Diagnostic: Check Engine Light on Mercedes-Benz - Causes and Costs

The orange check engine light on a Mercedes-Benz (A-Class, C-Class, E-Class, GLA, GLC) indicates that the onboard computer has recorded one or more faults. Depending on petrol (M264, M282) or diesel (OM654, OM608) engines, common causes and costs differ.

Mercedes petrol (M264, M282)

On Mercedes petrol engines, the check engine light often comes on due to a faulty lambda sensor, a degraded catalyst or a clogged EGR valve. Worn spark plugs and coils can trigger the warning. An evaporative system fault (canister) can generate codes with no direct impact.

Mercedes diesel (OM654, OM608)

On Mercedes diesel engines, the check engine light is frequently linked to a saturated particulate filter (DPF) or the AdBlue system (level, injector). Clogged lambda sensors and EGR valves also trigger the warning. A faulty turbo may be involved on high-mileage models.

What to do

Drive at moderate speed for a short distance to reach a garage. If the light flashes, reduce engine load immediately. An electronic diagnostic (reading codes) will identify the fault(s). My Auto Check-up helps you prepare your visit for an initial cost estimate.

Order of magnitude for costs

• Lambda sensor: about €150–450. Spark plugs / coils: about €100–350.
• EGR valve: about €350–900. Turbo: about €1,000–2,500 and more.
• DPF regeneration / AdBlue: about €80–200. DPF replacement: about €900–2,000.