too high.

• Rough idle or stumbling
• Hesitation on light throttle
• Check engine light
• Smoky or sooty idle
• Minor power loss

• 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

1. 1Scan and record all codes; note related codes (P0401, P0299).
2. 2Read freeze-frame for EGR commanded vs. actual position.
3. 3Command the valve closed and confirm it fully seats (actual position returns to zero).
4. 4Remove and inspect the valve for carbon holding it open.
5. 5Test the position sensor and actuator against spec.
6. 6Clean or replace the EGR valve; verify proper seating after repair.

1. 1Clean or replace a carbon-clogged EGR valve and clear the passages.
2. 2Force a regeneration, or replace the DPF if it is aged or damaged.
3. 3Replace faulty differential-pressure, NOx, or exhaust-temperature sensors.
4. 4Repair the SCR/AdBlue dosing system or refill with correct-quality DEF.
5. 5Fix upstream combustion faults that prevent proper regeneration.

• EGR valve~$200–$500
• EGR valve gasket/seal kit~$15–$40