Mercedes Fault Codes Index — Complete List & Repair Guide
Your complete index of Mercedes fault codes. Find your code, understand what it means, and get clear, practical guidance on what to do next — all backed by real UK repair data.
Your complete index of Mercedes fault codes. Find your code, understand what it means, and get clear, practical guidance on what to do next — all backed by real UK repair data.
This is the complete Mercedes fault codes index. Whether your code is engine-related, transmission, or ABS, you'll find it here — with clear explanations and links to detailed repair guides.
Use the index below to find your code quickly, then click through for full diagnostic and repair guidance.
This index brings together every Mercedes fault code page we've built across the site, organised by system. Each code links to a dedicated guide that explains what the code means in plain English, the most common causes (ranked cheapest-first), real UK repair costs, and clear guidance on whether you can keep driving. All data is drawn from our proprietary 24,650-query dataset and cross-referenced with manufacturer TSBs and workshop consensus [EM-VERIFIED].
If your code isn't listed yet, use the Diagnostic Wizard to narrow down the cause, or check our symptom guides for experience-based diagnosis.
Engine-related codes covering fuel system, sensors, timing, and more.
Timing chain or adjuster issue. Common on M272 and M276 engines.
Timing chain stretch or sensor misalignment. See M272 balance shaft chain.
Common on OM651 and OM642 diesels. Often a clogged filter or failing sensor.
Pressure regulator or fuel return issue. See OM651 balance shaft for related issues.
Electrical fault in the pressure regulator circuit. Often a wiring issue.
Thermostat stuck open. Common on OM642 and M276 engines.
Failing fuel rail sensor. Can trigger P0087/P0088.
Cooling system failure. See engine overheating guide.
Turbo control issue. Common on OM651 and OM642. See turbocharger failure.
Injector or compression issue. See OM646 injector seal.
Common on OM651 and OM642. Vacuum leak or turbo actuator failure.
Fuel, spark, or compression issue. See misfire guide.
Specific cylinder misfire. Often injector or coil pack related.
Battery or alternator issue. See battery warning guide.
Common on OM651 and OM642. Faulty glow plug control module.
Codes related to EGR, DPF, AdBlue, and emissions control systems.
Clogged EGR valve or cooler. Common on OM651 and OM642. See EGR valve cooler.
EGR valve stuck open. Often carbon buildup.
Electrical fault in EGR circuit. Check wiring and connectors.
Failing catalytic converter. Often triggered by underlying engine issues.
Related to turbocharger failure or boost leak.
Common on OM651. Communication error with glow plug module.
Clogged diesel particulate filter. See DPF blockage guide.
AdBlue system issue. Common on OM654.
AdBlue pump or line issue. See AdBlue/SCR failure.
DPF sensor or exhaust leak issue.
Clogged DPF or blocked pressure lines.
Soot overload. Often requires forced regeneration or cleaning.
Electrical fault in DPF pressure sensor circuit.
Codes related to automatic and manual transmissions, including 7G-Tronic and 9G-Tronic.
Generic transmission fault. See 7G-Tronic gearbox faults.
Common on 7G-Tronic and 9G-Tronic. Speed sensor failure.
Sensor or wiring fault. Can cause harsh shifting.
Similar to turbine speed sensor. Check transmission fluid level.
Internal mechanical fault. Often requires valve body or clutch pack repair.
Electrical fault in transmission solenoid. See 7G-Tronic gearbox faults.
Common solenoid failure. Can cause delayed or harsh shifting.
Similar to P0750. Check transmission fluid and electrical connectors.
Common on older Mercedes transmissions.
Check for stuck solenoid or wiring fault.
Codes related to wiring, sensors, and CAN bus communication.
CAN bus communication fault. Often caused by wiring issues or ECU failure.
Transmission control module communication loss.
Common on older Mercedes. Check wiring and battery voltage.
Can be caused by battery drain or wiring corrosion.
Often linked to battery or CAN bus issues.
Battery or alternator issue. See battery warning guide.
You'll need a Mercedes-compatible OBD-II scanner. Plug it into the diagnostic port (usually under the dashboard) and read the codes. Some codes are manufacturer-specific and may require a Mercedes STAR diagnostic tool.
"P" stands for Powertrain — these codes relate to the engine, transmission, and emissions systems. Other prefixes include "C" (Chassis), "B" (Body) and "U" (Network/Communication).
Yes, using a code reader or disconnecting the battery can clear codes. However, the code will return if the underlying fault isn't fixed. Clearing codes also erases freeze-frame data that a specialist could use to diagnose the issue.
P0087, P0088, P0299, P0401, P2002, and U0100 are among the most common on Mercedes diesels. Each has a dedicated page in this index with detailed repair guidance.
It depends on the code. Some codes (like P0562 for low voltage) are safe for short journeys, while others (like P0217 for overheating) require immediate attention. Each code page includes specific drivability guidance.
Complete IndexEvery Mercedes fault code page on this site, organised by system.
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