Your comprehensive index of every Mercedes-Benz warning light — from the engine management light to the AdBlue system, DPF, oil pressure and transmission warnings. Each light has its own dedicated page with causes, costs and what to do next. Use this index to identify what you're seeing and start your research.
This index collects every documented Mercedes-Benz warning light page on the site — engine management, DPF, AdBlue, oil pressure, coolant temperature, transmission and suspension fault warnings. Each page gives a plain-English explanation, the most common causes with real cost data, and clear guidance on whether you can still drive.
Choose your light from the index below to get the full diagnosis and cost guidance.
These are the most common Mercedes warning lights you'll encounter. Each one has a dedicated page with the specific meaning, common causes ranked by likelihood, real cost data and a clear verdict.
The most generic and most important warning — the ECU has logged a fault. Reading the code is the only way to know what it means.
Typical cost: £90–£5,800 depending on cause
Diesel particulate filter — a common Mercedes diesel issue. Urban driving is the main cause, and ignoring it can be expensive.
Typical cost: £300–£1,800
Mercedes AdBlue system fault — often a failed NOx sensor, heater, or pump. You'll get a countdown before the car refuses to start.
Typical cost: £400–£1,500
Flashing or staying on — the glow plug system has a fault. Usually one or more glow plugs have failed, but sometimes it's the relay or controller.
Typical cost: £150–£600
Restricted performance — the ECU has cut power to protect the engine or emissions system. The stored code tells you why.
Typical cost: £90–£5,800
For a complete list of engine-specific symptoms, see the symptom index or the fault code directory.
These warnings relate to oil, coolant and battery — stopping or acting immediately can save the engine from catastrophic damage.
Low oil pressure — stop the car immediately and check oil level. Driving with this light on can destroy the engine in minutes.
Severity: Catastrophic
Engine overheating — stop safely and check coolant level. A common cause is a failed water pump or coolant leak.
Typical cost: £400–£1,200
Charging system fault — the alternator is not charging the battery. The car will run on battery power until it dies.
Typical cost: £400–£800
Mercedes drivetrain and suspension warnings — transmission, Airmatic and 4MATIC system faults. These can be expensive, so early diagnosis matters.
Mercedes 7G-Tronic or 9G-Tronic transmission fault — often valve body or conductor plate failure. Get the code read.
Typical cost: £800–£3,500
Airmatic suspension system fault — compressor, valve block or air spring failure. Common on E-Class, S-Class and GLE.
Typical cost: £400–£2,200
Mercedes parts and labour baselines sit at a 70% repair-to-value threshold — meaning if the cost of a repair exceeds 70% of the vehicle's market value, we consider scrapping or selling the vehicle as a serious alternative. Each warning light page applies this threshold with a worked example for that specific fault. For more detail, see the repair-replace-scrap framework and the repair-vs-replace calculator.
| Warning Light | Typical Cost Range | 70% Threshold Flag |
|---|---|---|
| Engine Management Light | £90–£5,800 | ✅ Depends on cause |
| DPF Warning Light | £300–£1,800 | ⚠️ Watch on older vehicles |
| AdBlue Warning | £400–£1,500 | ✅ Safe on most |
| Oil Pressure Warning | £800–£5,800 | 🔴 Scrap if engine damaged |
| Coolant Temperature Warning | £400–£1,200 | ✅ Safe |
| Transmission Fault Warning | £800–£3,500 | ⚠️ Watch on sub-£5k cars |
Full model-specific cost guidance on the cost by model ranking page. For engine-specific reliability data, see the Engine Failure Index.
This index lists every warning light page we've built. If you don't see your exact light here, use the Diagnostic Wizard — it will ask you what you're seeing and where it's appearing, and suggest the most likely pages.
It can be a £90 fuel filter or a £5,800 timing chain — the message itself tells you nothing about the cost. That is why we always recommend reading the fault code before accepting any quote. See our fault code directory to look up what your specific code means.
If the light is amber and the car is not in limp mode, a sustained motorway run may clear it. If it's flashing or you're in limp mode, have it diagnosed. Ignoring a DPF warning can lead to a full DPF replacement or, in some cases, engine damage.
Recon supply costs for Mercedes engines start at £1,800 for an OM651 and can exceed £10,000 for a V8 AMG engine. Full engine replacement costs by engine code are on the replacement cost by engine code page.
Every Light Has Its Own PageNot a generic list — each warning gets a dedicated diagnosis.
Real Cost DataEvery figure in every page is tagged to its source.
15+ Vetted Mercedes SpecialistsEvery route ends with someone who diagnoses these daily.
100% IndependentNo sponsors, no manufacturer influence.
Browse the index above or start with the Diagnostic Wizard to identify your light.
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