P0402 on Mercedes-Benz
Exhaust Gas Recirculation Flow Excessive
P0402 on Mercedes-Benz vehicles indicates exhaust gas recirculation flow excessive. Au7o has documented this code across 1 Mercedes-Benz model — most commonly on B-Class. P0402 means the Exhaust Gas Recirculation (EGR) system is flowing too much exhaust back into the intake. The EGR system intentionally routes a small amount of inert exhaust gas into the engine to lower combustion temperatures and reduce nitrogen-oxide emissions, but the flow must be metered precisely. When the PCM determines the flow is excessive — often because the EGR valve is stuck open or letting gas through when it shouldn't — it sets this code. Too much EGR can cause rough idle, stalling, hesitation, and a check engine light. Typical repair costs on Mercedes-Benz range from $200 to $2,500, depending on the specific model and root cause.
Common Causes of P0402
- •EGR valve stuck open or not closing fully
- •Failed or sticking EGR valve diaphragm/solenoid
- •Carbon buildup holding the EGR valve open
- •Faulty EGR position or differential pressure (DPFE) sensor
- •Leaking EGR valve gasket or pintle seat
- •Vacuum control or solenoid fault commanding EGR open
- •Wiring or connector problems in the EGR control circuit
P0402 on Mercedes-Benz by Model
Mercedes-Benz B-Class(1 issue)
- OM651 Diesel DPF and EGR Clogging (B180 CDI / B200 CDI)2013-2019
The 2.2L OM651 diesel in B180 CDI / B200 CDI variants is prone to diesel particulate filter (DPF) blockage and EGR-valve carbon fouling, especially on short urban trips where the exhaust never reaches regeneration temperature. Symptoms include reduced power (limp mode), increased fuel consumption, frequent failed regenerations, and warning lights. Carbon buildup in the EGR valve and intake also causes hesitation and rough running. The OM651 timing chain can also stretch and rattle, compounding diesel reliability concerns.
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View P0402 across all makes →Frequently Asked Questions
What does P0402 mean on Mercedes-Benz?▼
P0402 stands for "Exhaust Gas Recirculation Flow Excessive." P0402 means the Exhaust Gas Recirculation (EGR) system is flowing too much exhaust back into the intake. The EGR system intentionally routes a small amount of inert exhaust gas into the engine to lower combustion temperatures and reduce nitrogen-oxide emissions, but the flow must be metered precisely. When the PCM determines the flow is excessive — often because the EGR valve is stuck open or letting gas through when it shouldn't — it sets this code. Too much EGR can cause rough idle, stalling, hesitation, and a check engine light. On Mercedes-Benz specifically, this code is documented across 1 model.
What causes P0402 on Mercedes-Benz vehicles?▼
Common causes on Mercedes-Benz: EGR valve stuck open or not closing fully, Failed or sticking EGR valve diaphragm/solenoid, Carbon buildup holding the EGR valve open, Faulty EGR position or differential pressure (DPFE) sensor, Leaking EGR valve gasket or pintle seat. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0402 on a Mercedes-Benz?▼
Repair costs on Mercedes-Benz range from $200 to $2,500, depending on the specific model and root cause.
Which Mercedes-Benz models have P0402 documented?▼
Au7o has documented P0402 on 1 Mercedes-Benz model: B-Class.